Spectroscopic Imaging Methods
Exhibit Hall 2-3                    Wednesday 13:30-15:30

                  2376.     An Improved Method for Automatic Placement of Spatial Saturation Planes in MR Spectroscopy

Jordan L. Hovdebo1, Lawrence Ryner1,2

1National Research Council Institute for Biodiagnostics, Winnipeg, MB, Canada; 2Physics and Astronomy, University of Manitoba, Winnipeg, MB, Canada

We present a user-friendly application which implements a new algorithm for the automatic placement of spatial saturation planes to conform a magnetic resonance spectroscopy excitation volume to an arbitrarily shaped tissue of interest. The new algorithm is capable of constructing a conformed voxel in a fraction of a second, orders of magnitude faster than previous methods, while achieving comparable coverage of the tissue of interest.

                  2377.     Automatic Prescription of 3D MRSI with Optimal Coverage and Outer Volume Suppression

Eugene Ozhinsky1,2, Sarah J. Nelson1,3

1Surbeck Laboratory of Advanced Imaging, Department of Radiology, University of California, San Francisco, San Francisco, CA, USA; 2UCSF/UCB Joint Graduate Group in Bioengineering, University of California, San Francisco, San Francisco, CA, USA; 3Program in Bioengineering, University of California, San Francisco, San Francisco, CA, USA

Current MRSI protocols require placing a small selected volume (PRESS box) that does not extend past the edges of the brain to avoid artifacts from the subcutaneous fat and sinuses. This significantly limits the area where tumors can be detected. Manual prescription of an MRSI exam is time-consuming and requires operator training, resulting in limited adoption of MRSI in clinical setting, despite significant advantages in it's diagnostic ability. The goal of this project is to develop a technique to automatically prescribe an MRSI exam, while maximizing the coverage of the brain.

                  2378.     Subcutaneous Lipid Suppression Via Variable-Density Spiral Sampling for Full Cortical Coverage in Chemical Shift Imaging

Joonsung Lee1, Borjan Gagoski1, Michale Hamm2, Elfar Adalsteinsson1,3

1Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA; 2Siemens Medical Solutions USA, Inc, Cambridge, MA, USA; 3Harvard-MIT Division of Health Sciences of Technology, Massachusetts Institute of Technology, Cambridge, MA, USA

Estimates of metabolites in the brain using large-FOV CSI are severely hampered by strong interfering lipid signals arising from subcutaneous tissue. A novel approach using variable-density sampling in k-space with accompanying proportional filtering is presented. Healthy volunteers were scanned on a 3T Siemens Trio scanner with a 32-channel head coil. The variable spiral trajectory was implemented with a conventional PRESS excitation of 3-cm thick axial section with a voxel size of 0.47 cc, and FOVxy = 24 cm, FOVz= 6.2cm, in a scan time of 16 min. Even in peripheral regions of the cortex, NAA is distinguishable from the lipids.

                  2379.     INS-PRESS for Functional MRS: Simultaneous With- And Without-Water Suppression Spectral Acquisition on Visual Cortex of Human Brains at 3T

Yi-Yu Shih1, Chun-Jen Huang2, Martin Buechert3, Hsiao-Wen Chung1,2, Yi-Jui Liu4

1Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan; 2Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan; 3Magnetic Resonance Development and Application Center, University Hospital Freiburg, Freiburg, Germany; 4Department of Automatic Control Engineering, Feng-Chia University, Taichung, Taiwan

Interleaved navigator scan (INS) PRESS was used to acquire functional spectra with water suppression, with the non-water-suppressed navigator signal obtain within one single TR. This technique was employed for fMRS of visual stimulation at 3T to analyze the BOLD effects of water and metabolite concentration changes simultaneously. The metabolites, such as NAA, mI, choline, and creatine, can be stably detected (CRLB<10%) after 32 scan averages, some of which correlated with the brain activation pattern (about 2% increment). In addition, the water peak showed consistent change in magnitude, linewidth, and integral value in the primary visual cortex during photic stimulation.

                  2380.     Simultaneous Acquisition of Metabolite and Water Signals in Echo Planar Spectroscopic Imaging

Toru Shirai1, Satoshi Hirata1, Yukari Yamamoto2, Yoshitaka Bito1

1Central Research Laboratory, Hitachi, Ltd., Kokubunji, Tokyo, Japan; 2Advanced Research Laboratory, Hitachi, Ltd., Kokubunji, Tokyo, Japan

We propose a technique for simultaneous acquisition of metabolite and water signals in Echo Planar Spectroscopic Imaging (EPSI). The pulse sequence of this technique includes three CHESS pulses whose amplitude is switched alternately in accordance with phase encoding steps to reverse the polarity of the water signal. The metabolite signal is separable from the water signal, because the water signal is shifted to the left and right of the reconstructed image. The results of healthy volunteer experiments showed that this technique was effective in suppressing the water signal, which suggests the usefulness of the proposed method.

                  2381.     Proton MR Spectroscopy Using Short TE PRESS Without Water Suppression. in Vivo Application to Rat Brain at 7 Tesla

Wolfgang Dreher1,2, Ekkehard Küstermann1,2, Dieter Leibfritz1,2

1University of Bremen, FB2 (Chemistry), Bremen, Germany; 2Center for Advanced Imaging, Bremen, Germany

It is shown that water suppression is not required to measure high quality proton spectra of the rat brain in vivo using an optimized short TE (TE=10 ms) PRESS sequence on a modern 7 Tesla animal scanner. Remaining gradient induced sideband signals are avoided by adding online two data sets acquired with opposite gradient directions and opposite offset frequencies. Data analysis is either performed without separating water and metabolite signals or after automatic water elimination in the time domain, e.g. by using the matrix pencil method. The presented study is another step to make water suppression obsolete for proton MRS.

                  2382.     Clinical Double Quantum Filtered Lactate Spectroscopy of Leg Ischemia and Non-Hodgkins Lymphoma in 3D

Eric Albert Mellon1, Seung Cheol Lee1, Sungheon Kim2, Ravinder Reddy1, Jerry D. Glickson1

1Radiology, University of Pennsylvania, Philadelphia, PA, USA; 2Radiology, New York University, New York, NY, USA

Lactate is an important biomarker of ischemia, malignancy and cancer response to treatment. But, MR lactate mapping has been difficult due to the overlapping 1.3ppm lipid resonance. Here, using clinical 3T MRI hardware, a combination of selective Multiple Quantum Coherence (SelMQC) with 2D phase and 1D Hadamard encoding (HDMD-SelMQC-CSI) selects lactate. Hadamard selection is demonstrated in the non-Hodgkins lymphoma (NHL) of a patient. Lactate is then imaged in a human NHL in only 5 minutes. Also, increases in lactate are shown during muscle ischemia. This technique is now open for identification of tumor response to therapy and studies of ischemia.

                  2383.     High-Resolution NMR Spectra of Heterogeneous Biological Tissues Via Intermolecular Single-Quantum Coherences

Yuqing Huang1, Zhong Chen1,2, Shuhui Cai1, Jianhui Zhong2

1Physics Department, Xiamen University, Xiamen, Fujian, China; 2Radiology and Biomedical Engineering, University of Rochester, Rochester, NY, USA

In in vivo NMR study, inhomogeneous line broadening due to magnetic susceptibility gradients and intensive water signal often leads to severe spectral peak overlapping and weak signal obstructing. In this abstract, a new pulse sequence based on intermolecular single-quantum coherences (iSQC) was presented for high-resolution spectra from biological tissues. Several heterogeneous biological samples were measured to test the feasibility of the pulse sequence. The experimental results indicate that the method is a useful tool of high-resolution MRS for heterogeneous biological samples.

                  2384.     Multiple Spin Echo Spectroscopic Imaging of Glutamate and Glutamine (Glx)

Atiyah Yahya1,2, B. Gino Fallone1,2

1Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada; 2Department of Oncology, University of Alberta, Edmonton, Alberta, Canada

Collective levels of glutamate and glutamine (Glx) are of value in the study of many diseases. In-vivo levels of Glx can be assessed by spectroscopic imaging. The turbo spectroscopic imaging (TSI) technique has shown to be useful for the fast acquisition of signal from non-coupled protons from multiple slices. TSI is not applicable to coupled spins because the J-modulation as a function of time can cause spatial misregistrations. In this work, a TSI sequence is presented that can yield high signal, from the C2 protons of Glx. The efficacy of the sequence was verified on phantoms and on brain.

                  2385.     MR Imaging and Spectroscopy of a Bioartificial Pancreas In Vitro and In Vivo at 11.1 T Using Implantable Probes

Nelly A. Volland1, Thomas H. Mareci2,3, Nicholas E. Simpson4,5

1Biomedical Engineering, University of Florida, Gainesville, FL, USA; 2Biochemistry and Molecular Biology, University of Florida, Gainesville, FL, USA; 3National High Magnetic Field Laboratory, University of Florida, Gainesville, FL, USA; 4Medicine, University of Florida, Gainesville, FL, USA; 5McKnight Brain Institute, University of Florida, Gainesville, FL, USA

Introduction: Non-invasive in vivo imaging and spectroscopy of a bioartificial pancreas using an implantable inductively-coupled coil system at 11.1T is discussed. Methods: An implantable coil was constructed, coated, integrated with the macroconstruct, and implanted in a mouse peritoneal cavity. The coil-construct assembly was inductively-coupled to an external coil and tested in vivo. Results: In vivo studies showed sensitivity improvement of 2.35 over a surface coil when the average distance between the two coils was 0.64cm. Choline spectra, 19F images and spectra were also acquired. Conclusion: An implantable system was successfully tested and used to monitor a bioartificial pancreas in vivo.

 
Spectroscopy Quantitation
Exhibit Hall 2-3                    Wednesday 13:30-15:30

                  2386.     Mapping Glucose and Lactate Concentrations with Microliter Resolution in Rat Brain Using Short-Echo-Time Spectroscopic Imaging

Vladimir Mlynarik1, Cristina Cudalbu1, Hanne Frenkel1, Rolf Gruetter1,2

1Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; 2Departments of Radiology, Universities of Lausanne and Geneva, Switzerland

Creatine, glucose and lactate concentration maps were obtained in rat brain at different plasma glucose concentrations (up to 15 mmol/L) using short-echo-time proton spectroscopic imaging. The technique was capable to detect relatively small changes in brain glucose and lactate concentrations with changing plasma glucose level. The brain glucose concentrations at different plasma glucose concentrations were in good agreement with reported values obtained by in vivo 13C spectroscopy. The study demonstrated feasibility of mapping spatial distribution and changes with physiology of low-concentration metabolites or those having complicated spectral patterns.

                  2387.     Resolution Enhancement of Brain Glutamate, Glutamine and Myo-Inositol by PRESS (TE1, TE2) = (37, 63) Ms at 7T

Changho Choi1, Ivan Dimitrov1,2, Deborah Douglas1, Halima Hawesa1

1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA; 2Philips Medical Systems, Cleveland, OH, USA

PRESS echo time dependences of glutamate (Glu), glutamine (Gln), N-acetylaspartate (NAA), myo-inositol (mI) and GABA were investigated for TE1 and TE2 between 30 and 200 ms, with density-matrix simulation incorporating the shaped slice-selective radio-frequency and gradient pulses, at 7T. The numerical calculation indicated that the Glu and Gln C4-proton resonance peaks can be clearly differentiated at (TE1, TE2) = (37, 63) ms, with excellent suppression of the macromolecule background signals and the neighboring abundant NAA aspartate resonances. The multiplets of mI at ~3.52 and 3.61 ppm can also be well defined with these echo times. In vivo human brain spectra from the prefrontal and left frontal lobes that were obtained with this optimized PRESS are discussed in comparison with spectra obtained with short-TE STEAM (TE = 14 ms, TM = 19 ms) and the recently-reported optimized STEAM sequence times (TE = 74 ms, TM = 68 ms). A preliminary in vivo study demonstrates the improved performance of the optimized PRESS compared to STEAM.

                  2388.     T2 Correction and Quantitation Method on Highly Resolved 2D Constant Time 1H Spectra in Human Brain Using 2D FT of Shared Time Domain Data

Hidehiro Watanabe1, Nobuhiro Takaya1, Fumiyuki Mitsumori1

1Environmental Chemistry Division, National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan

A T2 correction and quantitation method on CT-PRESS spectra using 2D FT of shared time domain data is proposed. Spectra with varied Tct are generated by reconstruction of several parts of the total time domain data. Then, T2 is calculated by curve-fitting of peak volumes on those spectra. Coil-loading factors were considered by the internal water reference method for quantitation. T2 of a Cr singlet calculated by this method was in good agreement with T2 by the conventional 1D method. After quantitation protocol, concentration of glutamate was calculated as 8.0 mM which is in good agreement with reported values.

                  2389.     New MR-Scanner Independent B1 Field Mapping Technique

Vaclav Brandejsky1, Olof Leinhard Dahlquist1,2, Eva Lund1, Peter Lundberg1,2

1Department of Medical and Health Sciences, Linköping University, Linköping, Sweden; 2Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden

The aim of this work is to implement a novel, scanner-independent, precise B1 field measurement method, which would make it possible to acquire both the magnitude and the phase of the RF-signal. It is particularly important to use these methods for the detection of the X-nuclei, such as 31P, for which the limited detection sensitivity makes mapping using direct detection in a scanner inconvenient, highly unpractical, or even impossible.

                  2390.     Ongoing Dual-Angle Measurements for the Correction of Partial Saturation in 31P MR Spectroscopy

Orlando Lopez1, Damian J. Tyler2, Kieran Clarke2, Edward Lakatta3, Richard G. Spencer1

1Magnetic Resonance Imaging and Spectroscopy Section, National Institute on Aging/NIH, Baltimore, MD, USA; 2University of Oxford, Department of Physiology Anatomy and Genetics, Oxford, UK; 3Laboratory of Cardiovascular Science, National Institute on Aging/NIH, Baltimore, MD, USA

Use of short repetition time (TR) relative to metabolite T1’s is common in 31P MRS of biological samples. However, spectral resonances acquired with short TR values exhibit saturation effects that have traditionally been corrected using saturation factors. This approach does not account for the chemical exchange exhibited in biological systems which may lead to large errors. Here, we describe an approach to metabolite quantification based on performing ongoing dual&#61485;angle measurements (O-DAM) in the setting of chemical-kinetic changes. Results showed that O-DAM correction can permit accurate monitoring of metabolite concentrations even in the setting of chemical exchange and changing chemical-kinetic parameters.

                  2391.     Selectivity Enhancement of Glutamine in Human Brain by Triple Refocusing at 3T: Application to Hippocampus

Changho Choi1, Carol Tamminga2, Ana Stan2, Deborah Douglas1, Perry Mihalakos2, Stephanie Morris2

1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA; 2Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, USA

Proton triple refocusing has been employed for measurement of glutamate (Glu) and glutamine (Gln) in human brain at 3T in vivo. A 60-ms non-space selective 180° RF pulse (bandwidth = 270 Hz), tuned to 2.4 ppm, was applied within PRESS, thereby refocusing only the resonances between 1.3 and 3.5 ppm. Subecho times were optimized, with density matrix simulation, for maximum selectivity of the Gln C4-proton multiplet, which gave (TE1, TE2, TE3) = (23, 74, 18) ms. In vivo tests were conducted on the hippocampus of five healthy volunteers. With LCModel analysis, the concentrations of Glu, Gln and NAA were estimated as 10.5±0.6, 2.8±0.7 and 9.7±-0.6 mM with reference to Cr at 8 mM, with fit standard deviations of 6±2%, 10±2% and 2±1% respectively.

                  2392.     In-Vivo Measurement of Serine in Human Brain by Constant-TE PRESS Difference Editing at 7.0 Tesla

Changho Choi1, Ivan Dimitrov1,2, Deborah Douglas1

1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA; 2Philips Medical Systems, Cleveland, OH, USA

Measurement of serine (Ser) in human brain has been pursued with constant-echo time PRESS difference editing at 7T. Subecho time dependence of the Ser multiplet was investigated for TE1 and TE2 between 20 – 200 ms, using density-matrix simulation incorporating the slice-selective shaped RF and gradient pulses. The simulation indicated that the Ser ~3.96 ppm resonances can be edited by means of difference between PRESS spectra at (TE1, TE2) = (108, 80) and (49, 139) ms, canceling the creatine (Cr) 3.92 ppm signal. An in vivo spectrum obtained from the frontal cortex showed a Ser edited signal clearly. The area of this peak was estimated to be 1.5% with respect to a Cr 3.03-ppm signal, giving 0.4 mM with reference to Cr at 8 mM.

                  2393.     A Systematic Approach for Chemical Quantification in MRSI: Methodological Considerations

Neva M. Corrigan1, Todd L. Richards1, Helen Petropoulos1, Seth D. Friedman2, Stephen R. Dager1

1Radiology, University of Washington, Seattle, WA, USA; 2Radiology, Children's Hospital and Regional Medical Center/University of Washington, Seattle, WA, USA

Magnetic resonance spectroscopic imaging (MRSI) allows for a tremendous volume of data to be produced in a single scan. These data sets, however, can be very cumbersome to process. In this work we evaluate a proposed systematic approach for chemical quantification in MRSI data sets that is capable of making use of the information contained in the data set to increase regional specificity was well as increase the reliability of the calculated chemical concentrations. We demonstrate the benefits of this method by applying it to quantification of lactate during sodium lactate infusion in healthy adults.

                  2394.     Optimized Detection of Glutamate and Glutamine at 1.5 T, 3 T and 4.7 T

Jeff Snyder1,2, Richard B. Thompson3, Alan H. Wilman2,3

1Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany; 2Physics, University of Alberta, Edmonton, Alberta, Canada; 3Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada

The detection of glutamate and glutamine independently via PRESS magnetic resonance spectroscopy is highly dependent on the chosen field strength and echo time parameters. In this study, optimized timing simulations were performed at three field strengths (1.5 T, 3 T and 4.7 T) to minimize the overlap of glutamate and glutamine in the 2.0 – 2.7 ppm range and provide better discrimination. The results of the optimization are applied in vivo at 1.5 T and 4.7 T in the human brain. The best result occurs at 4.7 T, with a maximum calculated overlap of 4%.

                  2395.     31P-MR Investigations of Training Effects on Resting State Concentration of Phosphor Metabolites in the M. Gastrocnemius

Reinhard Rzanny1, Norbert Stutzig2, Alexander Gussew1, Werner Alois Kaiser, Hans-Alexander Thorhauer2, Jürgen R. Reichenbach1

1Medical Physics Group, Institute of Diagnostic and Interventional Radiology, University Clinics Jena, Jena, Germany; 2Institute of Sports Science, Friedrich-Schiller-University Jena, Jena, Germany

A group of six professional volleyball players was investigated by 31P-MRS at 3.0 T before and after a complex training procedure. The estimated PCr/ATP ratios of the medial and lateral head M. gastrocnemius were used to compare trainings effects of a plyometric training and a modified plyometric training including additional applications of EMS pulses. The results indicate lower reduced PCr/ATP ratios for the medial head muscle after the modified plyometric training.This was interpreted as a reduction of the fiber shift from type II to type I by the aditional application of EMS in the training.

                  2396.     Assessment of Relative and Absolute Quantification Methods in Phosphorus Magnetic Resonance Spectroscopy

Jodi E. Miller1,2, Peter C. Williamson2,3, Dick J. Drost1,2

1Imaging, Lawson Health Research Institute, London, Ontario, Canada; 2Medical Biophysics, University of Western Ontario, London, Ontario, Canada; 3Psychiatry, University of Western Ontario, London, Ontario, Canada

Three different 31P MRS referencing methods (external reference, total phosphorus and PCR +ATP) were evaluated by observing coefficients of variance and correlations between methods. In addition, each method was applied to our clinical schizophrenia data to test whether different referencing methods can lead to different significance. The external reference had the highest coefficients of variance and correlations between total phosphorus and PCR + ATP were greatest. Application to our clinical data, revealed the external reference to be the most conservative and total phosphorus the least. When choosing a reference method the possibility of false significant results or overlooking significant results must be considered.

                  2397.     Measurement of Glycine in Human Brain by PRESS at 7.0 Tesla in Vivo

Changho Choi1, Ivan Dimitrov1,2, Deborah Douglas1, Halima Hawesa1

1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA; 2Philips Medical Systems, Cleveland, OH, USA

Glycine (Gly) in human brain has been measured using an optimized PRESS (point-resolved spectroscopy) sequence at 7T. Echo time dependences of the coupled resonances of myo-inositol, choline and threonine were investigated for TE1 and TE2 between 20 and 200 ms with 1 ms increments, using the density matrix simulation incorporating the volume selective radio-frequency and gradient pulses. The numerical simulation indicated that the Gly selectivity is maximized at (TE1, TE2) = (100, 48) ms. LC model fitting was used for in vivo data analysis. The fit standard deviation of Gly was ≤ 8% in all three spectra (scan time ~5 min). The Gly concentration in human brain was estimated to be 0.6, 0.8 and 0.8 mM for the medial prefrontal, fronto-parietal and occipital cortices with reference to creatine at 8 mM, respectively.

                  2398.     MRS 2D Quantification Vs 1D Quantification

Tangi Roussel1, Hélène Ratiney1, Sophie Cavassila1

1Creatis-LRMN, CNRS UMR 5220, Inserm U630, INSA-Lyon, Université Lyon 1, Villeurbanne, France

Many in vivo proton Magnetic Resonance Spectroscopy (MRS) studies led to one dimensional (1D) short echo time spectroscopic signal quantification methods. However, standard in vivo MRS acquisitions in 1D spectroscopy present important limitations. 1D MRS spectra usually present rich in vivo metabolic information through complicated, overlapped spectral signatures with large linewidths, especially at moderate field. Accurate concentration quantification remains problematic especially for coupled metabolites such as ƒ×-aminobutyric acid (GABA), Glutamine (Gln), Glutamate (Glu), myo-inositol (mI) and Taurine (Tau). To overcome these limitations, the two dimensional (2D) spectroscopy, has great potential to unravel of the spectral information. Very few studies on 2D spectroscopic signal quantification were performed. This paper introduces a 2D spectroscopic signal quantification algorithm based on a global fitting procedure using strong prior-knowledge in the time domain and investigates the correlation between parameter estimates occurring in 1D vs 2D quantification.

                  2399.     Simultaneous Quantification of γ-Aminobutyric Acid, Glutamate, and Glutamine at 3T

Peter Sheffield1,2, Michael D. Noseworthy2,3, John Bienenstock2,4

1Medical Sciences, McMaster University, Hamilton, Ontario, Canada; 2Brain-Body Institute, St. Joseph's Healthcare, Hamilton, Ontario, Canada; 3Electrical and Computer Engineering, School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada; 4Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada

An optimization of the STEAM sequence for simultaneous quantification of the coupled GABA/Glutamate/Glutamine spin system at 3T is described. The method was tested in anterior cingulate from normal volunteers. The approach appears consistent as assessed from 4 scans (throughout 1 day) repeated on the same subjects. Although the scan is long (25.6min) it allows measurement of Glu, Gln, and GABA from a standard STEAM sequence.

                  2400.     Proton Metabolite B1–Corrected T1 Mapping in the Human Brain at 3 Tesla

Roman Fleysher1, Lazar Fleysher1, David Hess1, Brian Soher2, Songtao Liu1, Oded Gonen1

1NYU School of Medicine, New York, NY, USA; 2Duke University, Durham, NC, USA

The accuracy of quantitative metabolic assessment in 1H-MRS studies is limited by the unknown B1 distribution and T1. To address both we obtained B1-corrected T1 maps of NAA, Cho and Cr in gray and white matter regions of six volunteer at 3T. 3D 1H-MRS in a new three-point protocol that optimizes the precision of B1–corrected T1 estimates was used. The T1s [mean±SEM] were, NAA: 1233±21, Cr: 1240±18 and Cho: 1115±16 ms. Their histograms from voxels in the VOI in each subject are similar in peak position and shape by better than 4%, representing gratifying T1s reproducibility for each metabolite.

                  2401.     The Impact of SNR on the Reliability of LCModel and QUEST Quantitation in 1H-MRS

Sarah Andrea Wijtenburg1,2, Jack Knight-Scott1,2

1Radiology, Children's Healthcare of Atlanta, Atlanta, GA, USA; 2Biomedical Engineering, University of Virginia, Charlo ttesville, VA, USA

Here, we examine the effect of SNR on the reliability of the frequency-domain LCModel and time-domain QUEST quantification methods for spectra from the human brain. 10 ms TE 1H MRS data were collected from healthy adults on a 1.5 T Siemens Magnetom Sonata MRI system. NAA, Glx, Cre, Cho, and mI were identified, and the SNR calculated for each metabolite in the time and the frequency domain. Based on the stability of the concentration values, these results indicate that NAA and Cr are best fit with LCModel, while Glx, Cho, and mI are best fit with QUEST.

                  2402.     Evaluation of Sensitivity and Reliability of Functional MR Spectroscopy Using Virtual Titration

Chun-Jen Huang1, Yi-Yu Shih2, Yi-Jui Liu3, Hsiao-Wen Chung1

1Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan; 2Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan; 3Department of Automatic Control Engineering, Feng Chia University, Taichung, Taiwan

Functional magnetic resonance spectroscopy (fMRS) has been used to investigate the activation-related metabolic changes of neurons following stimulation. One of the most critical challenges in fMRS is the extremely tiny signal change. In this study, we investigated the ultimate sensitivity level of 1H spectroscopy at 3.0 Tesla and performed fMRS visual stimulation tests to examine the quantitative level of concentration changes in N-acetylaspartate (NAA). We conclude that quantitative analysis of fMRS data seems to allow detection of 0.8% changes ultimately in NAA concentration at 3.0 Tesla, and visual stimulation has the potential to affect the metabolism of NAA.

                  2403.     Robust Phase Correction for 1D NMR Spectra: Application to Fully Automated Quantitation of Whole-Body Adiposity in Less Than 5 Seconds

Jeffrey Tsao1, Brittany Yerby1, Yun Jiang1

1Global Imaging Group, Novartis Institutes for BioMedical Research, Cambridge, MA, USA

Phase correction is a notoriously difficult problem in spectral quantitation, with many solutions being proposed over the years. Here, we discovered a remarkably simple yet robust metric that allows fully automated phase correction in 1D spectroscopy, even in the presence of poor line shapes. We demonstrate the application of this method in combination with a non-localized spin-echo sequence to achieve fully automated spectral quantitation of whole-body adiposity in mice in less than 5 seconds. Results are presented from over 150 measurements from a diet-induced mouse model of obesity.

                  2404.     Separation of EMCL and IMCL in Musculoskeletal 1H MR Spectra by Filter-Diagonalization Method (FDM)

Jyh-Miin Lin1, Shang-Yueh Tsai2

1Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan; 2Department of Electrical Engineering, Chang Gung University, Taiwan

Time domain algorithm is useful to quantify the muscular 1H MR spectra but is less efficient and not frequency-selective. Here we propose to use the Filter-Diagonalization Method (FDM), a frequency-selective time domain algorithm, originally developed for quantum dynamic computation, to separate the extramyocellular lipids (EMCL) and intramyocellular lipids (IMCL). The local basis can extract the metabolite signals in muscular 1H MRS data with economic computational cost. Results from our preliminary study showed, with a properly selected basis, the FDM can reliably separates the near CH2 groups of EMCL(~1.49ppm) and IMCL(~1.28ppm).

                  2405.     Quantitative 2D In-Vivo Spectroscopy Using the ERETIC Method

Alexander Fuchs1, Susanne Heinzer-Schweizer1, Anke Henning1, Peter Boesiger1

1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

A fundamental requirement to use spectroscopy in a clinical setting is the ability to reliably quantify the individual metabolites. While 2D experiments like JPRESS can provide improved spectral separation by dispersing spectral information in an additional frequency dimension the artificially injected ERETIC signal can serve as a stable and well known reference signal. It is shown that the ERETIC reference signal can be readily incorporated into in-vivo 2D spectroscopic experiments, which finally provides the necessary premises for reliable quantification in in-vivo 2D MRS.

                  2406.     Comparision of Metabolite Correlations in 1D and 2D Quantitative Spectroscopy

Alexander Fuchs1, Anke Henning1, Thomas Lange2, Peter Boesiger1

1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland; 2Dept. of Diagnostic Radiology, Medical Physics University Hospital Freiburg, Freiburg, Germany

2D spectroscopy offers the advantage of increased spectral resolution and therefore increases the possibility of fitting even strongly overlapped signals like Glu, Gln or GABA independently. The signals of 18 metabolites were simulated for typical in vivo line widths and spectral separation at 3T. Subsequently the correlations obtained from the Fisher information matrices were compared between a standard singel voxel PRESS, 2D L-COSY and a maximum echo sampled JRPESS sequence. The results clearly show how the correlations decrease and as a consequence the orthongonality of the basis set for the 2D spectroscopic experiments is drastically improved.

                  2407.     Outer-Volume Suppression Pulses to Improve In-Vivo 2D MR Spectroscopy

Roland Kreis1, Daniel Guo Quae Chong1

1Deptartment Clinical Research, University Bern, Bern, Switzerland

Outer-volume-suppression (OVS) pulses have long been used to improve localization in MRS. Recently, they were employed to improve sensitivity of PRESS for lactate that is affected by incomplete J-modulation due to the chemical shift artifact. This is also relevant in 2DJ-spectroscopy – or other 2D sequences involving coherence transfer or refocusing by use of slice selective pulses. It is shown that extending a 2DJ-spectroscopy sequence with OVS pulses ameliorates spin evolution in order to 1) obtain spectra that are closer to those from ideal simulations used in 2D fitting, and 2) offer better cross-peak yield to make them more sensitive.

 
Hyperpolarized C-13 & Other Nuclei
Exhibit Hall 2-3                    Thursday 13:30-15:30

                  2408.     Metabolism of Hyperpolarized 1, 4-13C2-Fumarate in Human Cancer Cell Lines

Anna Gisselsson1, Magnus Kalsson1, Pernille Rose Jensen1, René in 't Zandt1, Georg Hansson1, Mathilde H. Lerche1

1Imagnia AB, Malmö, Sweden

Hyperpolarization of metabolic markers provides a powerful tool to study real time metabolism on a cellular level. To investigate if hyperpolarized fumarate can be used as a marker to study an altered metabolism in cancer, we studied the conversion of 1,4-13C2-fumarate into 1,4-13C2-malate in four human cancer cell lines; breast adenocarcinoma (MDA-MB-231), chondrosarcoma (H EMC-SS) and two prostate cancer lines (PC-3 and DU-145). Conversion of 1,4-13C2-fumarate to 1,4-13C2-malate could be seen in all four cancer lines investigated. The observed difference in conversion rate into 1,4-13C2-malate between cell lines of varying aggressiveness opens up for a potential new method to stage cancer.

                  2409.     Using Spectral-Spatial Saturation RF Pulses to Remove Blood Signals in Hyperpolarized Carbon-13 Metabolic Studies

Kevin Kai-Chi Leung1,2, Albert P. Chen3, Angus Z. Lau1,2, Wilfred W. Lam2, Charles H. Cunningham1,2

1Dept. of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada; 2Imaging Research, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; 3GE Healthcare, Toronto, Ontario, Canada

In tumor metabolic studies that use hyperpolarized carbon-13 compounds and MR spectroscopy, there are metabolic products generated elsewhere in the body that enter the tissue of interest via the blood stream and complicate the analysis of local metabolism. To eliminate the signals of the washed-in [1-13C]pyruvate metabolic products in the kidneys, we employed a spectral-spatial saturation radiofrequency pulse that saturates alanine and lactate but leaves pyruvate undisturbed at the heart region. Using the pulse, we observed lower lactate signals and pyruvate-lactate conversion rates in the kidneys.

                  2410.     Hyperpolarized 13C 3D Metabolic Imaging with Stimulated Echoes for Flow Suppression

Peder E. Z. Larson1, Ralph Hurd2, Adam B. Kerr3, Robert Bok1, John Kurhanewicz1, Daniel B. Vigneron1

1Radiology and Biomedical Imaging, University of California - San Francisco, San Francisco, CA, USA; 2Global Applied Science Lab, GE Healthcare, Menlo Park, CA, USA; 3Electrical Engineering, Stanford University, Stanford, CA, USA

We have developed and applied a novel stimulated echo sequence for hyperpolarized 13C metabolic imaging. The stimulated echo encoding is used with injected [1-13C]-pyruvate to suppress metabolites that are flowing by including a mixing time (1 s) between the encoding and acquisition. Only stationary spins are refocused, thus providing unique information about the mobility of the metabolites. In a mouse prostate cancer model, this method increased the discrimination between tumor and normal tissues based on 13C-lactate detection, highlighting the differences in metabolite flow.

                  2411.     Improved Resolution of 2D and 3D [1-13C] Hyperpolarized MRSI Using a 3-Element Coil and SENSE Reconstruction

Janine M. Lupo1, Peder E. Larson1, Albert P. Chen2, James Tropp3, Esin Ozturk-Isik1, Daniel B. Vigneron1, Ralph Hurd3, Sarah J. Nelson1

1Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA; 2Global Applied Science Lab, GE Healthcare, Toronto, Canada; 3Global Applied Science Lab, GE Healthcare, CA, USA

This study implemented a SENSE acquisition and reconstruction to increase the spatial resolution of 13C MRSI of rats at 3T using a custom-built 3-element receive coil. 13C MRSI data were acquired using a 2D standard phase encoding and 3D phase encoding with flyback spatial trajectories. The 3D flyback 13C MRSI with SENSE allowed for full coverage of a rat body in 16s with a 0.5cc spatial resolution. This technique did not significantly compromise the overall spectral quality of the spectra, resulting in higher SNR than theoretically expected based on the g-factors for labeled pyruvate, lactate, and alanine in most anatomical regions.

                  2412.     Hyperpolarzed 13C-1-Pyruvate Metabolic Imaging of Inflammatory Arthritis

John Dewolfe MacKenzie1, Dirk Mayer1, Yi-Fen Yen2, Shreyas Vasanawala1, James Tropp2, Daniel M. Spielman1

1Radiology, Stanford University, Stanford, CA, USA; 2Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, USA

This preliminary study suggests that pyruvate metabolism may serve as a biomarker of arthritis activity. This study also suggests that arthritis activity may be visualized and quantified with hyperpolarized 13C-1-pyruvate MR spectroscopy.

                  2413.     14 Substrates Are "ready-To-Go" for in Vivo DNP Hyperpolarization Studies

Magnus Karlsson1, Pernille Rose Jensen1, Anna Gisselsson1, Rene in 't Zandt1, Georg Hansson1, Mathilde Hauge Lerche1

1Imagnia AB, Malmö, Sweden

In-vivo metabolism of small 13C labelled molecules can be studied with the DNP-MR technique. However, such studies require substrate concentrations and experimental time windows that deviate significantly from studies using conventional MR techniques. To obtain high enough S/N ratios of metabolites the injected substrates need to be highly polarized at the moment of injection. Here we show the result of an in vivo screen of the spin–lattice relaxation time constants (T1) in healthy mouse with 14 selected highly polarized compounds.This result provides a good basis for the development of pre-clinical and clinical metabolic substrates.

                  2414.     In Vivo Hyperpolarized 13C-MRS of Ethanol-Modulated Pyruvate Metabolism in the Rat

Daniel M. Spielman1, Dirk Mayer1,2, Yi-Fen Yen3, James Tropp4, Ralph E. Hurd3, Adolf Pfefferbaum2,5

1Radiology, Stanford University, Stanford, CA, USA; 2SRI International, Menlo Park, CA, USA; 3GE Healthcare, Menlo Park, CA, USA; 4GE Healthcare, Fremont, CA, USA; 5Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA, USA

Using in vivo 13C-MRS of hyperpolarized pyruvate, we report a two-fold increased rate of rat liver pyruvate-to-lactate conversion in the presence of ethanol, an effect attributable to elevated levels of nicotinamide adenine dinucleotide (NADH) associated with ethanol metabolism in combination with NADH’s role as a coenzyme in pyruvate-to-lactate conversion. In addition to providing a tool to investigate pathologies including alcoholic fatty liver disease and cirrhosis, these results, viewed as an indirect assay of changes in NADH levels, indicate hyperpolarized 13C-pyruvate can potentially be useful for interrogating any of the large number of in vivo metabolic pathways involving the coenzyme NAD+/NADH.

                  2415.     Hyperpolarized 13C MRS in the Rat Brain: Spectral Improvements with 1H Decoupling

Malgorzata Marjanska1, Dinesh K. Deelchand1, Isabelle Iltis1, Pierre-Gilles Henry1

1Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minneapolis, MN, USA

Most in vivo studies using the dynamic nuclear polarization technique to enhance sensitivity of 13C have been utilizing molecules with 13C labeled quaternary carbons. These carbons possess small long-range J-couplings with protons. Here we show that, although 1H-decoupling has little impact on the [1-13C]pyruvate resonance it significantly improves the linewidth and SNR of [1-13C]lactate, [2-13C]pyruvate and [2-13C]lactate.

                  2416.     Simultaneous Multicompound Hyperpolarization by DNP

Kayvan Keshari1,2, David Wilson2, Mark VanCriekinge2, Daniel Vigneron2, Jeffrey Macdonald1, John Kurhnaewicz2

1University of North Carolina, Chapel Hill, NC, USA; 2University of California, San Francisco, USA

Recent studies of hyperpolarized 13C labeled compounds, specifically 13C1-pyruvate, have been used to investigate metabolic processes associated with the Warburg effect. These methods probe one specific pathway, the last step of glycolysis in which pyruvate is enzymatically converted to a number of products. Each of these products is indicative of the flux through the enzyme of choice, for example lactate production demonstrates LDH flux. This study demonstrates, for the first time, the simulataneous hyperpolarization of multiple compounds as well as their injection into an NMR compatible 3D culture system. Multi-compound hyperpolarization can lead to the real time assessment of multiple fluxes simultaneously.

                  2417.     Probing the In Vivo Compartmentalization of Hyperpolarized Pyruvate Using Gadodiamide Induced T1 Relaxation

Eric T. Peterson1, Jeremy W. Gordon2, Krishna N. Kurpad2, Sean B. Fain2, Ian J. Rowland3

1Biomedical Engineering, University of Wisconsin - Madison, Madison, WI, USA; 2Medical Physics, University of Wisconsin - Madison, Madison, WI, USA; 3Radiology, University of Wisconsin - Madison, Madison, WI, USA

The biodistribution of hyperpolarized metabolites is of great importance in hyperpolarized 13C experiments. Spectral imaging can determine the spatial locations of the metabolites; however, the different biological compartments may reside within a single voxel. This work probes the intra and extra cellular compartmentalization of hyperpolarized molecules by using Gadodiamide induced T1 relaxation to increase the relaxation time of the extra cellular components. By quantifying the T1 relaxation before and after Gadodiamide injection, the intra cellular, extra cellular, and intra vascular components of each spectral component may be determined.

                  2418.     Imaging Fluoropyrimidine-Based Cancer Chemotherapy Using 13C Hyperpolarised MR Technology

Yann Jamin1, Simon P. Robinson1, Martin O. Leach1, Thomas R. Eykyn1

1Institute of Cancer Research and Royal Marsden NHS trust, Sutton, UK

The yeast cytosine deaminase (CD) is used in cancer chemotherapy to activate selectively the nontoxic prodrug 5-Fluorocytosine (5-FC) into the toxic antimetabolite 5-Fluorouracil (5-FU) in tumours. Employing Dynamic Nuclear Polarization (DNP) and 13C MRS, we demonstrate that both 5-FC and 5-FU are readily hyperpolarizable, demonstrate long T1 (> 20s, at 11.7T) and a appreciable 13C chemical shift difference of ~ 5ppm. This results encourage further investigation on the use of hyperpolarized 13C MRS to monitor CD-mediated activation of 5-FU in vivo as well as other Fluoropyrimidine-based chemotherapy strategies.

                  2419.     13C MRI Reporter Probe System with Dynamic Nuclear Polarization

Albert P. Chen1, Ralph E. Hurd2, David M. Wilson3, Graham Wright4, Charles H. Cunningham4

1GE Healthcare, Toronto, ON, Canada; 2GE Healthcare, Menlo Park, CA, USA; 3Radiology, UCSF, San Francisco, CA, USA; 4Sunnybrook Health sciences centre, Toronto, ON, Canada

Utilizing dynamic nuclear polarization techniques, a 13C MRI reporter probe system based on hyperpolarized [1-13C] N-acetyl-methionine and acylase I enzyme was developed. De-acetylation of the hyperpolarized substrate by the enzyme was observed with high temporal or spatial resolution in In vitro dynamic MRS and 2D CSI data. In vivo 3D CSI data acquired from normal rats following injection of hyperpolarized [1-13C] N-acetyl-methionine demonstrated no observable metabolic product, suggesting the potential of this reporter system for target MR imaging in vivo.

                  2420.     Non-Invasive Detection of Cell Death in MCF-7 Breast Cancer Cells by Hyperpolarized 13C MRS

Timothy H. Witney1,2, Roberta Napolitano1,3, Mikko I. Kettunen1,2, Ferdia A. Gallagher2,4, Kevin M. Brindle1,2

1Dept. of Biochemistry, University of Cambridge, Cambridge, UK; 2Cancer Research UK Cambridge Research Institute, Cambridge, UK; 3Dept. of Chemistry I.F.M, University of Turin, Italy; 4Dept. of Radiology, Addenbrooke’s Hospital, University of Cambridge, Cambridge, UK

In the current study, we compared the flux of hyperpolarized 13C pyruvate to lactate to markers of cell death in drug-resistant MCF-7 human breast cancer cells following treatment with a range of therapeutic agents. The results show that a decrease in pyruvate - lactate exchange coincides with the induction of cell death in breast cancer cells in vitro, with a decrease in exchange not observed in cells that fail to respond to treatment.

                  2421.     Hyperpolarized 13C MRS Detection of Reduced Pyruvate-Lactate Conversion Following PI3K Inhibition

Christopher S. Ward1, Humsa Venkatesh1, Alissa Brandes1, Mark van Criekinge1, Hagit Dafni1, John Kurhanewicz1, C. David James2, Daphne A. Haas-Kogan2, Sabrina M. Ronen1

1Radiology and Biomedical Imaging, UCSF, San Francisco, CA, USA; 2Neurological Surgery, UCSF, San Francisco, CA, USA

This study demonstrates the efficacy of hyperpolarized 13C MRS as a method to detect target modulation following PI3K inhibitor treatment in MDA-MB-231 breast adenocarcinoma and glioma neurosphere cells. 13C MR spectra revealed that treatment with 50 µM LY294002 for 40 hr reduced conversion of hyperpolarized pyruvate to lactate to 70±16% of control in MDA-MB-231 and 45±14% in GBM. LDH activity assay and Western blotting confirmed this effect to be the result of reduced lactate dehydrogenase levels following PI3K inhibition. This work suggests promising applications for hyperpolarized 13C MR as a noninvasive method to monitor responses to targeted anticancer treatments.

                  2422.     Spin Tagging in Hyperpolarzied Carbon-13 Metabolic Studies

Charles H. Cunningham1,2, Albert P. Chen3, Ralph E. Hurd4

1Dept. of Medical Biophysics, University of Toronto, Toronto, ON, Canada; 2Imaging Research, Sunnybrook Health Sciences Centre, Toronto, ON, Canada; 3GE Healthcare, Toronto, ON, Canada; 4GE Healthcare, Menlo Park, CA, USA

The biochemical reactions observed in hyperpolarized 13C studies are presumed to occur within the cellular cytosol and organelles, so it is therefore reasonable to assume that the measured carbon-13 signals contain a large intracellular component. The hypothesis of this study was that sinusoidal tagging of the longitudinal magnetization could be used to differentiate metabolic products in the intracelluar space from those flowing in the blood pool. All metabolites were observed to decay rapidly following the application of the spatial tags, suggesting that although the biochemical reactions occur within the cytosol, the resulting metabolic products are quickly transported out of cells.

                  2423.     Radiation Damping Observed in Hyperpolarized 13C-1-Pyruvate at 14.1 T

Mark VanCriekinge1, Albert Chen2, Dan Vigneron1, James Tropp3

1Radiology, UCSF, San Francisco, CA, USA; 2Applied Science Laboratory, GE Healthcare, Toronto, Ontario, Canada; 3Applied Science Laboratory, GE Healthcare, Femont, CA, USA

We present measurements showing the unambiguous presence of radiation damping in hyperpolarized [1-13C] Pyruvate, measured in vitro at a static field strength of 14.1 T.

                  2424.     Multi-Coil Metabolic Imaging, with SENSE Reconstruction, of  Hyperpolarized [1-13C] Pyruvate in a Live Rat at 3.0 T

James Tropp1, Albert Chen2, Janine Lupo3, Paul Calderon4, Thomas Grafendorfer5, Don McCune6, Fraser Robb6, Yi-Fen Yen7, Peder Larson3, Robert Bok3, Simon Hu3, Rolf Schulte8, Dan Vigneron3, Ralph Hurd7, Sarah Nelson3

1Applied Science Laboratory, GE Healthcare, Femont, CA, USA; 2Applied Science Laboratory, GE Healthcare, Toronto, Ontario, Canada; 3Radiology, UCSF, San Francisco, CA, USA; 4Engineering, GE Healthcare, Femont, CA, USA; 5Engineering, GE Healthcare, Menlo Park, CA, USA; 6Engineering, GE Healthcare, Aurora, OH, USA; 7Applied Science Laboratory, GE Healthcare, Menlo Park, CA, USA; 8MR, GE Healthcare, Garching bei Muenchen, Germany

We present multi-channel metabolic images of of hyperpolarized [1-13C] Pyruvate in the live rat, with full k space and reduced field of view acquisition with SENSE reconstruction, showing good correlation with anatomic (proton) images taken in the same exam, without moving the animal.

                  2425.     Comparison of HMQC and Dynamic Nuclear Polarization for Detection of 13C Tracers in the Perfused Mouse Heart

Crystal Harrison1,2, A Dean Sherry3,4, Craig R. Malloy5,6, Matthew E. Merritt7,8

1Physics, University of Texas at Dallas, Richardson, TX, USA; 2AIRC, UTSW, Dallas, TX, USA; 3AIRC, UTSW Medical Center, Dallas, TX, USA; 4Chemistry, University of Texas at Dallas, Richardson, TX, USA; 5AIRC, AIRC, Dallas, TX, USA; 6Cardiology, North Texas VA Hospital, Dallas, TX, USA; 7Advance Imaging Research Center, UT Southwestern Med. Center, Dallas, TX, USA; 8Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA

The proliferation of mouse models of human pathologies has driven a need for increased sensitivity in MRS. Proton detection of [3-13C]pyruvate is compared to direct detection of hyperpolarized [1-13C]pyruvate in the perfused mouse heart. HMQC does not suffer from loss of polariation due to T1, but lacks the ability to measure oxidative metabolism.

                  2426.     On the Perfomance of RARE, TRAPS and BSSFP in Imaging of Hyperpolarized Compounds

Jochen Leupold1

1Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany

Three slice-selective fast imaging sequences, namely RARE, TRAPS and balanced SSFP are investigated based on simulations for imaging of hyperpolarized nuclei. The signal outcome and artefact behaviour after intergation of the bloch equation is compared and evaluated.

                  2427.     Effect of Albumin on Longitudinal Relaxation of [1-13C1]-Pyruvate

Karlos X. Moreno1, Scott Sabelhaus1, Craig R. Malloy1, A Dean Sherry1, Matthew E. Merritt1

1Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, Tx, USA

Pyruvate binds to albumin. In the absence of albumin, the metabolic products of 2 mM hyperpolarized-[1-13C1]-pyruvate (HP-Pyr) are easily detected in the isolated heart but much higher [pyruvate] is required in the presence of albumin. The T1 of [1-13C1]-pyruvate is significantly reduced in the presence of albumin containing fatty acids and even more prominent in the presence of fatty acid-free albumin. Albumin catalyzes the relatively slow exchange of pyruvate methyl protons with solvent protons, suggesting transient covalent binding to albumin. The kinetics of these complex pyruvate/albumin interactions may play a significant role in hyperpolarized 13C imaging in vivo.

                  2428.     Secondary Substrate Assisted Dynamic Nuclear Polarization

Albert P. Chen1, Charles H. Cunningham2, David M. Wilson3, Susan J. Kohler4, John Kurhanewicz3, Daniel B. Vigneron3, Ralph E. Hurd5

1GE Healthcare, Toronto, ON, Canada; 2Sunnybrook Health sciences centre, Toronto, ON, Canada; 3Radiology, UCSF, San Francisco, CA, USA; 4Union College, Schenectady, NY, USA; 5GE Healthcare, Menlo Park, CA, USA

To achieve high polarization enhancement in a short time, MR probes polarized via DNP have been limited to substrates with low molecular weight and high solubility in organic solvent/water. But it may be possible to enhance the polarization of a target substrate that has poor DNP properties (low solubility, poor enhancement) with a secondary substrate that demonstrates high DNP enhancement and can be added in high concentration, allowing the secondary nuclei to assist the polarization of the target nuclei via spin diffusion. This technique was tested in this study with 13C urea as the secondary substrate.

                  2429.     Localized Spectroscopy in the Rat Brain Following Hyperpolarized [2-13C]pyruvate Injection

Isabelle Iltis1, Dinesh Kumar Deelchand1, Christopher Nelson1, Pierre-Gilles Henry1, Malgorzata Marjanska1

1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA

In this work, we measured hyperpolarized 13C signals in the rat brain in vivo following i.v. injection of hyperpolarized [2-13C]pyruvate in fasted and non-fasted animals. Time courses were obtained for resonances from [2-13C]pyruvate, [2-13C]pyruvate hydrate and [2-13C]lactate. Using LASER, we observed in the brain a resonance at 182.8 ppm only when the animals were fasted. This suggests that [2-13C]-pyruvate is metabolized in the liver and one of its byproducts is transported to the brain.

                  2430.     Imaging Carbonic Anhydrase Activity Using Hyperpolarized 13C-Labeled Bicarbonate

Ferdia Aidan Gallagher1,2, Mikko I. Kettunen2,3, Rebekah L. McLaughlin2,3, De-en Hu2,3, Tim H. Witney2,3, Jan H. Ardenkjaer-Larsen4, Kevin M. Brindle2,3

1Radiology, University of Cambridge, Cambridge, UK; 2CRUK Cambridge Research Institute, Cambridge, UK; 3Biochemistry, University of Cambridge, Cambridge, UK; 4GE Healthcare, Amersham, UK

Carbonic anhydrase (CA) is of biological importance because tumor-associated CAs (e.g. CA IX) have been shown to be strongly induced by hypoxia and controlled by hypoxia-inducible factor-1 (HIF-1). Therefore imaging CA may directly relate to hypoxia and HIF-1 activation. We show here that CA activity can he imaged both in vitro and in vivo following the injection of hyperpolarized 13C-labeled bicarbonate by saturating the 13C-labeled carbon dioxide. This represents a new application of Dynamic Nuclear Polarization.

                  2431.     Examination of Mouse Mammary Tumor Cell Metabolism with Hyperpolarized [1-13C] Pyruvate in the Presnce and Absence of Glutamine

Anthon Mancuso1, Stephen Kadlecek2, Robert V. Cadman2, Matthew A. Stetz2, Roland Knoblauch1, Craig B. Thompson, Rahim Rizi2

1Cancer Biology, University of Pennsylvania, Philadelphia, PA, USA; 2Radiology, University of Pennsylvania, Philadelphia, PA, USA

Glutamine is a critical metabolite for the rapid growth of many cancer cell types. We examined the metabolism of hyperpolarized [1-13C]pyruvate in mouse mammary tumor cells in culture medium with and without glutamine. Lactate was the predominant end product and very little labeled alanine was observed, which was surprising since normally these cells produce significant amounts of alanine from glucose. Another interesting finding was that lactate was reduced when pyruvate plus NH4Cl was substituted for glutamine suggesting that omitting glutamine was not compensated for with increased flux through lactate dehydrogenase (and presumably glycolysis). Lastly, no metabolites were observed that would suggest pyruvate carboxylase is active. Thus, the primary effect of omitting glutamine from the medium would appear to be an overall reduction in metabolic activity.

                  2432.     Kinetic Modeling of Hyperpolaized [1-13C]Pyruvate Metabolism in Blood

Kevin Kai-Chi Leung1,2, Wilfred W. Lam1, Albert P. Chen3, Charles H. Cunningham1,2

1Imaging Research, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; 2Dept. of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada; 3GE Healthcare, Toronto, Ontario, Canada

In tumor metabolic studies that use hyperpolarized carbon-13 compounds and MR spectroscopy, there are metabolic products generated elsewhere in the body that enter the tissue of interest via the blood stream and complicate the analysis of local metabolism. This study attempted to quantify pyruvate-lactate conversions in ex vivo whole blood that might be useful in estimating blood metabolic contribution to regions of interest in in vivo studies. We showed that there is great variability in metabolic conversion rates among subjects and that metabolism in blood is very small compared to rat kidney tissues.

                  2433.     Efficient Hyperpolarised 13C Metabolic Imaging with Rosette Spectroscopic Imaging

Rolf F. Schulte1, Florian Wiesinger1, Kenneth M. Fish2, David Whitt2, Ileana Hancu2

1GE Global Research, Munich, Germany; 2GE Global Research, Niskayuna, NY, USA

Metabolic imaging with hyperpolarised 13C compounds requires rapid spectral and spatial

                  2434.     Hyperpolarized 13C MRS in the Rat Brain: Spatial Origin of Signals

Malgorzata Marjanska1, Isabelle Iltis1, Dinesh K. Deelchand1, Michael Garwood1, Pierre-Gilles Henry1

1Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minneapolis, MN, USA

The low sensitivity of 13C spectroscopy can be enhanced using dynamic nuclear polarization (DNP) technique. Detection of [1-13C]pyruvate and its metabolic products have been reported in kidney, liver, muscle, and brain. In this work, we investigate the spatial origin of [1-13C]pyruvate and [1-13C]lactate signals in rat brain.

                  2435.     Feasibility of SNR Enhancement in Flyback Echo Planar Spectroscopic Imaging Through Parallel Imaging with Application to Hyperpolarized 13C Metabolic Imaging

Cornelius von Morze1, Peder EZ Larson1, Simon Hu1, Adam B. Kerr2, Michael Lustig2, James Tropp3, John M. Pauly2, Daniel B. Vigneron1

1Department of Radiology and Biomedical Imaging, UCSF, San Francisco, CA, USA; 2MRSRL, Department of Electrical Engineering, Stanford University, Stanford, CA, USA; 3GE Healthcare, Fremont, CA, USA

An implementation of GRAPPA parallel imaging for improved SNR efficiency in flyback echo planar spectroscopic imaging is proposed and evaluated, for application to hyperpolarized 13C-1 pyruvate imaging. We investigate a combination of a faster approach to phase encoding through parallel imaging with a slower approach to the echo planar readouts, for a net improvement in SNR efficiency. The expected 40% SNR gain for the slower readouts in this application was found to outweigh estimated reconstruction-related errors and SNR losses, showing good potential for this technique.

                  2436.     Autotriggering for DNP-Polarized In-Vivo 13C Experiments

Venkat Ramanan1, Albert Pofu Chen2, Graham A. Wright1, Charles H. Cunningham1

1Imaging Research, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; 2GE Healthcare, Toronto, Ontario, Canada

Hyperpolarized 13C labeled pyruvate has been used to study metabolic processes in-vivo. In these applications, it is useful to know the transit time taken for the contrast to travel from injection site to the imaging area of interest. This is then used to start an imaging sequence such as CSI at a specific time most suited for the desired contrast. Usually a dynamic non-localized FID experiment is done to get an estimate of the transit time. Here we present a method to gather and plot

                  2437.     Measuring Glutamate Metabolism in Vivo in Tumors Using Dynamic Nuclear Polarization

Ferdia Aidan Gallagher1,2, Mikko I. Kettunen2,3, De-en Hu2,3, Sam E. Day2,3, Magnus Karlsson4, Anna Gisselsson4, Mathilde H. Lerche4, Kevin M. Brindle2,3

1Radiology, University of Cambridge, Cambridge, UK; 2CRUK Cambridge Research Institute, Cambridge, UK; 3Biochemistry, University of Cambridge, Cambridge, UK; 4Imagnia AB, Malmö, Sweden

The number of metabolites that can be hyperpolarized using Dynamic Nuclear Polarization is increasing. Here we show that [1-13C]glutamic acid can also be polarized. The metabolism of hyperpolarized glutamate to á-ketoglutarate, catalyzed by the enzyme alanine transaminase, was detected in vitro and in vivo in tumor models. As non-polarized á-ketoglutarate is below the threshold for MRS detection, this presents a new method for probing tumor metabolism.

                  2438.     A Large Volume Multi-Samples DNP Polarizer Dedicated to MR Biomedical Applications

Florent Goutailler1, Bruno Montcel1, Gérard Vermeulen2, Dominique Grand2, Pierre-Etienne Wolf2, Yannick Cremillieux1

1Creatis-LRMN Lab., University of Lyon, Lyon, France; 2Neel Institute, University of Grenoble, Grenoble, France

This work presents a large volume multi-samples DNP polarizer. The specifications of the magnet and the design of the different systems (cryogenic, millimeter waves and dissolution) have been optimized for producing one or several batches of contrast solutions with a high polarization, in a short time lap. This system opens up the way to new promising biomedical applications.

                  2439.     13C- & 31P-Hyperpolarized Intermediates of Glucolysis and Gluconeogenesis: Phosphoenolpyruvate

Joachim Bargon1, Rahim R. Rizi2

1Institute of Physical Chemistry, University of Bonn, Bonn, Germany; 2Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, PA, USA

Phosphoenolpyruvate (PEP) represents a high-energy intermediate in both glucolysis and gluconeogenesis. This enol phosphate has a high phosphoryl-transfer potential. Therefore, hyperpolarizing PEP via ParaHydrogen Induced Polarization (PHIP) provides access to both 13C-hyperpolarized pyruvate and 31P-hyperpolarized ATP. From the latter the 31P-hyperpolarization can be transferred to other molecules that need ATP for their formation. Due to efficient relaxation, only very fast conversions qualify for this purpose. Even the PEP itself qualifies as an unsaturated precursor for parahydrogenation, but then the driving force for the phosphoryl-transfer is reduced. In plants, PEP is a precursor for the biosynthesis of the aromatic amino acids.

                  2440.     Validation of an Efficient and Compact Para-Hydrogen Catalytic Converter System for PHIP Studies

Ayelet Gamliel1,2, Hyla Allouche-Arnon1,3, Ruppen Nalbandian1,3, Elena Vinogradov4, Aaron K. Grant4, Robert E. Lenkinski4, Claudia M. Barzilay2, J. M. Gomori1, Rachel Katz-Brull1

1Department of Radiology, Hadassah Hebrew University Medical Center, Jerusalem, Israel; 2Medicinal Chemistry, School of Pharmacy , The Hebrew University of Jerusalem, Jerusalem, Israel; 3Department of Physiology, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel; 4Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA

An efficient and compact para-hydrogen catalytic converter system for PHIP studies is described. The system consists of local production of small predetermined amounts of hydrogen and an efficient and convenient catalytic converter at ambient pressure. In this system, the enhancement factor per concentration was c.a. 2,100 and c.a.3,500 for 1H- and 13C- ALTADENA studies, respectively. The system proved to be an excellent source of para-hydrogen for PHIP studies in a hospital/MRI suite environment.

                  2441.     Hyperpolarization Storage at Different Magnetic Field on Perdeuterated Parahydrogenated Molecules for MRI Application

Francesca Reineri1, Daniela Santelia1, Roberto Gobetto1, Silvio Aime1

1Chemistry I.F.M., University of Turin, Torino, Italy

The application of hyperpolarized molecules as MRI contrast agents is gathering increasing attention. Two methods are used to achieve hyperpolarization, namely DNP and ParaHydrogen Induced Polarization. The application of both is strongly limited by polarization decay rate, that shortens polarization lifetime to some tens of seconds. In order to keep polarization on parahydrogenated molecules both substrate deuteration and singlet state maintenance on product molecule have been applied. A molecule is reported in which the application these two methods allows to achieve an exceptionally long T1, that make this molecule particularly interesting for in vivo MRI.

                  2442.     Effects of Deuteration on 13C Relaxation Times in Neuro-Metabolic Compounds: Implications for Hyperpolarized Spectroscopic Imaging

Hyla Allouche-Arnon1,2, Ayelet Gamliel3,4, Ruppen Nalbandian3,5, Mor Mishkovsky6, Lucio Frydman6, J. Moshe Gomori3, Robert E. Lenkinski7, Claudia M. Barzilay4, Rachel Katz-Brull3

1Department of Radiology, Hadassah Hebrew University Medical Center , Jerusalem, Israel; 2Department of Physiology, The Hebrew University of Jerusalem, Jerusalem, Israel; 3Department of Radiology, Hadassah Hebrew University Medical Center, Jerusalem, Israel; 4Medicinal Chemistry- School of Pharmacy, The Hebrew University of Jerusalem, Jerusalem, Israel; 5Department of Physiology, The Hebrew University of Jerusalem,, Jerusalem, Israel; 6Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel; 7Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA

Hyperpolarization,obtained either by PHIP or DNP may result in 10,000 fold enhancement of the NMR signal. However, its utilization is limited by the decay of the polarization from the moment of its generation due to T1. Enrichment of proton positions with Deuterium nuclei is known to prolong the T1 of an adjacent spin ½ in a manner that is critically dependent on the conformation taken by the molecule in solution. In this work we report on the deuteration related T1 elongation effect in two neuro-metabolic compounds, namely choline and dopamine, which may have diagnostic potential for neurodegenerative diseases.

                  2443.     In Vivo Hyperpolarized Lipophilic Agents Targeting Atherosclerotic Plaque

Eduard Y. Chekmenev1, Henry Chan1, Shawn R. Wagner1, Wanda F. Reynolds2, Brian D. Ross1, Pratip Bhattacharya1

1Enhanced MR Unit, Huntington Medical Research Institutes, Pasadena, CA, USA; 2Sidney Kimmel Cancer Center, San Diego, CA, USA

We report on the novel in vivo application of 13C hyperpolarized agents to target atherosclerotic plaque. We demonstrate that 13C hyperpolarized tetrafluoropropyl propionate (TFPP) interacts with excess lipid in genetically engineered low-density lipoprotein deficient mice by detecting a lipid specific MR resonance 3 ppm away from the main solution peak. Moreover, in vivo 13C spectroscopy of hyperpolarized TFPP and ex vivo 19F spectroscopy provide evidence that this technique is capable of differentiating lipid content in low-density lipoprotein deficient and control mice. Additional work is in progress in our laboratory to provide statistically relevant results.

                  2444.     Cancer Imaging with Succinate Hyperpolarization

Pratip Bhattacharya1, Eduard Y. Chekmenev1, Shawn Wagner1, Henry R. Chan1, William H. Perman2, Alan Epstein3, Brian D. Ross4

1Enhanced MR Laboratory, Huntington Medical Research Institutes, Pasadena, CA, USA; 2School of Medicine, St. Louis University, St. Louis, MO, USA; 3Department of Pathology, University of Southern California, Los Angeles, CA, USA; 4Enhanced MR Laboratory, Huntington Medical Research Institutes, Pasadena, Pasadena, CA, USA

Succinate can be now be hyperpolarized at over 20% level of polarization routinely and reproducibly in our laboratory. Succinate is biomedically interesting as it can potentially assess the in vivo activity of succinate dehydrogenase (SDH), the enzyme that was recently tagged as an oncogene due to its crucial role in cell energetics. This abstract describes the application of hyperpolarized succinate for imaging cancer in different tumor models in mice.

                  2445.     Flip Angle Calibration Using SPAMM for Hyperpolarized 3He MRI

Julien Rivoire1, Maxim Terekhov2, Elena Knaub2, Florian M. Meise2, Sergei Karpuk3, Wolfgang G. Schreiber2

1Section of Medical Physics, Department of Radiology,, Mainz University Medical School, Mainz, Germany; 2Section of Medical Physics, Department of Radiology, Mainz University Medical School, Mainz, Germany; 3Institute of Physics, Johannes Gutenberg University, Mainz, Germany

In hyperpolarized 3He MRI, a flip angle calibration is necessary especially in case of using no-tune coils. A new calibration method based on the analysis of the phase image following a Spatial Modulation of Magnetization preparation (SPAMM) is presented in this work. It has the advantage of being free of error due to the T1 relaxation decay cause by oxygen and does not require image processing with external software but uses the standard commercial scanner interface tool and a simple calculator.

                  2446.     Increased Volumetric Activity for Hyperpolarized DNP Solutions

Eric T. Peterson1, Matthew G. Erickson2, Sean B. Fain2, Ian J. Rowland3

1Biomedical Engineering, University of Wisconsin - Madison, Madison, WI, USA; 2Medical Physics, University of Wisconsin - Madison, Madison, WI, USA; 3Radiology, University of Wisconsin - Madison, Madison, WI, USA

This work presents a method for concentrating a hyperpolarized compound prior to injection. By replacing 75% of the water in a typical dissolution with a chemically and biologically inert liquid that is immiscible with water, the injected volume can be readily reduced to approximately 1.5 ml. This provides a more concentrated solution shortening injection time for an equivalent dose while flushing a sufficient volume of fluid through the system. This is demonstrated for 13C labeled pyruvic acid, but may be applied to any compound hyperpolarized by the DNP method.

                  2447.     Real Time Liquid State Polarization Measurements for in Vivo Exams Using Hyperpolarized 13C Compounds

Ileana Hancu1, Randy Giaquinto1, Robert Lenkinski2, W Thomas Dixon1

1GE Global Research Center, Niskayuna, NY, USA; 2Beth Israel Deaconess Medical Center, Boston, MA, USA

A hardware setup to allow real-time liquid state polarization (LSP) measurements from hyperpolarized compounds in the MRI magnet is presented. Three miniature transmit/receive Helmholtz coils, rigidly fixed to each other, are designed to surround the patient injection tube and create mutually orthogonal fields. The sensitivity of this setup in measuring signals from small 13C enriched samples (to constitute the reference for the hyperpolarization measurements) is demonstrated. The relative orientational invariance of the signal measurements is also shown, confirming that such a setup can achieve accurate LSP measurements.

                  2448.     No Clinical Toxicity Is Seen in Vivo from Hyperpolarized PASADENA MR Reagents or Catalyst

Henry R. Chan1,2, Pratip Bhattacharya1, Ashraf Imam1, Anna Freundlich1, Thao Tran2, William H. Perman3, Alexander P. Lin1, Kent Harris1, Eduard Y. Chekmenev1, Marylou Ingram1, Brian D. Ross1

1Enhanced Magnetic Resonance Laboratory, Huntington Medical Research Institutes, Pasadena, CA, USA; 2Rudi Schulte Research Institutes, Santa Barbara, CA, USA; 3Department of Radiology, St. Louis University, St. Louis, MO, USA

Hyperpolarized 13C-enriched compounds can provide enough signal for magnetic resonance spectroscopy to potentially trace the metabolic processes of living cells, in situ. Preparatory to any clinical study, the safety profile of candidate tracer reagents and reaction catalysts must be characterized. We report that the rhodium norbordiene catalyst, critical to the PASADENA method of hyperpolarization, produces no clinical signs of disease in rats despite inhibiting growth in liver cell cultures. Intravenous succinate was also well tolerated up to a 300 mM (151.7 mg/kg) dose, well above the usual 10-30 mM imaging dose.

                  2449.     Development of a Fast Field-Cycling Method for Polarizing C13 Using Parahydrogen-Induced Polarization

Aaron K. Grant1, Elena Vinogradov1

1Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA

In parahydrogen-induced polarization (PHIP), carbon-13 polarization is usually obtained using field cycling techniques or RF pulse sequences. Field cycling techniques are simple but relatively slow, whereas RF pulse techniques are faster but require more sophisticated hardware. Here we present studies of a simple field cycling method that employs a modified time-dependent field pattern to achieve high levels of polarization in a short time. We present theoretical computations to show that the method should be capable of yielding high polarization levels in a few tens of milliseconds, and preliminary data that qualitatively support the theoretical expectations.

                  2450.     Hyperpolarized 1H NMR Employing Low Gamma Nucleus as a Spin Order Storage

Eduard Y. Chekmenev1,2, Valerie A. Norton2, Pratip Bhattacharya1, Brian D. Ross1, Daniel P. Weitekamp2

1MRS, Huntington Medical Research Institutes, Pasadena, CA, USA; 2California Institute of Technology, Pasadena, CA, USA

We show the utility of low-gamma nuclei, for example 13C, for spin storage of hyperpolarization followed by 1H detection, which theoretically can provide up to ~(γ1HX) 2 gain in sensitivity in hyperpolarized biomedical MR compared to direct detection of hyperpolarized low-gamma nuclei such as 13C, 15N, etc. This concept is demonstrated for biologically relevant reagents: 13C hyperpolarized succinate and tetrafluoropropyl propionate. Theoretical analysis and experimental results using refocused INEPT provide evidence that spin order transfer efficiency from 13C to 1H is in excess of 50%.

                  2451.     Hyperpolarized 15N MR: PASADE15NA & D15NP

Pratip Bhattacharya1, Shawn Wagner1, Henry R. Chan1, Eduard Y. Chekmenev1, William H. Perman2, Brian D. Ross3

1Enhanced MR Laboratory, Huntington Medical Research Institutes, Pasadena, CA, USA; 2School of Medicine, St. Louis University, St. Louis, MO, USA; 3Enhanced MR Laboratory, Huntington Medical Research Institutes, Pasadena, Pasadena, CA, USA

Several significant biological and biomedical questions have been addressed by use of 15N MR. However, structural 15N NMR is hampered by the need for complex chemical substitutions and 15N enriched biomedical applications which are time consuming, limited by enzyme flux measurements of mmoles over seconds to minutes. Hyperpolarization of 15N by Parahydrogen And Synthesis Allows Dramatically Enhanced Nuclear Alignment (PASADENA) and Dynamic Nuclear Polarization (DNP) was explored as a means of broadening the biomedical utility of 15N MR imaging and spectroscopy. This abstract describes the hyperpolarization of several 15N molecules with both PASADENA and DNP techniques and their potential in vivo applications.

                  2452.     Towards Receptor Targeted 13C Hyperpolarized MR Contrast Agents

Eduard Y. Chekmenev1,2, Siu-Kei Chow1, Jan B. Hoevener1, Valerie A. Norton2, Kent C. Harris1, Thao T. Tran1, William H. Perman3, Daniel P. Weitekamp2, Brian D. Ross1, Pratip Bhattacharya1

1MRS, Huntington Medical Research Institutes, Pasadena, CA, USA; 2California Institute of Technology, Pasadena, CA, USA; 3Radiology, Saint Louis University, Saint Louis, MO, USA

We report the NMR of hyperpolarized agents designed for chemically-specific interaction with receptor sites.. We demonstrate that C-13 hyperpolarized tetrafluoropropyl propionate (TFPP) binds to synthetic lipid bilayers inducing an additional MR resonance which is shifted by 3 ppm and is in slow exchange with the main resonance. We find that this signature of TFPP is specific for lipids but not for albumin – the most abundant lipophilic serum protein. Moreover, 13C longitudinal spin relaxation under conditions of binding/exchange is >14 seconds, which is sufficient for potential in vivo applications (work in progress in our laboratory).

                  2453.     Parahydrogen Induced Polarization of Barbituric Acid Derivatives. 13C Hyperpolarization Studies

Meike Roth1, Kerstin Münnemann1, Joachim Bargon2, Hans Wolfgang Spiess1, Achim Koch1

1Max Planck Institute for Polymer Research, Mainz, Germany; 2Institute of Physical and Theoretical Chemistry, University of Bonn, Germany

NMR signal enhancement by PHIP techniques is interesting for spectroscopic investigations and may also find applications in MRI, which is of great importance for medical diagnostics. Hence, the role of certain target compounds such as anesthetics could be investigated by using MRI techniques. Among the drugs used to treat epilepsy or for injection narcotics, barbiturates like 5-methyl-5-propargylbarbituric acid are attractive from the medical and chemical point of view. By combining the PH-INEPT+ sequence with a “PASADENA experiment under pressure” of unsaturated barbituric acid derivatives a transfer of polarization to 13C was implemented yielding a dramatic signal increase of up to 1000.

                  2454.     13C NMR Signal Enhancement by Using Parahydrogen Induced Polarization (PHIP) and Appropriate Pulse Sequences

Meike Roth1, Joachim Bargon2, Hans Wolfgang Spiess1, Achim Koch1, Kerstin Münnemann1

1Max Planck Institute for Polymer Research, Mainz, Germany; 2Institute of Physical and Theoretical Chemistry, University of Bonn, Germany

Parahydrogen induced polarization (PHIP) has turned out to be a versatile technique to obtain hyperpolarized molecules exhibiting

                  2455.     Obstacles to Diagnostic PASADENA Hyperpolarization in Humans

Thao T. Tran1,2, Henry R. Chan1,2, Johnathan Chou1, Shawn Wagner1, Pratip Bhattacharya1,2, Brian D. Ross1,2

1Enhanced Magnetic Resonance, Huntington Medical Research Institutes, Pasadena, CA, USA; 2Rudi Schulte Research Institute, Santa Barbara, CA, USA

Magnetic resonance imaging and spectroscopy using hyperpolarized reagents has myriad applications to

                  2456.     Continuous Flow Dynamic Nuclear Polarization of Water Under Ambient Conditions for in-Vivo Perfusion MRI

Mark D. Lingwood1, Samuel T. Tokuyama2, Elliott R. Brown3, Songi Han1

1Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA; 2Pacifica Hosiptal of the Valley, Sun Valley, CA, USA; 3Department of Electrical and Computer Engineering, University of California, Santa Barbara, CA, USA

We are developing instruments and methods for in-vivo magnetic resonance imaging (MRI) using hyperpolarized water that is prepared by continuous-flow Overhauser dynamic nuclear polarization (DNP) under ambient conditions. Our compact and portable 0.35T DNP setup can be implemented in the fringe field any MRI system, and produces radical-free hyperpolarized water with 1H enhancements of up to -40 fold. In contrast to the dissolution DNP approach, where samples are polarized for hours at 1.2K, our method can continuously generate DNP-enhanced water under ambient conditions. We present our progress in developing the specialized equipment for this procedure and display our initial results.

                  2457.     Dynamic Nuclear Polarization of Silicon-Based Nanoparticle Magnetic Resonance Imaging Agents

Maja Clare Cassidy1, Jacob W. Aptekar2, Menyoung Lee2, Ronald L. Walsworth2,3, Charles M. Marcus2

1School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA; 2Department of Physics, Harvard University, Cambridge, MA, USA; 3Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA

Silicon based nanoparticles offer promise as biologically targeted magnetic resonance imaging (MRI) agents based on their exceptional NMR properties, receptivity to hyperpolarization, and diverse functionalization chemistry. Specifically, the long room temperature nuclear relaxation (T1) times of crystalline silicon nanoparticles makes them suitable candidates as ex-vivo polarized imaging agents. We present results on low temperature dynamic nuclear polarization of silicon and silicon-based nanoparticles of a variety of sizes, morphologies and fabrication methods. We will also discuss requirements for transporting pre-polarized particles, and mechanisms for imaging the hyperpolarized nanoparticles in-vivo.

                  2458.     Long-T1 Silicon Nanoparticles for Hyperpolarized Magnetic Resonance Imaging

Maja Clare Cassidy1, Jacob Webster Aptekar1, Alexander C. Johnson1, Robert A. Barton1, Menyoung Lee1, Chinh Vo1, Alison L. Hill2, Ross Webster Mair2, Matthew S. Rosen1,2, Ronald L. Walsworth1,2, Charles M. Marcus1

1Department of Physics, Harvard University, Cambridge, MA, USA; 2Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA

Nanoparticles are currently being widely investigated as targetable contrast agents for magnetic resonance imaging (MRI). For these applications, the action of the nanoparticle is to alter the nuclear relaxation properties, as in traditional (untargeted) contrast agents. An alternative imaging modality is to use MRI to image the particles directly, without a background signal. Bulk silicon exhibits multi-hour nuclear relaxation T1 times at room temperature and can be hyperpolarized via dynamic nuclear polarization. Here we demonstrate the production and functionalization of silicon nanoparticles for use as hyperpolarized targeted imaging agents. The NMR properties are studied as a function of nanoparticle size, dopant concentration and synthesis method. Nuclear T1 times are found to be remarkably long, allowing for hyperpolarized particles to be transported and administered on practical time scales without significant polarization loss.

                  2459.     Simultaneous Imaging of Tumor Oxygenation and Microvascular Permeability Using Hyperpolarized 1H-MRI in Mice

Shingo Matsumoto1, Sonny Batra1, Hironobu Yasui1, Sankaran Subramanian1, Nallathamby Devasahayam1, Jeeva P. Munasinghe2, James B. Mitchell1, Murali C. Krishna1

1Radiation Biology Branch, National Cancer Institute, Bethesda, MD, USA; 2National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA

Angiogenesis is essential for solid tumors to grow beyond 1-2 mm3 and to switch from local vascular supply to novel microcapillary formation. During physiological angiogenesis, new vessels mature and become stable. However, in cancer, neovasculature is architecturally and functionally abnormal with large pores causing leakage of larger molecules. Increase in tumor microvascular permeability results in aberrant blood flow and regional hypoxia. Hypoxic tumors exhibit resistance to radiation therapy and so poor treatment outcome. In the present study, a novel technique for simultaneous imaging of tumor oxygenation and microvascular permeability using in vivo hyperpolarized 1H-MRI, known as Overhauser MRI (OMRI).

                  2460.     19F-MRI Using Hyperpolarized Substrates Generated Via Parahydrogen-Transfer

Ute Bommerich1, Samir Mulla-Osman2, Joachim Bargon3, Johannes Bernarding2

1Leibniz Institute for Neurobiology, Magdeburg, Germany; 2IBMI, University of Magdeburg, Magdeburg, Germany; 3Institute for Physical Chemistry, University of Bonn, Bonn, Germany

19F-MRI and -MRS are emerging methods with promising applications in medicine as highly interesting diagnostic tools. 19F nuclei do not appear in soft tissue, accordingly appropriate reporter molecules must be administered to perform correspondent investigations. As for all MR investigations this techniques suffer from an inherent low sensitivity so that an increase of signal to noise ratio for the related 19F-signals could boost the quality and quantity of possible applications. Hyperpolarization methods such as PHIP (ParaHydrogen Induced Polarization) are successfully applied for sensitivity enhancement and first 19F hyperpolarized substrates have been generated. In this contribution we present first 19F MR images which demonstrate the basic feasibility for an application of this method for MRI investigations.

                  2461.     Measurement of Hyperpolarized 15N-Choline Using Polarization Transfer with 1H Detection

Vladimir Denisov1,2, Arnaud Comment3,4, Paul Vasos5, Sami Jannin4, Jacques van der Klink4, Riddhiman Sarkar5, Geoffrey Bodenhausen5, Helene Hall1, Deniz Kirik1,2

1Department of Experimental Medical Science, Brain Repair and Imaging in Neural Systems, Lund University, Lund, Sweden; 2Lund University Bioimaging Center, Lund University, Lund, Sweden; 3Laboratory for Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; 4Laboratory for Physics of Nanostructured Materials, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; 5Laboratory for Biomolecular Magnetic Resonance, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

Choline is an important precursor of acetylcholine, betaine and phosphatidylcholine. Its metabolism, which represents an important biomarker in oncology, can be studied using hyperpolarized 15N MRS. Here we investigated possibility of the transfer of 15N-choline hyperpolarizarion from nitrogen to protons with subsequent 1H MRS detection. The results indicate that the polarization transfer methods can be used to utilize the long relaxation time of 15N-choline for the storage of nuclear hyperpolarization (thus allowing more time for the sample delivery, biodistribution and metabolic conversion), and subsequently obtain an improved spectral resolution of metabolites together with superior sensitivity, provided by the 1H detection.

                  2462.     Sub-Micromolar Concentrations of Contrast Agent Have a Quantifiable Influence on the Hyperpolarized Lithium-6 Relaxation Time in Vivo

Ruud Bernardus van Heeswijk1, Fiodar Kurdzesau2,3, Cristina Cudalbu1, Arnaud Comment1,2, Jacques J. van der Klink2, Gil Navon4, Rolf Gruetter1,5

1Center for BioMedical Imaging (CIBM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, VD, Switzerland; 2Laboratory for Physics of Nanostructured Materials, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, VD, Switzerland; 3Paul Scherrer Institute, Villigen, Switzerland; 4School of Chemistry, Tel Aviv University, Tel-Aviv, Israel; 5Departments of Radiology, Universities of Lausanne and Geneva, Switzerland

Lithium-6 has recently been demonstrated to have longitudinal decay times on the order of minutes and to be readily hyperpolarizable by dynamic nuclear polarization (DNP). It was also shown to be quite sensitive to the negatively charged contrast agent Gd-DOTP. The aim of this study was to demonstrate that these principles can be combined to quantitatively detect very low concentrations of contrast agent: the longer the relaxation time, the more sensitive it becomes to the contrast agent.

 
Non-Proton MRI
Exhibit Hall 2-3                    Monday 14:00-16:00

                  2463.     Optimal Choice of Pulse Phases in Triple-Quantum Filtered Sodium Imaging in the Presence of B0 Inhomogeneities

Christian Matthies1, Armin M. Nagel1, Lothar R. Schad2, Peter Bachert1

1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany; 2Chair in Computer Assisted Clinical Medicine, University of Heidelberg, Mannheim, Germany

For diagnostic purposes, in sodium (23Na) MRI, the discrimination between free sodium ions and sodium ions restricted in their mobility is desirable. One method to isolate the signal from such ions is triple-quantum filtered sodium MRI. However, a problem connected with this method is the pronounced sensitivity to inhomogeneities in the B0 field. To reduce the influence of the latter, pulse phases must be chosen carefully. We propose a fast method to find optimal values for the pulse phases before measurement and acquire triple-quantum filtered sodium images of the human head.

                  2464.     Evaluation of Lung Tumor Oxygenation Using FREDOM and TOLD

Jesus Pacheco-Torres1,2, Dawen Zhao2, Debu Saha2, Pilar Lopez-Larrubia3, Sebastian Cerdan3, Ralph P. Mason2

1Instituto de Investigaciones Biomédicas "Alberto Sols" - CSIC , Madrid, Spain; 2University of Texas Southwestern Medical Center, Dallas, TX, USA; 3Instituto de Investigaciones Biomédicas "Alberto Sols" - CSIC, Madrid, Spain

We investigate in this work the relationship between two techniques currently used for assessing tumor oxygenation: TOLD and FREDOM. The former is based in the shortening of tissue water T1 due to dissolved molecular oxygen and thus directly applicable to the clinic. FREDOM is a 19F MR based approach that uses hexafluorobenzene as the reporter molecule and offers quantitative pO2 values. This is the first time that these two approaches are studied in the same cohort of animals bearing A549 lung tumors. A direct correlation between pO2 during hyperoxic gas breathing and TOLD response to oxygen challenge was found.

                  2465.     Parameter Optimization for 7T 23Na-MRI

Armin Michael Nagel1, Sebastian Schmitter1, Michael Bock1, Ewald Moser2,3, Wolfhard Semmler1, Lothar Rudi Schad4

1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany; 2MR Centre of Excellence, Medical University of Vienna, Vienna, Austria; 3Institute for Biomedical Engineering and Physics, Medical University of Vienna, Vienna, Austria; 4Computer Assisted Clinical Medicine, Faculty of Medicine Mannheim, University Heidelberg, Mannheim, Germany

The purpose of this study is to provide parameters for the optimization of 23Na-MRI protocols at 7 T. Therefore, T1 and T2* relaxation times of the human brain and different phantoms were measured. SNR and image quality was investigated at three field strengths (1.5 T, 3 T, 7T). The theoretically expected approximately linear increase in SNR with field strength could be confirmed, with minor deviations that can be attributed to relaxation effects. Furthermore, it was shown that appropriate sequence designs, such as a density adapted radial sequence can reduce degradations of image quality due to B0-inhomogeneities even at 7 T.

                  2466.     Sodium ‘Invisibility’ in Single Quantum Sodium Imaging of the Human Brain

Rob Stobbe1, Christian Beaulieu1

1Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada

An altered signal intensity dependence on prescribed flip angle is demonstrated for sodium projection imaging of the human brain in white matter regions, especially those with tracts predominantly running parallel to the static magnetic field. Relative regional signal loss on `non relaxation weighted` sodium images acquired with 90o flip angles, as opposed to 53o flip angles, is proposed to result from residual quadrupole spectral splitting in the highly ordered white matter fibres on the order of or greater than the RF pulse bandwidth. The associated signal loss is important to consider for quantitative tissue sodium concentration mapping.

                  2467.     Fluorine-19 Based MR Imaging Tracer 19FIT for Drug Dilvery Research.

Xin Liu1, Zhong-Xing Jiang2, Yihua Bruce Yu2, Eun-Kee Jeong3

1Physics, University of Utah, Salt Lake City, UT, USA; 2Bioengineering, University of Maryland, College Park, MD, USA; 3Radiology, University of Utah, Salt Lake City, UT, USA

Fluorine-19 is a promising reporter for drug delivery research because of its high NMR sensitivity, 100% natural abundance and minimal background interference from human body. However, MR imaging of most fluorinated compounds suffers from low signal intensity caused by low quantity, long T1, and multiple chemical shifts, and low hydrophilicity causes long retention time which might increase the toxicity. To address these issues, we present a 19F based multifunctional drug delivery vehicle 19Fluorine Imaging Tracer (19FIT). Our 19FIT contains 27 19F nuclei in each molecule with identical chemical shift. Its relatively short T1 (253.3±25.0 ms in solution and ~370 ms in vivo at 3 T) of our compound allows for increased signal averages in unit scan time and its short retention time reduce the toxicity risk.

                  2468.     23Na SPRITE in Vivo Human Brain Tumour Imaging

Joachim B. Kaffanke1,2, Sandro B. Romanzetti1, N. Jon Shah1,2

1Institute of Neurosciences and Biophysics, Research Centre Juelich, Juelich, Germany; 2Faculty of Medicine, Department of Neurology, RWTH Aachen University,  JARA, Aachen, Germany

A SPRITE sequence was developed for sodium in vivo imaging applications. The sequence was extended by multiple point acquisition, conical k-space trajectory, repetition time and flip angle reduction to reduce acquisition time and SAR and a phase cycling filter for suppression of residual signal artefacts. The image reconstruction with the chirp z-transform was improved by use of an algorithm for resolution enhancement. The success of the method was demonstrated by imaging a human brain tumour. The sodium imaging results are compared with FET-PET and proton MR imaging.

                  2469.     Imaging an Inflammatory Response in a Sponge Granuloma Model Using 19F-MRI

Vinod Kaimal1, Tracey Monterosso1, Michael Woolliscroft1, Joseph Cornicelli1, Robbie B. Mailliard2, Eric T. Ahrens3, Aaron D. Nelson3, Cameron Barnard4, James Mobley5, Patrick McConville1

1MIR Preclinical Services, Ann Arbor, MI, USA; 2Celsense, Inc, Pittsburgh, PA; 3Celsense, Inc., Pittsburgh, PA, USA; 4m2m Imaging Corp., Cleveland, OH, USA; 5Lycera, Ann Arbor, MI, USA

An inflammatory response was induced in mice using PVA sponges that were soaked in either complete Freund’s adjuvant (CFA) or PBS (control) and implanted subcutaneously in the dorsal surface of Balb/C mice. A perfluorocarbon nanoparticle emulsion, injected intravenously, was used to detect the inflammatory response, using 19F-MRI . The types of cells involved in this response were identified using Fluorescence Activated Cell Sorting. Results suggest that the 19F based nanoemulsion is a specific in vivo biomarker for an activated macrophage subtype involved in the inflammatory response and can potentially be used to quantify macrophage activity.

                  2470.     Quantitative Sodium MRI of the Mouse Prostate

Jamie Near1,2, Robert Bartha1,2

1Centre for Functional and Metabolic Mapping, Robarts Research Institute, London, Ontario, Canada; 2Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada

A method is described for quantitative sodium MRI of the mouse prostate at 9.4 Tesla. A radiofrequency coil was constructed and dual-tuned to both the proton and sodium frequencies. High resolution (125x125x300 μm) T2 weighted proton images were obtained for identification of the prostate boundary, and quantitative sodium images were acquired with 1 mm isotropic resolution. In the prostates of 5 healthy mice, the mean sodium concentration was 130±14 mM. In future experiments, this quantitative sodium imaging technique will be applied to a transgenic mouse model of prostate cancer to determine if sodium concentrations are altered in cancerous prostate tissue.

                  2471.     A Triple-Resonant RF Coil Setup for 1H, 23Na and 39K MR Imaging of the Rat Brain at 9.4T

Mark Aurel Augath1,2, Patrick Heiler1, Stefan Kirsch1, Lothar R. Schad1

1Computer Assisted Clinical Medicine, Faculty of Medicine Mannheim, University of Heidelberg, Mannheim, Germany; 2Dept. Physiology of Cognitive Processes, Max-Planck-Institute for Biological Cybernetics, Tuebingen, Germany

The measurement of the spatial distribution of pathologically changing ion concentrations of 23Na and 39K could offer a very promising approach in clinical diagnostics. For MR imaging of both elements and the acquisition of anatomical proton images in the same experiment without moving the subject or the RF coil we developped a triple-resonant RF coil setup for the rat head at 9.4T. Two perpendicular Helmholtz pairs for 23Na and 39K delivered a good homogeneity over the sample volume. The flat double-D 1H surface coil showed no signs of coupling with the other coils and good coverage for shimming and anatomical images.

                  2472.     Improved Quantitative Sodium Imaging with a Flexible Twisted Projection Design and B0 Inhomogeneity Correction

Aiming Lu1, Frederick C. Damen1, Ian C. Atkinson1, Theodore Claiborne1, Keith R. Thulborn1

1Center for MR Research, Univ. of Illinois at Chicago, Chicago, IL, USA

Quantitative sodium MRI can provide vital information on tissue viability in diseases such as stroke and brain tumors. While TPI is an efficient sequence for quantifying tissue sodium concentration, its performance is compromised by its gradient waveform design. Moreover, the extended readout time employed in TPI renders its sensitivity to B0 field inhomogeneity artifacts. A scheme allowing for more flexible and efficient TPI waveform design is proposed here. B0 field inhomogeneities were corrected using field maps obtained quickly from co-registered 1H imaging. High quality quantitative sodium images have been achieved within acceptable times on a clinical 3T scanner.

                  2473.     Measurement of Post-Exercise Phosphocreatine Recovery Kinetics in Muscle Using 31P RARE MRI

Robert L. Greenman1, Howard A. Smithline2

1Radiology, Harvard University Medical School and Beth Israel Deaconess Medical Center, Boston, MA, USA; 2Emergency Medicine, Tufts University School of Medicine and Baystate Medical Center, Springfield, MA, USA

The phosphocreatine (PCr) recovery rate in muscle following exercise can be used as a measure of mitochondrial function. Dynamic phosphorus-31 (31P) magnetic resonance spectroscopy (MRS) can measure PCr recovery in exercise physiology and in disease states. Currently, Dynamic 31P MRS is performed using only surface coil localization. A method that can acquire PCr recovery information uniformly from a cross section of a human limb may be provide insights into the mitochondrial function of different muscles within the region simultaneously. We have measured spatially localized PCr recovery in a human limb using the Rapid Acquisition with Relaxation Enhancement (RARE) sequence.

 
Electron Spin Resonance
Exhibit Hall 2-3                    Monday 14:00-16:00 

                  2474.     Rapid EPR Oximetry Using Sparse Spin Distribution

Subhojit Som1, Lee C. Potter, Rizwan Ahmad2, Deepti S. Vikram3, Periannan Kuppusamy2

1Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH, USA Minor Outlying Islands; 2Davis Heart and Lung Research Institute, Department of Internal Medicine,, The Ohio State University, Columbus, OH, USA; 3Davis Heart and Lung Research Institute, Department of Internal Medicine,, The Ohio State University, Colmbus, OH, USA

A method is presented to use continuous wave electron paramagnetic resonance (EPR) imaging for rapid measurement of partial pressure of oxygen in three spatial dimensions. A particulate paramagnetic probe is employed to create a sparse distribution of spins in a volume of interest. Reduction of unknown parameters is achieved by using a parametric forward model and exploiting the sparsity of spin distribution. This leads to an order of magnitude reduction in data acquisition time as compared to tradition spectral-spatial imaging. The proposed oximetry method is experimentally demonstrated using an L-band EPR spectrometer.

                  2475.     Experimental Setup for DNP Spectroscopy and Variable Field Proton Electron Double Resonance Imaging

Alexandre Samouilov1, Eric Kesserling1, Sergey Petryakov1, Keerthi Shet1, Ziqi Sun1, David J. Lurie2, Jay L. Zweier1

1Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA; 2Department of Bio-Medical Physics and Bio-Engineering, University of Aberdeen, Aberdeen, UK

A variable field system capable of performing DNP spectroscopy and variable field PEDRI with NMR detection at any magnetic field in the range 0 - 0.38 T is described. The system is built around a clinical MRI electromagnet. To obtain EPR spectral characteristics, partial cancellation of the detection NMR field is required to alter the evolution EPR field at which the electron paramagnetic resonance excitation is achieved. The addition of resistive field cancellation coils in the gap of the primary magnet provides this fast offset in the range of 0–0.1 T.

                  2476.     Influence of Paramagnetic Changes in Cytochrome c on T2-Weighted MRI of G93A-SOD1 Transgenic ALS Mice

Karunakaran Chandran1, Xiping Liu1, Donna McAllister1, Vinai Roopchansingh1, B. Douglas Ward1, William E. Antholine1, Joy Joseph1, Shi-Jiang Li1, B. Kalyanaraman1

1Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA

The role of mitochondrial dysfunction in amyotrophic lateral sclerosis (ALS) is well established. In this study we have combined the EPR and MRI techniques to better understand the changes in the MR signal intensity detected in a preclinical ALS mouse model. Low-temperature EPR data indicate that cytochrome c release from mitochondria during ALS progression correlates with the observed T2 increase in brain stem of ALS mice. The T2 hyperintensity may be attributed to increased spin conversion from a low spin iron (S=1/2) to a high spin iron (S=5/2) of cytochrome c in ALS brain stem tissues.

                  2477.     Development of Fast CW-EPR Imaging

Hideo Sato-Akaba1, Hirotada Fujii2, Hiroshi Hirata1

1Division of Bioengineering and Bioinformatics, Hokkaido University, Sapporo, Hokkaido, Japan; 2School of Health Sciences, Sapporo Medical University, Sapporo, Hokkaido, Japan

To visualize the distribution of free radicals with a short lifetime, the temporal resolution of three-dimensional (3D) EPR imaging should be several times shorter than the lifetime of the free radicals. The purpose of the present work was to further reduce the acquisition time for 3D EPR imaging to improve the temporal resolution. An acquisition time of 5.8 s was achieved under conditions of 46 projections and a field-scan frequency of 9 Hz. This is 5 times faster than that previously reported for a 650-MHz CW-EPR imaging apparatus, which makes it possible to acquire 3D projection data in 30 s.

                  2478.     Simultaneous EPR 3D Image Reconstruction and Visualization During Acquisition of Projection Data

Hideo Sato-Akaba1, Hiroshi Hirata1

1Division of Bioengineering and Bioinformatics, Hokkaido University, Sapporo, Hokkaido, Japan

Electron paramagnetic resonance imaging (EPRI) allows the visualization of@free radicals in biological samples. To investigate the reduction of spin probes, the acquisition of 3D projection data has recently been achieved in 30 s in a live animal experiment and 6 s in a phantom experiment. However, image reconstruction and visualization of 3D objects were carried out after the data acquisition, which takes more time than the data acquisition itself. We report here the development of EPR imaging software that can reconstruct a 3D image while simultaneously acquiring projection data, and can visualize a 3D image immediately after reconstructing it.

                  2479.     In Vivo Electron Paramagnetic Resonance Detects Oxidative Stress in Skeletal Muscle After Burn Trauma

Nadeem Khan1, Sriram P. Mupparaju1, Dionyssios Mintzopoulos2,3, Meenu Kesarwani2,4, Valeria Righi2,3, Laurence G. Rahme2,5, Harold M. Swartz1, A Aria Tzika2,3

1EPR Center for Viable Systems, Department of Diagnostic Radiology, Dartmouth Medical School, Hanover, NH, USA; 2NMR Surgical Laboratory, MGH & Shriners Hospitals, Harvard Medical School, Boston, MA, USA; 3Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Boston, MA, USA; 4Molecular Surgical Laboratory, MGH & Shriners Hospitals, Harvard Medical School, Boston, MA; 5Molecular Surgical Laboratory, MGH & Shriners Hospitals, Harvard Medical School, Boston, MA, USA

Using in vivo electron paramagnetic resonance (EPR) on a 1.2 GHz (L-band) EPR spectrometer, we longitudinally evaluated oxidative stress in a burn trauma model to the left hind limb of mice. The EPR measurements confirm genomic results, which indicated down-regulation of antioxidant genes and strongly suggest dysfunction of the mitochondrial oxidative system. Thus, EPR, which allows the direct measurement of tissue parameters such as pO2, redox status, and reactive oxygen species (ROS), may be used to complement nuclear magnetic resonance (NMR), to better assess tissue damage and the therapeutic effectiveness of antioxidant agents in burn trauma.

                  2480.     Resonator for Co-Registration EPR/NMR Imaging and Spectroscopy

Sergey V. Petryakov1, Alexandre Samoulilov1, Eric Kesselring1, Jay L. Zweier1

1Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University, Columbus, OH, USA

The development of a double frequency resonator for co-registering EPR/NMR imaging is reported. The resonator is capable of working at frequencies: 16.18 MHz for NMR and 1.2 GHz for EPR and is designed for small animals and isolated rat heart experiments. The resonator measures 22 mm in diameter, 19 mm in length. The resonator is a one side fed, two quarter-wave shorted gap one loop resonator for EPR and simultaneously it is a single turn, flat-loop coil for NMR. Using the same loop for two modalities maximizes filling factor at both frequencies. ACC (30 dB) and ATC (8 MHz) capability are incorporated in the EPR part of the resonator to reduce motional noise effect.

                  2481.     Variation of the Overhauser Enhancement with Field-Cycling

David J. Lurie1, Keerthi Shet2, George L. Caia2, Eric Kesselring2, Sergey Petryakov2, Alexandre Samouilov2, Jay L. Zweier2

1Biomedical Physics, University of Aberdeen, Aberdeen, Scotland, UK; 2Ohio State University, Columbus, OH, USA

Dynamic nuclear polarization (DNP) enables detection and spectral characterization of paramagnetic substances, measured as a transfer of polarization from the unpaired electron to the nuclear spin. The polarization transfer leads to the Overhauser enhancement (OE). In field-cycled DNP the magnetic field is ramped down for electron excitation and ramped up for NMR detection. This study investigates the variation of OE with field-cycling. The OE decreased and the SNR of the DNP experiment increased as the NMR detection field was varied as 100 G, 200 G and 587 G and the electron irradiation field was maintained constant at 100 G.

 
Microscopy & Perfusion Imaging
Exhibit Hall 2-3                    Tuesday 13:30-15:30

                  2482.     μMRI Optimisation for Phenotyping the Embryo Mouse Heart

Jon Orlando Cleary1,2, Anthony Nathan Price1, David L. Thomas2,3, Peter J. Scambler4, Vanessa Kyriakopoulou4, Roger J. Ordidge2,3, Mark Francis Lythgoe1

1Centre for Advanced Biomedical Imaging, University College London, London, UK; 2Department of Medical Physics and Bioengineering, University College London, London, UK; 3Wellcome Trust Advanced MRI Laboratory, University College London, London, UK; 4Molecular Medicine Unit, UCL Institute of Child Health, London, UK

Phenotyping transgenic mice advances the study of gene function in cardiac development and disease. µMRI – an emerging technique for mouse embryo screening – usually relies on the use of fixative containing gadolinium-chelate, resulting in reduced tissue T1 and higher signal in short TR sequences used for high-resolution scans. There is little data on fixation time, Gd concentration and contrast optimisation for imaging of embryos in the literature. We present a study to improve contrast in the embryo heart through preparation and MR scan parameter optimisation. We then applied this to screening embryos heterozygous for the gene Chd7, implicated in CHARGE syndrome.

                  2483.     Quantitative MR Microscopy of the Liver and Kidneys in a Mouse Model of Polycystic Kidney Disease (PKD)

Choong-Heon Lee1,2, Jeremy J. Flint2,3, Lisa Guay-Woodford4, Stephen J. Blackband3,5

1Electrical and Computer Engineering, University of Florida, Gainesville, FL, USA; 2McKnight Brain Institute, University of Florida, Gainesville, FL, USA; 3Neuroscience, University of Florida, Gainesville, FL, USA; 4Genetics, University of Alabama, Birmingham, AL, USA; 5National High Magnetic Field Laboratory, Tallahassee, FL, USA

Polycystic kidney disease (PKD) is a major cause of end-stage renal disease in humans. Here we apply MR microscopy for evaluating the structural abnormalities involving ductal structures in the kidney and liver of the cpk mouse model of recessive PKD. MR microscopy of the excised tissues differentiates between wild type and mutant mouse kidney and liver, and also shows a significant difference in the volume fraction of the biliary ducts to total liver volume. These results suggest that MRM may play a role in evaluating genetic models of PKD, quantitating variance for genetic modifier studies and monitoring of potential therapies.

                  2484.     Extend Your Conventional Animal MRI to a Microimaging System

Hans Weber1, Dominik Paul1, Jürgen Hennig1, Dominik von Elverfeldt1

1Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany

MR microscopy offers the great potential to apply anatomical, functional and spectroscopic MR techniques to small objects or small regions of interest with high SNR. With the Coil-on-a-Chip technology (BrukerBioSpin AG, Switzerland), highly sensitive microcoils are available on the market for high resolution imaging in NMR spectrometers. In this work, we show that these microcoils can be integrated and used in a conventional animal MRI system without any changes in hardware architecture, resulting in images with high SNR and high resolution.

                  2485.     MR Investigation of a Teratogen-Mediated Mouse Model of Cleft Lip Palate

Robert J. Lipinski1, Wade Bushman1, Ian J. Rowland2

1Department of Urology, University of Wisconsin - Madison, Madison, WI, USA; 2Department of Radiology, University of Wisconsin - Madison, Madison, WI, USA

In utero exposure to the teratogen cyclopamine produces orofacial defects in mice that phenotypically mimic human cleft lip and palate defects. Using 3D MR imaging of E16.5 mouse embryos soaked in contrast agent, the fidelity of the model has been investigated. External clefts of the lip were visualized by 3D volumetric rendering while internal cleft palate defects were easily identifiable in 2D virtual sections. These studies establish the suitability of MRI to phenotypically assess embryonic mouse models.of developmental defects.

                  2486.     Achieving Equilibrium in Active Staining for MRI of Fixed Mouse Brain

Michael David Wong1, Sharon Portnoy1, Christine Laliberté1, R Mark Henkelman1

1Mouse Imaging Centre, Hospital for Sick Children, Toronto, Ontario, Canada

Active staining of fixed mouse brain with gadolinium based contrast agents can drastically improve image quality. Our study demonstrates a new active staining protocol where the concentration of contrast agent during perfusion is proportional to the ratio of brain volume to brain blood volume. With this protocol the brains reach equilibrium with the contrast agent approximately 2 times faster than with traditional active staining protocols.

                  2487.     Compressed Sensing for Multiple Mouse Whole Body MRI

Jonathan Bishop1, R Mark Henkelman1

1Hospital for Sick Children, Toronto, ON, Canada

There are conflicting requirements for temporal resolution of the heart and spatial resolution of the body in multiple mouse whole body MRI. A simulation study was performed to evaluate the potential of compressed sensing for improving image reconstruction quality under conditions of temporal undersampling.

                  2488.     Monitoring Degradation of Implantable Drug Delivery Devices Using MR Relaxation & Diffusion Imaging

Josh M. Bray1,2, Mark Filiaggi3, Chris V. Bowen1,4, Steven D. Beyea1,4

1Institute for Biodiagnostics (Atlantic), National Research Council Canada, Halifax, Nova Scotia, Canada; 2Dept. of Physics, Dalhousie University, Halifax, Nova Scotia, Canada; 3School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada; 4Depts of Physics, & Radiology, School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada

Biodegradable ceramics offer considerable advantages as drug delivery devices, as they require no secondary surgery and their microstructure may be modified to control the rate of local delivery of the therapeutic agent. The current work reports on the use of high resolution mapping of T1 and T2 relaxation times as well as ADC in gelled calcium polyphosphate bioceramics, in an attempt to develop an improved mechanistic understanding of their drug release characteristics.

                  2489.     Feasibility of Arterial Input Functions from Phase Data in T1-Weighted Dynamic Contrast-Enhanced MRI

Anders Garpebring1, Nils Östlund2, Mikael Karlsson1

1Radiation Sciences, Umeå University, Umeå, Sweden; 2Biomedical Engineering and Informatics, Umeå University Hospital, Umeå, Sweden

The magnitude signal in T1-weighted DCE-MRI only has high sensitivity to a limited range of contrast agent concentrations, which makes simultaneous measurement of contrast agent concentration in tissue and the arterial input function (AIF) difficult. The aim of this study was to determine if the phase information from a sequence optimized for the contrast levels in a tumor can be used for measurement of the AIF. A flow-phantom was used to investigate accuracy, precision and linearity of concentrations derived from phase data. The results showed that the phase is well suited for the determination of the AIF.

                  2490.     Quantification of Blood Volume and Transvascular Water Exchange Using Gd-DTPA in Mouse Brain

Young Ro Kim1, Guangping Dai1, Shuning Huang1,2, Peter Caravan1, Alexei Bogdanov3, Bruce Ro Rosen1

1Athinoula Martinos Center for Biomedical Imaging/ Massachusetts General Hospital, Charlestown, MA, USA; 2Health Science and Technology, Massachusetts Institute of Technology, Cambridge, MA, USA; 3University of Massachusetts School of Medicine, Worcester, MA, USA

We have developed a novel MRI scheme with corrections for T2* signal contribution for quantifying relative transvascular water exchange rate (WER) across non-leaky vascular membranes (i.e., BBB) and absolute cerebral blood volume (CBV), irrespective of the time-dependence of systemic contrast agent (e.g., Gd-DTPA: MW ~500 Da) concentration. Using normal wild type mouse models, we compared regional WER and CBV (cortex vs. striatum) determined by the typical macromolecular approach (Gd-PGC: MW ~500,000 Da) with the results acquired with the proposed method using the widely available Gd-DTPA. Despite the severe time dependence of the blood Gd-DTPA concentration, the measured CBV and WER were similar to those quantified by the traditional macromolecular method.

                  2491.     Comparison of Transvascular Water Exchange Between Mannitol and CO2 Challenges

Shuning Huang1,2, Guangping Dai2, Alexei Bogdano3, Bruce R. Rosen1,2, Young Ro Kim2

1Health Science and Technology, MIT, Cambridge, MA, USA; 2Martinos Center for Biomedical Imaging, MGH, Charlestown, MA, USA; 3Medical School, University of Massachusetts, Worcester, MA, USA

Previous studies have shown that trans-vascular water movement (i.e. intra-/extra-vascular water exchange rate: WER) and cerebral blood volume (CBV) can be quantified using a 3D spoiled gradient echo and a long-circulating intravascular contrast agent (Gd-PGC). In the current study, we used two well-known cerebrovascular perturbations, i.e. intravenous Mannitol injection and CO2 challenges (1) to show that CBV and WER can be simultaneously and independently measured and (2) investigate the possible mechanistic differences between the two challenges.

                  2492.     Comparison of Baseline Cerebrovascular Changes Between ENOS Knockout and Wild Type Mice

Shuning Huang1,2, Dmitriy Atochin3, Guangping Dai2, Alexei Bogdano4, Paul L. Huang3, Bruce R. Rosen1,2, Young Ro Kim2

1Health Science and Technology, MIT, Cambridge, MA, USA; 2Martinos Center for Biomedical Imaging, MGH, Charlestown, MA, USA; 33CVRC, Department of Cardiology, MGH, Charlestown, MA, USA; 4Medical School, University of Massachusetts, Worcester, MA, USA

Endothelia-derived nitric oxide plays an important role in regulating vascular tone and maintaining blood pressure. eNOS knockout mouse model has been extensively used to study eNOS function in various cerebrovascular diseases. Understanding baseline changes of vascular parameters in eNOS knockout mice may further aid the investigation of eNOS functions under pathological conditions including hypertension. In this study, we established baseline MR-derived cerebrovascular parameters in eNOS knockout mice, and demonstrated that eNOS can affect both vascular geometry and function under normal physiological conditions.

                  2493.     Brain Capillary Water Permeability from Proton Density 1H2O Imaging in the Rat During Deuterated Saline Bolus Passage

Audrey H. Selzer1, William D. Rooney1, Thomas M. Barbara1, James A. Goodman1, Charles S. Springer Jr. 1, Xin Li1

1Advanced Imaging Research Center, Oregon Health and Science University, Portland, OR, USA

In vivo intercompartmental water exchange has been studied extensively using labeled water. Here we use proton imaging to monitor the 2HOH concentration change during a bolus injection of deuterated saline solution, and thence measure non-equilibrium transendothelial water transport. This provides a direct comparison of MRI results of water transport with those from other methods.

                  2494.     The Effects of Parameter Assignment Variation Using a Reference Region Model on Dynamic Contrast Enhanced Magnetic Resonance Imaging (DCE-MRI)

Mary E. Loveless1,2, Anthony Z. Faranesh3, John C. Gore1,2, Thomas E. Yankeelov1,2

1Biomedical Engineering, Vanderbilt University, Nashville, TN, USA; 2Institute  of Imaging Science, Vanderbilt University, Nashville, TN, USA; 3Translational Medicine Branch, National Heart Lung and Blood Institute (NIH), Bethesda, MA, USA

This study interrogates error propagation in reference region models used in DCE-MRI by examining the variation in reference region parameter assignment. Differences in these required a priori values can lead to errors in estimated target-of-interest parameters. Simulations found that initial reference region parameters, including the vascular term, can vary by ~ 38% and still achieve <25% target parameter error. Experiments are currently ongoing to test this hypothesis.

                  2495.     Relative Recirculation Abnormalities in Collapsed Lung: A Metric for Vascular Tortuosity?

Christopher K. Macgowan1,2, Shengping Wu2, Rogerio Tessler3, Jaques Belik2,4, Andrea Kassner2,5

1Medical Biophysics, University of Toronto, Toronto, ON, Canada; 2Physiology and Experimental Medicine, Hospital for Sick Children, Toronto, ON, Canada; 3Pediatrics, Pontifcia Universidade Catolica do Rio Grande do Sul, Rio Grande do Sul, Brazil; 4Pediatrics, University of Toronto, Toronto, ON, Canada; 5Medical Imaging, University of Toronto, Toronto, ON, Canada

Respiratory distress syndrome (RDS) affects approximately 1% of newborn children and is the leading cause of death in pre-term infants. It is characterized by regional lung collapse (atelectasis) resulting from low surfactant production in the immature lung. Atelectasis results in shortening and folding of the alveolar walls, leading to abnormal and tortuous microvasculature. Relative recirculation (rR) obtained from dynamic perfusion MRI has been proposed previously as a metric of microvessel tortuosity. Our findings show increased rR values in the collapsed lung which we believe is associated with acute architectural remodeling.

                  2496.     About the Limitations of the PS-Limited Tofts Model

Guido Correia Carreira1, Dirk Beyersdorff2, Lutz Luedemann3

1Radiology, Charite Medical School, Berlin, Germany; 2Radiology, Bethel Hospital, Berlin, Germany; 3Charite Medical School, Germany

Little systematic work has been done on the limitations of compartment models. This work shows that compartment models may indicate a variation of vessel permeability and extracellular fractional volume even when there is no such change in these tissue parameters, but in different ones like for example vessel distance. To this end, numerical diffusion simulations for several tissue models, describing the CM distribution process at the microscopic scale, are compared with a standard PS-limited (low permeability) two-compartment Tofts model.

                  2497.     Model Selection in High Temporal Resolution DCE-MRI of Breast Tumors

Robert Luypaert1, Smitha Makkat, Johan De Mey, Steven Sourbron2

1UZ Brussel  - Radiology/BEFY, Vrije Universiteit Brussel, Brussels, BE, Belgium; 2Josef Lissner Laboratory for Biomedical Imaging, Ludwig-Maximilian-University, Munich, Germany

Assessment of tumor blood flow and permeability is important for breast cancer treatment. High temporal resolution T1-DCE-MRI and deconvolution provide model independent blood flow values. Extracting permeability information needs model-based analysis. 21 histologically proven breast tumors were examined. The inversion-prepared TFE time courses covered 140s at a temporal resolution of 0.3s. ROI data were fitted to the 2-compartment exchange, modified Tofts and uptake models. The Akaike information criterion was used to investigate which model fitted the data best. Result: in 70% of cases one model was at least twice as likely as the next to be the best.

                  2498.     Assessement of Blood Volume Fraction Using MRI: Characterization in Silico of Possible Bias

Thomas Christen1,2, Nicolas Joudiou1,2, Nicolas Pannetier1,2, Sebastien Reyt1,2, Christoph Segebarth1,2, Chantal Rémy1,2, Emmanuel L. Barbier1,2

1Inserm, U836, Grenoble, F-38043, France; 2Université Joseph Fourier, Grenoble Institut des Neurosciences, UMR-S836, Grenoble, France

MR seems to overestimates blood volume fraction (BVf) in healthy and tumoral tissues. The straight cylinder vessel modeling generally made in MR might be inadequate.This study shows that BVf estimates are not strongly influenced by either vessel shape or vessel curvature but are biased by preferential orientation of vessel or vessel density. MR estimates of BVf are overestimated by about 20% for normal intervessel distances. This systematic error on BVf estimate could be due to the interaction between the magnetic susceptibility gradients originating from neighbour cylinders.

 
Methodology for MR Elastography
Exhibit Hall 2-3                    Wednesday 13:30-15:30

                  2499.     Multifrequency MR Elastography on Human Thigh Muscle in Relaxation and in Contraction

Dieter Klatt1, Uwe Hamhaber2, Sebastian Papazoglou1, Katrin Rettig1, Hasan Nuzha1, Juergen Braun2, Ingolf Sack1

1Dept. of Radiology, Charite - University Medicine, Berlin, Germany; 2Inst. of Medical Informatics, Charite - University Medicine, Berlin, Germany

In this study the quadriceps femoris muscles of four volunteers were examined in relaxation and in contraction by multifrequency MR elastography. The rheological springpot model was used for calculating viscoelastic parameters by fitting its dispersion relations to the measured values of the complex shear modulus. Both parameters of the springpot model, α and μ, revealed higher values in the contracted muscle than in the relaxed muscle. The correlation of the α-parameter with the condition of the muscle indicates that muscle contraction causes a structural reordering of tissue building blocks.

                  2500.     In-Vivo Brain Viscoelastic Anisotropic Properties Using DTI and MR-Elastography

Michael A. Green1, Lynne E. Bilston1, Elijah Van Houten2, Ralph Sinkus3

1Prince of Wales Medical Research Institute, Sydney, Australia; 2University of Canterbury, Christchurch, New Zealand; 3Laboratoire Ondes et Acoustique, ESPCI, Paris, France

This study presents the first measurements of anisotropic viscoelastic brain properties obtained with a combination of DTI and MR-Elastography techniques. DTI measurements were used to assign the local fibre direction axis for insertion into the inverse elasticity wave equation. The shear moduli fractional anisotropy values were calculated for grey and white matter in the cerebrum and cerebellum. Thus, comparisons are made between mechanical and diffusive fractional anisotropy in different brain regions of healthy subjects.

                  2501.     Magnetic Resonance Elastography in Bounded Media

Arunark Kolipaka1, Kiaran P. McGee1, Armando Manduca1, Kevin J. Glaser1, Philip A. Araoz1, Richard L. Ehman1

1Department of Radiology, Mayo Clinic, Rochester, MN, USA

MR elastography (MRE) is a novel, MR-based method for spatially resolving the shear modulus of tissue-like materials. Current MRE estimates of shear modulus do not include geometric considerations and therefore can potentially underestimate this value. The aim of the study is to extend MRE methods to two objects in which geometric considerations are included, namely a beam and spherical shell. Validation of these models was performed by comparing MRE stiffness values to those obtained from finite element modeling and pressure-volume estimates.

                  2502.     A Dual-Stage Reconstruction Algorithm for Magnetic Resonance Elastography

Elijah Evenstar Wallace Van Houten1, Ralph Sinkus2

1Department of Mechanical Engineering, University of Canterbury, Christchurch, Canterbury, New Zealand; 2Laboratoire Ondes et Acoustique, l'Ecole Supérieure de Physique et de Chimie Industrielles, Paris, France

This paper presents a novel, dual-stage elastic property reconstruction method for Magnetic Resonance Elastography which provides improved fidelity over fast, direct reconstruction methods while also improving convergence time for an optimisation based reconstruction method. Results are presented in both phantom and in-vivo data.

                  2503.     In Vivo MR Elastography of Liver: Comparison to Oscillatory Rheometer Studies of Tissue Specimen

Dieter Klatt1, Christian Friedrich2, Asbach Patrick1, Hasan Nuzha1, Katrin Rettig1, Sebastian Papazoglou1, Uwe Hamhaber3, Juergen Braun3, Ingolf Sack1

1Dept. of Radiology, Charite - University Medicine, Berlin, Germany; 2Materials Research Center, University of Freiburg, Germany; 3Inst. of Medical Informatics, Charite - University Medicine, Berlin, Germany

MR elastography enables the measurement of the complex shear modulus of living soft tissue at multiple driving frequencies. The resulting dispersion function indicates microstructural tissue properties which significantly change through disease. In this study, bovine liver specimens were investigated by oscillatory rheometry. Below 50 Hz driving frequency, the observed modulus dispersion followed a powerlaw in good approximation. This observation agrees to in vivo multifrequency MRE data of healthy human liver suggesting the use of the two-parameter springpot model in liver MRE.

                  2504.     MR Elastography at 7T to Measure Tissue Biomechanical Properties for Improved Registration of Histopathology and Radiation Therapy Images

Deirdre Maria McGrath1, Warren D. Foltz1, Carolyn J. Niu1, Joanne L. Moseley1, Adil Al-Mayah1, Kristy K. Brock1,2

1Radiation Medicine Program, Princess Margaret Hospital, University Health Network,, Toronto, Ontario, Canada; 2Department of Radiation Oncology , University of Toronto , Toronto , Ontario, Canada

The registration of multi-modality images (e.g. MR, CT, PET), improves tumor identification for targeted cancer radiation therapy and correlation with 3D histopathologic maps may be used to validate identification of tumor boundaries. However fixation during pathology tissue processing deforms the tissue and changes material properties non-uniformly. Hence biomechanical registration methods (e.g. MORFEUS) require information on these changes. A quasi-static MR-elastography method has been developed at high field (7T), allowing rapid volumetric measures for whole organ resections, e.g. radical prostatectomy. An initial investigation has been carried out on fresh and fixed tissue and the results validated with measures from indentation testing.

                  2505.     Viscoelastic Shear Properties of the Cerebellum and Cerebrum Measured by MR-Elastography

Michael A. Green1, Lynne E. Bilston1, Elijah Van Houten2, Ralph Sinkus3

1Prince of Wales Medical Research Institute, Sydney, Australia; 2University of Canterbury, Christchurch, New Zealand; 3Laboratoire Ondes et Acoustique, ESPCI, Paris, France

High resolution in-vivo measurements of the viscoelastic brain properties in the cerebrum and cerebellum of healthy volunteers were obtained via 3D steady-state Magnetic Resonance Elastography. Coronal plane elastography images were obtained after optimising mechanical excitation and MR sequencing parameters. Quantified grey and white matter results indicate storage moduli are greater in the cerebrum than in the cerebellum. The latest values are lower than previously reported measurements and possible reasons are discussed.

                  2506.     Inversion Algorithm by Integral Type Reconstruction Formula for Magnetic Resonance Elastography

Mikio Suga1,2, Hisayuki Miura1, Hiroshi Fujiwara3, Takao Yamamoto4, Takashi Tanaka1, Qiuming YU5, Ken Arai1, Jian Ping GONG5, Gen Nakamura5, Hiroo Ikehira2, Takayuki Obata2

1Graduate School of Technology, Chiba University, Chiba, Japan; 2Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan; 3Graduate School of Informatics, Kyoto University; 4Faculty of Engineering, Gunma University; 5Graduate School of Science, Hokkaido University

Magnetic resonance elastography (MRE) can noninvasively visualize shear waves in tissue. One of the general approaches to estimating stiffness from MRE data is a local frequency estimation (LFE) algorithm, but the LFE estimate is blurred at sharp boundaries. Other methods are based on equations of motion, but they tend to be very sensitive to noise. In this study, we propose a new inversion algorithm that is applicable for noisy long shear wave images and the estimation of the shear modulus quantitatively with high spatial resolution. To confirm the reliability of this method, computer simulations and a phantom study were performed.

                  2507.     Comparison of Brain Viscoelasticity and Brain Volumetry in Healthy Volunteers

Ingolf Sack1, Kaspar Streitberger1, Uwe Hamhaber2, Dieter Klatt1, Sebastian Papazoglou1, Dagmar Krefting2, Jürgen Braun2

1Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany; 2Medical Informatics, Charité - Universitätsmedizin Berlin, Berlin, Germany

Magnetic resonance elastography (MRE) has shown to be the only suitable noninvasive method for determining viscoelastic properties of the living human brain. Brain stiffness and internal friction can change significantly due to neurodegenerative diseases. To assess the potential of MRE for an accurate differentiation and staging of such diseases, the influence of varying brain volumes on the quantification of viscoelastic properties was investigated. Preliminary results show, that no correlation exists between viscoelastic modules determined by MRE and normalized brain volumes. This indicates that MRE reveals independent and new information that is not influenced by brain atrophy.

                  2508.     Assessment of Hepatic Fibrosis in Liver Transplant Patients Using MR Elastography - Preliminary Results

Patrick Asbach1, Dieter Klatt1, Carsten Kamphues2, Peter Neuhaus2, Jürgen Braun3, Ingolf Sack1

1Department of Radiology, Charité University Hospital, Berlin, Germany; 2Department of General-, Visceral- and Transplantation Surgery, Charité University Hospital, Berlin, Germany; 3Department of Medical Informatics, Charité University Hospital, Berlin, Germany

Following liver transplantation viral re-infection of the graft frequently occurs and progression of fibrosis advances more quickly in the transplanted liver. The aim of the study was to investigate the potential of MR-elastography (MRE) in detecting liver fibrosis in transplant patients. MRE was applied to 10 patients with biopsy-proven liver fibrosis. Significant differences were found between the viscoelasticity of the liver of low-grade fibrosis patients (ì = 3.21 ± 0.27; mean ± SD) and high-grade fibrosis patients (ì = 5.19 ± 1.27). MR elastography has the potential to non-invasively detect liver fibrosis in transplant patients.

 
Outcomes: Cost Effectiveness, etc.
Exhibit Hall 2-3                    Wednesday 13:30-15:30

                  2509.     Reimbursement for Magnetic Resonance Spectroscopy

Alexander Peter Lin1,2, Verna Clements3, Thao Tran2, Brian David Ross2

1Biochemistry and Molecular Biophysics, California Institute of Technology, Pasadena, CA, USA; 2Huntington Medical Research Institutes, Pasadena, CA, USA; 3C.C.&C. Medical Billing Service, Los Angeles, CA, USA

It is popular belief that magnetic resonance spectroscopy is not reimbursed by the healthcare system however this is simply not true. MRS, CPT code 76390, is in fact reimbursed across the country with a national average of over $587.49 per exam. The goal of this study is to examine the history of reimbursement for MRS and to determine current reimbursement rates for this clinically important diagnostic tool. A brief discussion of effective MRS reimbursement strategies is also described.

                  2510.     A Policy for Management of Incidental Findings in Imaging Research

Melissa M. Jones1, Zoltan Patay1, Heather M. Conklin2, Clinton D. Hermes3, Fred H. Laningham4, Robert A. Kaufman1, Robert J. Ogg1

1Radiological Sciences, St. Jude Children's Research Hospital, Memphis, TN, USA; 2Behavioral Medicine, St. Jude Children's Research Hospital, Memphis, TN, USA; 3General Counsel, St. Jude Children's Research Hospital, Memphis, TN, USA; 4Children's Hospital Central California, Madera, CA

Management of incidental findings in imaging research is a challenging task facing the medical community. We report the elements of a policy developed for neuroimaging of healthy research participants, and summarize initial results of review of image data according to the new policy. The policy requires neuroradiologist review of scans, consensus opinion on categorization of findings, consent of research participants to be informed of findings and for referral to their health provider. We believe this policy balances the interests and responsibilities of participants and researchers, and hope dissemination will further the discussion in the imaging community toward establishing consensus guidelines.

                  2511.     fMRI Evaluation of Innovative Implantable Electrode for Peripheral Nerve Stimulation Animal Model

Rupeng Li1, Seth Jones2, Maida Parkins2, Christopher Pawela1, Mark Bosbous2, Ji-Geng Yan2, Hani S. Matloub2, James S. Hyde1

1Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA; 2Plastic Surgery, Medical College of Wisconsin, Milwaukee, WI, USA

This study provides a reliable tool for all the researchers dealing with survival study of PNS and CNS. It can both lower the research expense and simplify the research process, and potentially can be used on all kinds of animals in both fMRI and electrophysiology study.

                  2512.     Nephrogenic Systemic Fibrosis: Incidence Reduction with Screening and Use of Gadobenate Dimeglumine

Robert W. Garrett1, Andrew L. Wentland1, Arjang Djamali2, Anna Haemel3, Garima Agrawal1, Edwin Stanley4, Elizabeth A. Sadowski1

1Department of Radiology, University of Wisconsin, Madison, WI, USA; 2Department of Nephrology, University of Wisconsin, Madison, WI, USA; 3Department of Dermatology, University of Wisconsin, Madison, WI, USA; 4Department of Surgery, University of Wisconsin, Madison, WI, USA

The purpose of this study was to assess the impact of clinical guidelines developed at our institution to reduce the risk of nephrogenic systemic fibrosis (NSF)which included substituting gadobenate dimeglumine for gadodiamide in high risk patients. Retrospective analysis identified a group of high risk inpatients who received gadobenate dimeglumine over a one year period following NSF screening program implementation. This was compared with a similar population of high risk patients who received gadodiamide during the year prior to screening program implementation. There was a statistically significant reduction in NSF cases following implementation of these guidelines.

                  2513.     Changes in Properties of Polyvinyl Alcohol When Prepared Under a Deoxygenated Environment

Kyle Wilson1, R. Terry Thompson2, Gordon Campbell3, Gerald Moran4

1Medical Physics, McMaster University, Hamilton, ON, Canada; 2Lawson Imaging, London, ON, Canada; 3NRC, London, ON, Canada; 4Hamilton Health Sciences, Hamilton, ON, Canada

Several materials are currently used to mimic tissues depending on the imaging modality. Poly(vinyl alcohol) cryogel (PVA-C) has potential to be used as a multi-modality phantom. Its non-toxic, non-carcinogenic and biodegradable characteristics are advantageous. Thus, mapping of PVA-C properties would prove to be beneficial. By combining PVA with deionized water, heating for 2 hours and undergoing freeze/thaw cycles, PVA-C was produced in both ‘air’ and ‘nitrogen’ environments. PVA-C showed field dependence in T1, but this dependence was lost in samples produced in a nitrogen environment. Manipulating mechanical properties of PVA-C, yet keeping T1 constant, could prove beneficial in tissue mimicking.

                  2514.     Incidence of Nephrogenic Systemic Fibrosis at Chinese PLA General Hospital

Zhitong Zou1, Lin Ma1, Hengjin Li2

1Radiology, Chinese PLA General Hospital, Beijing, China; 2Dermatology and Dermatopathology, Chinese PLA General Hospital, Beijing, China

In order to assess the incidence of NSF at our large military hospital in China, we undertook a systematic search for cases of NSF and determined the number of patients receiving GBCA during the past 3.7 years for which computerized patient records are available. In spite of 28,680 injection of Gd:DTPA and 635 injection of gadobenate dimeglumine including 151 patients with GFR< 30ml/min or hemodialysis, there were no cases of NSF.

 
Thermal Therapy & Focused Ultrasound
Exhibit Hall 2-3                    Wednesday 13:30-15:30

                  2515.     MRI Thermometry of Near Field Cumulative Heating Induced by Successive HIFU Ablations

Charles Mougenot1,2, Max O. Köhler3, Bruno Quesson2, Ari Partanen3, Julia Enholm3, Chrit T. Moonen2, Teuvo Vaara3, Gösta J. Ehnholm3,4

1Philips Healthcare, Suresnes, France; 2Laboratory of Molecular and Functional Imaging, Bordeaux, France; 3Philips Healthcare, Finland; 4Philips Research North America, USA

Reduction of treatment duration during focused ultrasound ablation, with too short cooling period, can in extreme cases may result in skin burns. Near field cumulative heating, where acoustic beam paths overlap, is difficult to predict with standard MR thermal map limited to the monitoring of single sonication duration. However cumulative MR thermal maps could be obtained with correction of baseline drift and transducer displacement susceptibility change. After 9 volumetric sonications performed on pig leg in vivo, the cumulative temperature is 5°C higher than standard temperature. As consequence cumulative temperature should be preferably used to detect skin heating.

                  2516.     Regularized Multicoil MR Thermometry

William Allyn Grissom1, Viola Rieke, John Pauly2, Nathan McDannold3, Kim Butts-Pauly

1Electrical Engineering and Radiology, Stanford University, Stanford, CA, USA; 2Electrical Engineering, Stanford University, Stanford, CA, USA; 3Harvard Medical School, Brigham & Women's Hospital, Boston, MA, USA

We present two new regularized iterative methods for estimating temperature change images from multicoil PRF-shift MR thermometry data. The first method uses baseline images acquired before thermal therapy, while the second is a reference-less method. Compared to conventional thermometry techniques, the new method is statistically motivated, generalizes to multicoil acquisitions, and is robust to noise. In addition, unlike conventional reference-less methods, the new reference-less method also does not require the user to track the heated region. We validate the new methods in simulations and experiments.

                  2517.     Robust Binary Feedback Control of MR Guided Volumetric HIFU Ablation

Max Oskar Köhler1, Julia Enholm1, Charles Mougenot2,3, Bruno Quesson3, Chrit T. W. Moonen3

1Philips Healthcare, Vantaa, Finland; 2Philips Healthcare, France; 3Laboratory of Molecular and Functional Imaging, University of Bordeaux 2, Bordeaux, France

A binary feedback control of the sonication duration was implemented and validated in-vivo on 11 male pigs. The feedback control reduced the outcome variability and the induced thermal lesion size was closer to that desired. The use of binary feedback in conjunction with volumetric ablation did not reduce the energy efficiency and the resulting thermal lesion also remained as homogeneous and well-defined as for non-feedback volumetric ablation.

                  2518.     Monitoring of HIFU Treatment Effectiveness by MR Imaging: An Ex-Vivo Studies with Multi-Spot Heating

En-Li Lin1, Hsu-Hsia Peng2, Teng-Yi Huang1, Yu-Shun Wang1, Wen-Shiang Chen3, Wen-Yih Isaac Tseng4

1Department of Electrical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan; 2Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan; 3Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taipei, Taiwan; 4Center for Optoelectronic Biomedicine, Medical College of National Taiwan University, Taipei, Taiwan

High intensity focused ultrasound (HIFU) provided tissue destruction or tumor ablation in a non-invasive way, which was one of the promising thermotherapy treatments. Our group has shown that magnetization-transfer-prepared (MT) gradient-echo sequence is a practical tool to simultaneously monitor the temperature change and MT contrast during HIFU energy transmission. Furthermore, we improved the previous experiment with a movable HIFU transducer mimicking the procedure of the MRIgFUS thermotherapy by multi-spot heating experiment and the efficiency of the MT/temperature measurement mapping was demonstrated in consecutive time. We can notice that the temperature rose after heating and fell gradually after turning off HIFU power, whereas the MT effect retained after heating. However, the MTR mapping was compatible to the widely used PRF-thermometry, which was to detect the tissue damage. In conclusion, this method that can monitor temperature changes as well as the level of MT change opens a potentially useful window to observe the tissue coagulation due to the HIFU power transmission in real-time.

                  2519.     Fast Volumetric Radiofrequency Current Density Imaging

Kim Shultz1, John Pauly1, Greig Scott1

1Electrical Engineering, Stanford University, Stanford, CA, USA

RF current density imaging (RFCDI) can potentially be used to monitor and predict RF ablation patterns. In order for RFCDI to be useful in a clinical setting, the acquisition process must be accelerated. Using the Actual Flip-Angle Imaging (AFI) technique to measure the magnitude and phase of the RF fields allows us to acquire volumetric current images with scan times of only a few minutes.

                  2520.     Proton Resonance Frequency Shift Weighted Imaging for the MR Monitoring of the Thermotherapy

Yi-Lu Tsai1, Jyun-Wen Chen1, Teng-Yi Huang1, Hsu-Hsia Peng2, Wen-Shiang Chen3, Wen-Yih Isaac Tseng4

1Dept. of Electrical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan; 2Dept. of Electrical Engineering, National Taiwan University, Taipei, Taiwan; 33.     Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taipei , Taiwan; 44.   Center for Optoelectronic Biomedicine, Medical College of National Taiwan University, Taipei, Taiwan

Owing to the temperature dependence of most MRI parameters such as the T1 and the proton density, the magnitude images obtained by the PRF-based sequences also exhibit temperature-related image contrast. In this study, we aimed to further enhance the contrast by a post-processing method similar to the recently advanced susceptibility-weighted imaging (SWI) method. In MRI-guided focused ultrasound (MRIgFUS) applications, the frequency dispersion induced by the local temperature elevation has the spin behavior similar to that of the susceptibility-related frequency shift. For this reason, we proposed to apply a SWI-like post-processing method, PRFSWI, to reconstruct the PRF-shift contrast for MRIgFUS.

                  2521.     Rapid FUS Focal Spot Localization Based on MR-ARFI.

Elena Kaye1,2, Jing Chen1,2, Kim Butts Pauly2

1Electrical Engineering, Stanford University, Palo Alto, CA, USA; 2Radiology, Stanford University, Palo Alto, CA, USA

For various therapeutic applications, focused ultrasound (FUS) is used in thermanl mode or mechanical mode. Mechanical mode has been used for temporary BBB disruption and for targeted drug delivery, but the monitoring of these treatments has been challenging since there no measurable temperature increase. This study investigates a single shot reduced FOV EPI for imaging tissue displacement induced by acoustic radiation force, ARFI, as a potential monitoring tool. The results of the study show that the focal spot of the mechanical mode FUS can be localized with the proposed technique, and that the measured displacement is comparable to the dispacement measured by previously proposed line scan technique.

                  2522.     Dynamic Susceptibility Induced Asymmetry of MR Proton Resonance Frequency (PRF) Thermometry Maps During Simultaneous RF Ablation Causing Large and Spatially Dependent Temperature Errors

Magalie Viallon1, Erik Dumont2, Joerg Roland3, Christoph D. Becker1, Sylvain Terraz1, Rares Salomir1

1Radiology, Geneva University Hospital, Geneva, Switzerland; 2Image Guided Therapy, PESSAC, France; 3R & D, Siemens Medical Solutions, Erlangen, Germany

Dynamic susceptibility induced asymmetry of MR proton resonance frequency (PRF) thermometry maps during simultaneous RF ablation causing large and spatially dependent temperature errors

                  2523.     Image-Guided Modulation of Regional Brain Function Mediated by Focused Ultrasound

Seung-Schik Yoo1, Alexander Bystritsky1,2, Jong-Hwan Lee1, YongZhi Zhang1, Krisztina Fischer1, Wonhye Lee1, Nathan McDannold1, Ferenc A. Jolesz1

1Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA; 2Psychiatry, UCLA, Los Angeles, CA, USA

Utilizing the minimally-invasive nature of the Focused ultrasound (FUS), selective modulation of regional neural activity in brain was sought after, and we found early evidence that FUS, as administered in train of pulses (i.e. focused ultrasound pulse: FUP), mediated reversible modulation of cortical activity in animal model.

                  2524.     First Human Application of Laser Interstitial Thermal Therapy in GBM Using MR Guided AutoLITT System

Stephen Jones1, Gene Barnett2, Jeffrey L. Sunshine3, Mark Griswold3, Andrew Sloan4, Micheal D. Phillips5, Richard Tyc6, Mark Torchia7

1Imaging Institute, Cleveland Clinic, Cleveland, OH, USA; 2Neurological Institute, Cleveland Clinic, Cleveland, OH, USA; 3Department of Radiology, University Hospitals Case Medical Center, Cleveland, OH; 4Department of Neurosurgery, University Hospitals Case Medical Center, Cleveland, OH; 5Imaging Institute, Cleveland Clinic, Cleveland , OH, USA; 6Monteris Medical Inc, Winnipeg, Manitoba, Canada; 7Department of surgery, University of Manitoba, Winnipeg, Manitoba, Canada

Glioblastoma (GB) is the most frequent primary brain malignancy in adults, usually resulting in death in 1-2 years despite decades of research. Although treatments such as surgery, chemotherapy, and radiation extend survival several months, recurrence is inevitable making minimally invasive therapies attractive. We describe the first human application of laser interstitial thermal therapy (LITT) of a GBM using the Monteris AutoLITT system. This system is unique in using real-time MRI thermometry to contour treatment precisely within the confines of the tumor. The AutoLITT produced thermal lesion appeared to stabilize after 48 hours and was accurately predicted by the AutoLITT software.

                  2525.     MRS Thermometry of the Brain Using Calibration Results of Aqueous Metabolite Solutions

Jan Weis1, Lucian Covaciu2, Sten Rubertsson2, Mats Allers3, Anders Lunderquist4, Francisco Ortiz-Nieto1, Håkan Ahlström1

1Dept. of Radiology, Uppsala University Hospital, Uppsala, Sweden; 2Dept. of Surgical Sciences, Anesthesiology and Intensive Care, Uppsala University Hospital, Uppsala, Sweden; 3Dept. of Clinical Sciences, Division of Thoracic Surgery, Lund University Hospital, Lund, Sweden; 4Dept. of Clinical Sciences, Division of Experimental Brain Research, Lund University Hospital, Lund, Sweden

Reliability of MRS brain temperature estimation is limited by accuracy of the calibration measurements of chemical shifts difference between water and metabolite lines. More accurate calibration data were obtained using NAA, glycerophosphocholine (GPC) and Cr aqueous solutions. Brain temperature of five healthy subjects was measured using Cho, Cr and NAA peaks. Volunteer’s mean brain and body (rectal) temperatures were 38.1±0.3 oC and 37.6±0.2oC, respectively. The fact that brain temperatures were 0.5±0.4 oC higher than body temperatures is in agreement with the literature. Calculations of the brain temperatures using Cho, Cr, and NAA references simultaneously improve reliability of the temperature estimations.

                  2526.     Comparison of Thermal Dose Models in Canine Brain Using the Dice Similarity Coefficient

Joshua Yung1, Anil Shetty1, Adam C. Springer1, Jeffrey Weinberg2, John D. Hazle1, Roger Jason Stafford1

1Imaging Physics, University of Texas M.D. Anderson Cancer Center, Houston, TX, USA; 2Neurosurgery, University of Texas M.D. Anderson Cancer Center, Houston, TX, USA

Various thermal dose models exist for predicting thermal damage from the temperature history provided by MRTI. However, within each model, different parameters or thresholds are often employed. In this work, the performance of multiple thermal dose models were compared using the Dice similarity coefficient (DSC) to determine the spatial overlap between predicted damage for in vivo canine brain during thermal therapy and post-treatment imaging. In all subjects, previously reported thresholds for each model resulted in a high DSC, but were improved by changes in thresholds, which could lead to a more accurate prediction of tissue response.

                  2527.     MR Temperature Mapping in Brain: A Comparison of the GRE, Segmented EPI and Ss EPI Sequences Based on the Proton-Resonance-Frequency-Method

Antje Kickhefel1, Joerg Roland2, Fritz Schick3

1Ernst-Moritz-Arndt University, Greifswald, Germany; 2Siemens, Erlangen, Germany; 3Eberhard-Karls University, Tuebingen, Germany

MR temperature mapping was performed with healthy volunteers using a gradient echo (GRE), a segmented EPI (seg EPI), and a single shot EPI (ss EPI) sequence at 1.5T and 3T using comparable acquisition parameters. The ss EPI sequence turned out as the fastest (100ms per slice) and most precise (0.2°C over 12 minutes on 3T) sequence in human brain. Heating of meat samples were measured for the GRE and the ss EPI sequence to show temperature measurement accuracy for the ss EPI. The results from seg EPI and GRE sequences were more robust against motion as well as other distortions.

                  2528.     Non Invasive Monitoring of the Brain Temperature During Mild Hypothermia

Jan Weis1, Lucian Covaciu2, Sten Rubertsson2, Mats Allers3, Anders Lunderquist4, Håkan Ahlström5

1Dept of Radiology, Uppsala University Hospital, Uppsala, Uppland, Sweden; 2Dept Surgical Sciences, Anesthesiology and Intensive Care, Uppsala University Hospital, Uppsala, Uppland, Sweden; 3Clinical Sciences, Div. of Thoracic Surgery, Lund University Hospital, Lund, Skane, Sweden; 4Clinical Sciences, Div. of  Exp. Brain Research, Lund University Hospital, Lund, Skane, Sweden; 5Dept. of Radiology, Uppsala University Hospital, Uppsala, Uppland, Sweden

Decrease of the pig’s brain temperature (~3 oC in 15 minutes) was induced by intranasal cooling. Conventional MRS methods are unsuitable for monitoring of such temperature changes because of poor spatial resolution and long acquisition time needed to obtain acceptable water-suppressed spectra. The actual brain temperature of six pigs was monitored by fiber optic probes and by MRSI with high spatial and reduced spectral resolution. The temperature coefficient of brain water chemical shift was measured without internal spectral reference. Our results indicate that the proposed MRSI method can be used for monitoring the brain temperature changes during controlled hypothermia.

                  2529.     MR-Guided Focused Ultrasound Ablation Through the Ribcage

Viola Rieke1, Randy Lee King1, Aravind Swaminathan1, Micheal V. McConnell1, Kim Butts Pauly1

1Stanford University, Stanford, CA, USA

For MR-guided FUS applications in the heart, a major limitation is the restricted acoustic window, due to the higher acoustic impedance of thoracic bone and cartilage compared to soft tissues. Here, we investigate if a human size ribcage provides enough acoustic window to ablate tissue in the heart. The results show that ablative temperatures can be reached with the acoustic windows provided, making FUS ablation in the heart a possibility.

                  2530.     Visualizing Acute RF Ablation Lesions in the Heart Using Non-Contrast MRI at 3T

Sathya Vijayakumar1, Eugene G. Kholmovski1, Rob S. MacLeod2,3, Josh Blauer4, Jayne Davis2, J. Rock Hadley1, Edward DiBella1,4, Kamal Vij5, Dennis L. Parker1, Nassir F. Marrouche6

1UCAIR, Dept. of Radiology, University of Utah, Salt Lake City, UT, USA; 2CVRTI, University of Utah, Salt Lake City, UT, USA; 3Dept. of BioEngineering , University of Utah, Salt Lake City, UT, USA; 4Dept. of BioEngineering, University of Utah, Salt Lake City, UT, USA; 5SurgiVision Inc., CA, USA; 6Cardiology, University of Utah, Salt Lake City, UT, USA

This work presents the use of non-contrast MRI sequences to detect and identify acute lesions caused by RF ablation in the heart. Canine experiments were performed to investigate how soon after delivery of RF power MRI can visualize lesion and whether it is observable in the atrium of the heart. Preliminary results indicate that acute lesion in the atrium of the heart can be visualized within a minute of delivering RF energy.

                  2531.     Registration and Visualization of Left Atrial Scar Due to Pulmonary Vein Ablation with Recorded Ablation Sites

Jason E. Taclas1, John V. Wylie1, Reza Nezafat1, Thomas H. Hauser1, Mark E. Josephson1, Jeff M. Hsing1, Warren J. Manning1, Dana C. Peters1

1Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA, USA

This project used the VTK and ITK open source C++ class libraries to develop a software application to register and display the left atrium after a radiofrequency pulmonary vein ablation procedure with CARTO electroanatomic mapping data, along with late gadolinium enhanced MR images of the resulting scar.

                  2532.     Heating of Fat Leads to Significant Temperature Errors in PRFS Based MR Thermometry

Sara Maria Sprinkhuizen1, Maurits K. Konings2, Chris J. Bakker1, Lambertus Wilhelmus Bartels1

1Image Sciences Institute, University Medical Center, Utrecht, Netherlands; 2Dept of  Medical Technology, University Medical Center, Utrecht, Netherlands

Reliable thermometry is a prerequisite during thermal therapy. The most widely used MR thermometry (MRT) technique is proton resonance frequency shift (PRFS) based MRT. In current practice, the only temperature dependent parameter which is exploited is the proton electron screening constant of water. The temperature dependence of the susceptibility is ignored. In this work, the impact of temperature induced susceptibility changes in fat on PRFS based MRT in the breast is quantified. Simulations are performed to calculate changes in the field distribution. Results show that the impact of these changes on PRFS based MR temperature maps is significant.

                  2533.     Temperature Dependence of Relaxation Times in Individual Fatty Acid Components and Its Consideration for MR Thermometry of Adipose Tissues

Kagayaki Kuroda1,2, Makoto Obara1,3, Marc Van Cauteren4, Masatoshi Honda5, Yutaka Imai5

1Graduate School of General Science and Technology, Tokai University, Hiratsuka, Kanagawa, Japan; 2Medical Device Development Center, Foundation for Biomedical Research and Innovation, Kobe, Hyogo, Japan; 3Medical Systems , Philips Electronics Japan, Tokyo, Japan; 4Medical Systems, Philips Electronics Japan, Tokyo, Japan; 5Department of Radiology, Tokai University, Isehara, Kanagawa, Japan

Temperature dependences of relaxation times in the individual fatty acid components in various samples in vitro were examined at 11T to provide a basis for quantitative temperature imaging of adipose tissues such as included in breast. T1 of both methylene chain and terminal methyl had linear relationships with temperature (r > 0.98), but the temperature coefficient for the two components differed significantly; those in five bovine fat samples were 11.6 ± 0.42 ms/deg C for methylene and 31.2 ± 3.92 ms/deg C for methyl. Numerical simulations based on the difference demonstrated that the inconsistency in the fatty acid component ratios for temperature calibration and estimation may cause considerable errors.

                  2534.     Breast Temperature Mapping Using Model-Based PRFS Method

Xinyi Pan1, Cheng Li1, Kui Ying1, Dehe Weng2, Wen Qin3, Kuncheng Li3

1Engineering Physics, Tsinghua University, Beijing, China; 2Siemens Mindit Magnetic Resonance Ltd. (SMMR), Shenzhen, Guangdong, China; 3Radiology, Xuanwu Hospital, Beijing, China

MR-guided thermal therapy has been used in the breast cancer treatment in which PRFS method is a promising noninvasive temperature monitoring tool. However, conventional phase mapping method is sensitive to respiratory motion, field drift, and widely distributed fat in the breast. A temperature model using fat as an internal reference has been proposed in our previous work to overcome aforementioned problems. In this work, the method is applied in the breast. The model and related algorithm are modified to be able to distinguish multiple species and tolerate low SNR. Its feasibility is demonstrated through a preliminary in vivo experiment.

                  2535.     Three Dimensional Targeting for Liver MRgFUS Based on Vessel Tree Tracking

Etsuko Kumamoto1, Yoshie Takao2, Daisuke Kokuryo3, Atsuya Okada4, Takamichi Murakami5, Toshiya Kaihara2, Kagayaki Kuroda6,7

1Information Science and Technology Center, Kobe University, Kobe, Hyogo, Japan; 2Graduate School of Engineering, Kobe University, Kobe, Japan; 3National Institute of Radiological Sciences, Chiba, Japan; 4Iseikai Hospital, Osaka, Japan; 5School of Medicine, Kinki University, Osaka, Japan; 6Graduate School of General Science and Technology, Tokai University, Hiratsuka, Kanagawa, Japan; 7Institute of of Biomedical Research and Innovation, Kobe, Hyogo, Japan

A three dimensional (3D) target tracking technique for MR-guided Focused Ultrasound Surgery (MRgFUS) of liver was proposed. This technique detects the through-plane motion and deformation of the tissue based on the 3D vessel tree structure and the along-plane displacements of the vessels in the saggital slices. Experiment with a healthy volunteer liver demonstrated that the vessel displacements through the sagittal plane reached 11.4mm indicating that the tissue motion and deformation in this direction is not negligible and hence such a three dimensional target tracking technique is necessary for a highly accuracy treatment of the moving organ.

                  2536.     A Rapid and Robust Method for Reducing Out-Of-Plane Motion in Dynamic Imaging. Application to MRI Thermometry on Abdominal Organs.

Thibault Carteret1, Mathilde Merle1, Gregory Maclair1, Baudouin denis de Senneville1, Chrit Moonen1, Bruno Quesson1

1CNRS/Université Bordeaux 2, Laboratory for Molecular and Functional Imaging, Bordeaux, France

MRI-thermometry on mobile organs requires minimal out-out-plane motion to efficiently monitor the temperature evolution. Local organ displacements were computed in orthogonal images acquired during free breathing and a Principal Component Analysis of the calculated motion field vectors was performed to determine the principal axis of motion and to correct the slice angulations in 3D. The resulting precision of MRI-thermometry in vivo on humans was significantly improved in the liver and kidney. This method only requires few minutes extra acquisition time and provides in addition the target trajectory in 3D, which can be included in the planning of the therapy.

                  2537.     Real Time Volumetric Temperature Imaging of High Intensity Focused Ultrasound Thermal Ablation on the Liver

Bruno Quesson1, Christophe Laurent2, Gregory Maclair1, Charles Mougenot3, Baudouin denis de Senneville1, Mario Ries1, Chrit Moonen1

1UMR5231 CNRS/Université Bordeaux 2, Laboratory for Molecular and Functional Imaging, Bordeaux, France; 2Hepatic Surgery, Centre Hospitalier Universitaire de Bordeaux, Bordeaux, France; 3Philips healthcare, Bordeaux, France

This study proposes a rapid and volumetric MR-thermometry during High Intensity Focused Ultrasound ablations performed in the liver of pigs. Several HIFU ablations were monitored in vivo with a multislice, motion compensated, single shot EPI sequence acquired at a 2.5Hz update rate/volume. Temperature standard deviation was about 1°C. Area were the thermal dose calculated online reached the lethal value were confirmed by histology results on the liver (ablation) and skin (no alteration). This work demonstrates the possibility to precisely monitor HIFU ablations with high temporal and spatial resolutions in vivo on a mobile organ and in the surrounding tissues (skin).

                  2538.     Transcatheter Intraarterial Perfusion (TRIP)-MRI Monitoring of Radiofrequency Ablation in Rabbit VX2 Liver Tumors

Dingxin Wang1, Kent Sato2, Johnathan Chung2, Richard Tang2, Rachel Klein2, Barbara Szolc-Kowalska3, Gayle Woloschak3, Reed Omary1,4, Andrew Larson1,4

1Departments of Radiology and Biomedical Engineering, Northwestern University, Chicago, IL, USA; 2Department of Radiology, Northwestern University, Chicago, IL, USA; 3Radiation Oncology, Northwestern University, Chicago, IL, USA; 4Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, IL, USA

4D TRIP-MRI offers the potential to objectively monitor serial changes in tumor perfusion during RFA therapies (rather than a single post-RFA confirmation measurement with current DCE approaches). Combined with current MR-thermometry approaches, TRIP-MRI may provide a useful tool for intra-procedural monitoring of coagulation zone formation by thermal ablation.

                  2539.     Optimization of Volumetric MR-Guided High-Intensity Focused Ulatrsound Ablations in Moving Organs

Silke Hey1, Baudouin Denis de Senneville1, Gregory Maclair1, Max O. Köhler2, Bruno Quesson1, Chrit T. W. Moonen1, Mario Ries1

1UMR 5231, CNRS/Université Bordeaux 2, Laboratory for Molecular and Functional Imaging, Bordeaux, France; 2Philips Healthcare, Vantaa, Finland

In this work, a method for the optimization of volumetric MR-guided high intensity focused ultrasound (HIFU) ablations is presented.

                  2540.     Patient Study of Realtime Magnetic Resonance Temperature Monitoring on Moving Organ Simultaneous to Laserinduced Thermal Therapy (LITT)

Antje Kickhefel1, Christian Rosenberg1, Joerg Roland2, Norbert Hosten1

1Ernst-Moritz-Arndt University, Greifswald, Germany; 2Siemens, Erlangen, Germany

MR thermometry based on the proton resonance frequency (PRF) was performed simultaneously to laserinduced thermotherapy (LITT) of liver tumors of free breathing patients. A temperature region (>55°C) was segmented in realtime images (2D-GRE) at the end of LITT. This segmented area was compared to the necrosis from 24 hours follow-up treatment (T1-weigthed 2D-FLASH). Registration between temperature imaging and follow-up was verified by segmentation of the entire liver with an averaged error of 5%. The temperature visualization overestimated/underestimated the necrosis with 12%/10%.

                  2541.     Experimental Study of Model-Based PRFS Method on Motion and Field Drift Effects

Xinyi Pan1, Cheng Li1, Kui Ying1, Dehe Weng2, Wen Qin3, Kuncheng Li3

1Engineering Physics, Tsinghua University, Beijing, China; 2Siemens Mindit Magnetic Resonance Ltd. (SMMR), Shenzhen, Guangdong, China; 3Radiology, Xuanwu Hospital, Beijing, China

MR temperature mapping based on a novel PRFS temperature model using fat as the internal reference previously proposed by us can greatly reduce the inter-scan motion or deformation and field drift induced quantification errors which are often encountered in conventional phase mapping PRF method. To validate such improvement, specific-designed phantom experiments were conducted to validate the feasibility of the model in handling motion and field drift related problems in this work. It is also demonstrated that the thermocouple probe induced susceptibility artifact in the temperature maps can be eliminated by the B-spline fitting of chemical shift.

                  2542.     Evaluation of Realtime Temperature Monitoring of Human Liver Based on Patients Undergoing a Radiofrequency Ablation

Antje Kickhefel1, Hansjoerg Rempp2, Joerg Roland3, Fritz Schick2

1Ernst-Moritz-Arndt University, Greifswald, Germany; 2Eberhard-Karls University, Tuebingen, Germany; 3Siemens, Erlangen, Germany

MR thermometry based on proton resonance frequency method (PRF) was performed during radio frequency ablation (RFA) (liver tumors; free breathing patients). A temperature region (>57°C) was segmented in real-time images (2D-GRE) at the end of LITT. These segmented areas were compared to the necrosis from 24hours follow-up measurements (T1-weigthed 3D-GRE). Registration between temperature imaging and follow-up was performed (averaged error 5%). Heated regions can be identified. Necrotic areas were overestimated (averaged ~5mm). In summary temperature visualization of the RFA is possible but has to be more reliable. Further improvement can be achieved by applying slice-by-slice respiratory triggering.

                  2543.     MRI-Guided Focused Ultrasound (MRgFUS) System for Thermal Ablation of Prostate Cancer: Pre-Clinical Evaluation in Canines

Nathan McDannold1, Hadas Ziso2, Benny Assif2, Arik Hananel2, Natalia Vykhodtseva1, Peri Gretton2, Magdalini Pilatou1, Steve Haker1, Clare Tempany1

1Harvard Medical School, Brigham & Women's Hospital, Boston, MA, USA; 2InSightec, Haifa, Israel

A transrectal MRgFUS system was tested in a canine prostate model. Focal volumes in each half of the prostate were targeted, with high energy in one half of the gland for ablation and on the other with lower-energy sonications to test our ability to localize the focal spot before causing thermal tissue damage. All sonications (n=155) were readily observed with proton resonance frequency (PRF) MR temperature imaging, contrast enhanced MRI and histology. The prostate gland moved during the experiments. The resultant focal temperature changes were 24.2±8.2°C.

                  2544.     Diffusion MRI and Contrast-Enhanced Monitoring of Prostate Microwave Focal Thermal Therapy: An In-Vivo Canine Study

Hai-Ling Margaret Cheng1,2, Masoom A. Haider3, Marcus J. Dill-Macky4, Joan M. Sweet5, John Trachtenberg6, Mark R. Gertner7,8

1Research Institute & Diagnostic Imaging, The Hospital for Sick Children, Toronto, Ontario, Canada; 2Medical Biophysics, University of Toronto, Toronto, Ontario, Canada; 3Medical Imaging, University Health Network and Mount Sinai Hospital; 4Pathology & Laboratory Medicine, University Health Network; 5Pathology & Laboratory Medicine, University Health Network, University of Toronto; 6Surgery, University Health Network; 7Biophysics & Bioimaging, University Health Network; 8Physics, Ryerson University

Diffusion MRI for monitoring thermal therapy has received much less attention than contrast-enhanced (CE) methods but is potentially more useful because of its repeatability. In this study, microwave heating of normal canine prostates was monitored with diffusion MRI, CE MRI, and CE ultrasound. CE images revealed an area of low uptake that was smaller than the red ring of thermal damage on histology. However, a well defined ring of reduced diffusion was consistently seen and was shown to correspond to the red ring. Diffusion MRI may be more accurate than CE methods in predicting the eventual extent of thermal damage.

                  2545.     Prediction of Long Term Success Rates of MRgFUS for Uterine Fibroids

Yael Inbar1, Ronit Machtinger2, Dahlia Admon2, Boris Khaitovich1, Shlomo Cohen-Eilon2, Jaron Rabinovici2

1Diagnostic Imaging, Sheba Medical Center, Ramat Gan, Israel; 2Obstetrics & Gynecology, Sheba Medical Center, Ramat Gan, Israel

MRgFUS is gaining increased popularity as more women are seeking conservative alternatives for the treatment of uterine fibroids. For this reason it is important to assess the long term outcome of treated patients and to define factors associated with treatment success.

 
Interventional MRI: Devices, Sequences, & Applications
Exhibit Hall 2-3                    Thursday 13:30-15:30

                  2546.     Preliminary Clinical Experience with a Navigation System for Biopsies in a Diagnostic 1.5T Closed-Bore MR Scanner

Michael Moche1, Dirk Zajonz1, Tim-Ole Petersen1, Jochen Fuchs1, Gregor Thörmer1, Nikita Garnov1, Thomas Kahn1, Harald Busse1

1Dept. of Diagnostic and Interventional Radiology, Leipzig University Hospital, Leipzig, Germany

Minimally-invasive MR-guided interventions are becoming increasingly important due to a number of well-known advantages of MRI over other imaging modalities. Over the last years, different concepts for interventional assistance and instrument navigation have been described for practically all regions of the body. This work presents a compact and easily implementable concept for standard cylindrical scanners where the patient is moved out of the bore and the navigation system uses instrument positions that are properly registered to the MR coordinates of 3D anatomical roadmap data. Our preliminary clinical experience from four navigated biopsies in different regions of the body is reported.

                  2547.     Are We Ready for Routine Interventional 1.5 Tesla MRI? Experience from 370 MR-Guided Percutaneous Interventions.

Martin Deli1, Markus Braun2, Serban Mateiescu3, Jan Becker3, Yvonne Maratos3, Martin H J Busch3, Dietrich H W Grönemeyer3

1Amedo GmbH, Bochum, Germany; 2Berufsgenossenschaftliche Unfallklinik Duisburg, Duisburg, Germany; 3Grönemeyer Institut für Mikrotherapie, Bochum, Germany

We performed 370 MR-guided percutaneous interventions at 1.5 Tesla and we would like to share our experiences with the audience.

                  2548.     Immobilization of Breast Tissue Using Small Beads for MR-Guided Breast Interventions

Matthew Smith1, Catherine Moran1, Xu Zhai1, Ray Harter2, Frederick Kelcz3, Sean Fain1,3

1Medical Physics, University of Wisconsin, Madison, WI, USA; 2Marvel Medtech LLC, Madison, WI, USA; 3Radiology, University of Wisconsin, Madison, WI, USA

Biopsy or therapy needles distort the breast upon insertion and cause the internal structures to move, which can shift the target from its original position. Conventional methods of stabilizing the breast during an MR-guided intervention use a planar approach in which the breast is compressed between two parallel stabilization plates, causing the tissue to distort into an unnatural form. We present a novel method that can provide uniform stabilization pressure to the breast surface using small beads. This method preserves the natural breast shape and allows a needle insertion from any angle.

                  2549.     MRI Guided Robotic Assisted Pain Therapy

Andreas Melzer1

1IMSaT, University Dundee, Dundee, Scotland, UK

A fully MR-compatible robotic system was developed to provide precise and reproducible instrument positioning inside the magnet. The Objective was to determine safety and targeting precision during MRI guided percutaneous interventions for pain treatment.

                  2550.     Clinical Use of an Image-Guided Remote Manipulator for Endorectal Prostate Biopsy

Marc A. Rea1,2, Zion Tse2, Veronica Morgan3, Sharon Giles3, Donald W. McRobbie1,3, Michael Lamperth2, Ian Young2, Nandita deSouza3

1Radiological Sciences Unit, Imperial College Healthcare NHS Trust, London, UK; 2Mechanical Engineering, Imperial College London, London, UK; 3MRI, Royal Marsden Hospital, Surrey, London, UK

This work describes clinical trials of a closed-bore 5-DOF remote manipulator used for endorectal prostate biopsy procedures.

                  2551.     Punctures in a Hybrid MR/X-Ray-Angiographysuite Using MR Image Overlay and Stereoscopic X-Ray Navigation: A Study in Phantoms, Animals and a Patient

Bernhard Meyer1, Dara L. Kraitchman2, Alexander Brost3, Liron Yatziv4, Norbert Strobel5, Wesley Gilson6, Jonathan S. Lewin7, Frank K. Wacker7

1Radiology, Charite, Berlin, Germany; 2The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, USA; 3Informatics - Pattern Recognition, Universitaet Erlangen, Erlangen, Germany; 4Siemens Corporate Research, Princeton, NJ, USA; 5AX Division, Siemens Medical Solutions, Forchheim, Germany; 6Siemens Corporate Research, Baltimore, MD, USA; 7The Russell H. Morgan Department of Radiology and Radiological Science , Johns Hopkins University, Baltimore, MD, USA

Purpose: To test the feasibility and accuracy of the stereoscopic X-ray based MR overlay navigation for percutaneous punctures in phantoms, animals and a patient.

                  2552.     X-Ray Fused with Magnetic Resonance (XFM) Applied to Image-Guided Embolization of Venous Malformation in an XMR Suite

Dany Simard1, Sylvain Deschenes2, Josee Dubois2, Gilles Soulez1, Gilles Beaudoin1

1CHUM - Notre-Dame, Montreal, Quebec, Canada; 2CHU Sainte-Justine, Montreal, Quebec, Canada

We developed and validated a method for registration, fusion and display of X-ray fused with MRI (XFM) for an XMR suite. The technique reaches sub-millimetre accuracy through an optimization using information found in DICOM header files and as little as 4 markers. To reach such precision, works from other groups require an optical tracking system or over 15 external multimodality markers. Our display interface can then project and overlay any MR volume onto fluoroscopy images during an intervention. A carotid phantom was used for validation and proof of concept was carried out during embolization of venous malformations.

                  2553.     Biopsy of Liver Lesions with MR Fluoroscopy Using an High Field Open MRI Scanner

Frank Fischbach1, Juergen Bunke2, Markus Thormann1, Gunnar Gaffke1, Jungnickel Kerstin1, Jens Ricke1

1Otto von Guericke University, Magdeburg, SA, Germany; 2Philips Healthcare, Hamburg, HH, Germany

New high field open-configured magnets are best suited for MR-guidance of biopsies in the liver. The technique requires only the basic interventional package and uses a skill set that is already familiar to radiologists who regularly perform percutaneous procedures.

                  2554.     Real-Time MR-Guided Percutaneous Interventions in a Dedicated 1.5T Clinical Suite

Sanaz Javadi1, Roger Jason Stafford2, Judy U. Ahrar1, Sanjay Gupta1, Michael J. Wallace1, Li Pan3, Kamran Ahrar1

1Radiology, University of Texas, MD Anderson Cancer Center, Houston, TX, USA; 2Imaging Physics, University of Texas, MD Anderson Cancer Center, Houston, TX, USA; 3Siemens Corporate Research, Inc, Baltimore, MD, USA

Our initial experience using a dedicated interventional MR suite featuring a 1.5T short bore MR scanner with wide aperture is discussed. We describe our techniques, equipment, imaging and planning protocols as well as results with a focus on our approach to MR-guidance to percutaneous biopsies using real-time imaging (<2s) or intermittent scanning (<6s). We found that using the T2-W and T1-W contrast mechanisms, we could perform procedures without the need for contrast agent.

                  2555.     In Vitro and in Vivo Evaluation of MR Fluoroscopy-Guided Injection Therapy for Low Back Pain in Open High-Field MRI

Florian Streitparth1, Thula Walter2, Jens Rump2, Uta Wonneberger2, Bernd Hamm2, Ulf Teichgräber2

1Radiology, Charité , Berlin, Germany; 2Radiology, Charité, Berlin, Germany

Percutaneous spinal infiltrations are typically performed under CT or conventional fluoroscopy guidance. In this study we evaluated the feasibility of infiltration therapy of the lumbar nerve roots, sacroiliac and facet joints under open high-field MR-guidance (1.0T). In a CuSO4 phantom and cadaveric specimen, interventional TSE and GRE sequences were evaluated according to artifacts and image quality and an optimal intervention angle was assessed. In vivo, we chose a fast PDw turbo spin echo sequence for a total of 141 spinal infiltrations. A strongly T2-w SPIR sequence confirmed successful infiltration. Pain therapy in the open high-field MRI is feasible and safe.

                  2556.     Feasibility of Gd-Enhanced Lymph Node MR Imaging for the Integrated MR Endoscope System

Yuichiro Matsuoka1, Yoshinori Morita1, Hayato Yoshinaka1, Daisuke Obata1, Shoko Fujiwara1, Makiya Matsumoto2, Etsuko Kumamoto3, Hiromu Kutsumi1, Kagayaki Kuroda4, Takeshi Azuma1

1Department of Gastroenterology, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan; 2Graduate School of Engineering, Kobe University, Kobe, Hyogo, Japan; 3Information Science and Technology Center, Kobe University, Kobe, Hyogo, Japan; 4Center for Medical-Facility Clustering, Foundation of Biomedical Research and Innovation, Kobe, Hyogo, Japan

The purpose is to develop an integrated MR-endoscope system. For a new function, the feasibility of lymph node MR imaging with the oligomannose-coated liposome encapsulating Gd and FITC (Gd-FITC-OML) was examined with an in vivo animal experiment. In addition, a flexible intragastric RF coil was designed to create 3-dimensional stomach image. As a result, the Gd-enhanced neck lymph node was visualized after the Gd-FITC-OML injection. Furthermore, 3-dimensional image visualizing stomach with outer region was created, which would be able to identify the lymph node near the stomach. Therefore, the feasibility of lymph node imaging by this system was indicated.

                  2557.     Real Time MRI for Guidance of Electrophysiological Interventions Using Carbon Catheters

Peter Nordbeck1,2, Oliver Ritter1, Florian Fidler3, Marcus Warmuth2, Karl-Heinz Hiller3, Matthias Nahrendorf4, Michelle Maxfield5, Sabine Wurtz5, Wolfgang Geistert5, Peter M. Jakob2, Wolfgang R. Bauer1

1Medizinische Klinik I, Universität Würzburg, Würzburg, Germany; 2Experimentelle Physik V, Universität Würzburg, Würzburg, Germany; 3Forschungszentrum MRB, Würzburg, Germany; 4Center for Molecular Imaging Research, Harvard Medical School, Boston, USA; 5Biotronik GmbH & Co. KG, Berlin, Germany

MRI has been proposed a beneficial imaging modality for investigations and interventions in clinical electrophysiology (EP). Recently, first successful diagnostic EP investigations under real time MRI guidance have been reported. In the current work, a custom setup including MR conditional catheters was used to perform interventional EP studies in a porcine model under real time MRI guidance, including initial experiments of post-procedural lesion mapping.

                  2558.     Transcatheter Intraarterial Perfusion (TRIP)-MRI Monitoring of Uterine Fibroid Embolization in VX2 Rabbits

Dingxin Wang1, Robert Ryu2, Johnathan Chung2, Richard Tang2, Rachel Klein2, Barbara Szolc-Kowalska3, Gayle Woloschak3,4, Reed Omary1,4, Andrew Larson1,4

1Departments of Radiology and Biomedical Engineering, Northwestern University, Chicago, IL, USA; 2Department of Radiology, Northwestern University, Chicago, IL, USA; 3Radiation Oncology, Northwestern University, Chicago, IL, USA; 4Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, IL, USA

Proper selection of UAE endpoints is critical because under-embolization may cause incomplete treatment and over-embolization may harm normal uterine tissue and generate excessive post-procedural ischemic pain. TRanscatheter Intraarterial Perfusion (TRIP)-MRI (involving catheter-directed intraarterial contrast injections) has been demonstrated to permit intra-procedural measurement of tumor perfusion changes during liver-directed embolo-therapies. As a step towards determining the optimal endpoint for UAE, we tested the hypothesis that TRIP-MRI can measure uterine fibroid perfusion reductions during UAE in a rabbit VX2 uterine tumor model. TRIP-MRI can be used to objectively measure uterine fibroid perfusion reduction after UAE in a rabbit uterine tumor model.

                  2559.     Diffusion-Weighted PROPELLER MRI for Tissue Selective Intra-Procedural Positioning of Percutaneous Biopsy Needles Within Rabbit VX2 Liver Tumors

Jie Deng1,2, Sumeet Virmani1, Richard A. Tang1, Guang-Yu Yang3, Gayle Woloschak1,4, Reed A. Omary1,5, Andrew C. Larson1,5

1Department of Radiology, Northwestern University, Chicago, IL, USA; 2Department of Medical Imaging, Children's Memorial Hospital, Chicago, IL, USA; 3Feinberg School of Medicine, Northwestern University, Chicago, IL, USA; 4Department of Cell and Molecular Biology, Northwestern University, Chicago, IL, USA; 5Robert H. Lurie Comprehensive Cancer Center , Northwestern University, Chicago, IL, USA

MRI can be used for intra-procedural guidance during percutaneous liver-directed interventions. Optimal targeting of viable tumor tissues is critical during biopsy procedures for accurate histological confirmation of malignancy. Diffusion-weighted (DW) MRI can be employed for in vivo differentiation between viable tumor tissues and tumor. TSE-based DW-PROPELLER techniques should be less sensitive to susceptibility-induced field inhomogeneities near interventional devices. We demonstrated the feasibility of using DW-PROPELLER MRI to guide biopsy needle placement to selectively target viable tissues within VX2 rabbit liver tumors. DW-PROPELLER is a promising method to optimize placement of percutaneous devices during interventional procedures.

                  2560.     Towards Fully MR-Guided TACE Procedures: Perfusion MRI and Real-Time MRA Protocols

Michael Bock1, Ann-Kathrin Homagk1, Axel Krafft1, Florian Maier1, Jessica Schulz1,2, Reiner Umathum1, Wolfhard Semmler1, Peter Hallscheidt3

1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany; 2Siemens AG, Healthcare Sector, Erlangen, Germany; 3Dept. of Radiology, University Heidelberg, Heidelberg, Germany

In this work a real-time saturation recovery pulse sequence is used to monitor a superselective hepatic embolisation. To assess embolisation-induced perfusion changes, time-resolved FLASH data sets are acquired before and after the embolisation. Compared to conventional MR-guided embolisation in X/MR-suites this procedure does not require patient re-psoitioning and is thus significantly faster.

                  2561.     MR Validation and Quantification of TACE Treatment Through Direct Visualization of Ethiodol with Chemical Shift Based Water-Fat Imaging

Eric M. Bultman1, Catherine D. Hines1, Walter F. Block1,2, Scott B. Reeder1,3

1Department of Biomedical Engineering, University of Wisconsin, Madison, WI, USA; 2Department of Medical Physics, University of Wisconsin, Madison, WI, USA; 3Department of Radiology, University of Wisconsin, Madison, WI, USA

Transcatheter arterial chemoembolization is frequently used to treat unresectable malignant neoplasms of the liver such as HCC. Traditionally, TACE delivers a bolus of chemotheraputic agents, suspended in ethiodol, through a hepatic arterial catheter. In this work, we explore the feasibility of using IDEAL fat-water separation to exploit the fat-based contrast provided by ethiodol, allowing for visualization of the region of TACE treatment via MR imaging. Results demonstrate the equivalence of IDEAL fat-only imaging to follow-up CT scan with regards to quality of visualization, while the IDEAL fat fraction may allow for monitoring of ethiodol dose delivery during the procedure.

                  2562.     19F MR-Visualization of Fluoropolymers Using Ultrashort TE Imaging

Jürgen Rahmer1, Jochen Keupp1

1Philips Research Europe, Hamburg, Germany

19F ultrashort echo-time (UTE) imaging for the first time allows MR visualization of fluoropolymers such as PTFE

                  2563.     In-Vivo Evaluation of an Active Filter System for the ICV Using MRI

Nils A. Kraemer1, Erwin Immel2,3, Andreas Melzer2, Christina Ocklenburg4, Rolf W. Guenther1, Gabriele A. Krombach1, Elmar Spüntrup5

1Diagnostic Radiology, University Hospital Aachen, Aachen, Germany; 2BIOPHAN Europe GmbH, Germany; 3IMSat, Institute for Medical Sciences and Technology, University of Dundee, UK; 4Institute for Medical Statistics, Universiy Hospital Aachen, Aachen, Germany; 5Diagnostic and Interventional Radiology, University Clinic Cologne, Germany

Aim of the study is to evaluate the function and MRI characteristics of an active filter system for the inferior caval vein (ICV) in a swine model. Solely using real-time MRI guidance, the filter was deployed in the ICV. The built-in resonator significantly enhances the signal inside the filter depending on the flip angle and other sequence characteristics. All venous thrombi were filtered effectively. The active components improved filter deployment and facilitated a clear depiction of intra-filter thrombi using MRI, which were verified through autopsy.

                  2564.     Hybrid Tracking and Visualization of Therapeutic Devices Under MRI Guidance

Orhan Unal1,2, Ethan K. Brodsky1, Krishna N. Kurpad2

1Department of Medical Physics, University of Wisconsin, Madison, WI, USA; 2Department of Radiology, University of Wisconsin, Madison, WI, USA

The objective of this study was to perform in vitro and in vivo evaluation of hybrid devices that utilize mr-visible coatings for passive visualization of the entire length of a device, miniature RF-coils for accurate active tracking of the tip of a device tip, and inductively coupled self-resonators (wireless markers) to further improve passive visualization therapeutic devices such as catheters.

                  2565.     The Interventioal Device Tracking Using Miniaturized Micro Coils

Sunil Patil1, Jens Anders2, Reiner Umathum3, Michael Bock3, Giovanni Boero2, Klaus Scheffler1

1Division of Radiological Physics, University of Basel Hospital, Basel, Switzerland; 2Laboratoire de Microsystèmes, Ecole Polytechnique federele de Lausanne, Lausanne, Switzerland; 3Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany

Currently available active coils that are used to track the interventional devices are bulky in nature. In order to overcome this disadvantage, in this work, highly miniaturized micro-coils with typical dimensions of 500μm X 500μm and built-in low noise amplifier are being developed and designed to operate at 1.5T clinical scanner. The feasibility phantom experiments demonstrates its ability as a RF detector.

                  2566.     An Expandable Catheter Loop Coil for Intravascular MRI in Larger Blood Vessels

Ann-Kathrin Homagk1, Reiner Umathum1, Matthias Korn1, Marc-André Weber2, Peter Hallscheidt2, Wolfhard Semmler1, Michael Bock1

1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; 2Diagnostic and Interventional Radiology, University Hospital, Heidelberg, Germany

The present study proposes a catheter system with an expandable coil which combines the advantages of a small insertion diameter and an increased SNR and penetration depth due to the expanded coil surface. The catheter system was tested on two healthy anesthetized pigs. The images acquired during the expansion of the coil revealed the expected higher signal intensity once the coil was expanded. For high-resolution intravascular imaging, a flow-compensated 2D FLASH sequence with the acquisition of projection data for retrospective gating was implemented. The experiments demonstrated the capability of this catheter design for tracking and high-resolution vessel wall imaging.

                  2567.     Comparative Evaluation of the Geometrical Accuracy of Intravascular MRI

Guillaume Gilbert1, Gilles Soulez1, Gilles Beaudoin1

1Department of Radiology, Centre Hospitalier de l'Université de Montréal, Montreal, Quebec, Canada

In this abstract, the geometrical accuracy of intravascular MRI is evaluated in the context of vascular morphological measurements and compared with results obtained using intravascular ultrasound (IVUS) and surface MRI. Measurements are performed on a multimodality vascular phantom and several bSSFP sequence parameters are investigated in order to assess their influence. Using IVUS as a gold standard, intravascular MRI is shown to lead to an increase in geometrical accuracy in comparison to surface MRI. It also appears that sequence parameters should be tailored to vessel size and procedural time constraints.

                  2568.     Transmit Power Optimization for Multimode Coil

Krishna N. Kurpad1, Erik T. Bieging2, Ethan K. Brodsky1,3, Orhan Unal3

1Radiology, University of Wisconsin - Madison, Madison, WI, USA; 2Biomedical Engineering, University of Wisconsin - Madison, Madison, WI, USA; 3Medical Physics, University of Wisconsin - Madison, Madison, WI, USA

 

                  2569.     Active Visualization of MR-Compatible Guidewires

Kevan James Thompson Anderson1, Graham A. Wright1,2

1Medical Biophysics, University of Toronto, Toronto, Ontario, Canada; 2Imaging Research, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada

Safety concerns exist regarding the use of conventional guidewires in an MR scanner. Recently, an MR-compatible guidewire design has been evaluated but visualization is limited to passive techniques. In this study, a method is presented for actively visualizing the conducting segment of an MR-compatible guidewire by magnetically coupling it to a pick-up coil located inside a guide catheter. In contrast to conventional active guidewires, the approach incorporates signal reception into the catheter rather than the guidewire to avoid the size constraints that limit the use of safety features.

                  2570.     In-Stent Lumen Visualization Using Intravascular MRI and a BSSFP Sequence

Guillaume Gilbert1, Gilles Soulez1, Gilles Beaudoin1

1Department of Radiology, Centre Hospitalier de l'Université de Montréal, Montreal, Quebec, Canada

In this abstract, the use of an intravascular loopless antenna is investigated as a way to reduce radiofrequency shielding for an improved visualization of the vessel lumen inside a metallic vascular stent. Measurements are performed on a dedicated vascular phantom using a bSSFP sequence. In comparison to traditional surface MRI, the use of the intravascular antenna is shown to lead to an improved lumen visualization as a result of the intrinsically higher sensitivity of the intravascular antenna and a reduction of the radiofrequency shielding of the stent during signal reception.

                  2571.     Visualization and Tracking of a Conventional Guidewire with Low Flip Angle SSFP Imaging: An Initial Study

Rohan Dharmakumar1, Ioannis Koktzoglou2, Sotirios A. Tsaftaris3, Sven Zuehlsdorff4, Richard A. Tang1, Graham A. Wright5, Debiao Li1

1Radiology, Northwestern University, Chicago, IL, USA; 2Radiology, NorthShore University HealthSystem, Evanston, IL, USA; 3Electrical Engineering and Computer Science, Northwestern University, Evanston, IL, USA; 4Siemens Healthcare, Chicago, IL, USA; 5Medical Biophysics, University of Toronto, Toronto, ON, Canada

Inductive coupling between signal reception coils and conventional guidewires in the presence of low flip-angle (LF) balanced SSFP (b-SSFP) imaging may permit the visualization of guidewires with positive contrast. To test our hypothesis, ex-vivo and in-vivo experiments were performed using a radio-opaque coronary guidewire and LF b-SSFP imaging. Our initial studies showed that it is possible to visualize and track a conventional guidewire with positive contrast using LF b-SSFP imaging within ex-vivo and in-vivo settings. These results lend support to the hypothesis that signal reception coils and passive guidewires may be inductively coupled in the presence of LF excitations.

                  2572.     RF Safe Interactive Catheter Tracking with Variable DC-Susceptibilty Artefacts

Jens Pinkernelle1, Anja Wagner1, Jens Rump1, Ulf KM Teichgräber1

1Diagnostic and Interventional Radiology, Charité - University Medicine, Berlin, Germany

MR guided vascular interventions require reliable and safe catheter tracking methods. Direct currents produce susceptibility artefacts in MRI which can be adjusted dependent on the current applied. In this study a high frequency safe method of direct current based catheter tracking in interventional MRI is presented ready to be introduced in clinical routine. It is based on a miniaturized optoelectric circuit allowing building a vascular catheters prototype which diameter does not exceed 7F.

                  2573.     Fast, Robust 3D Visualization and Automatic Slice Repositioning (“Snap-To”) for MR-Guided Interventions Using Active Device “Profiling”

Ashvin George1, Christina Saikus1, John Andrew Derbyshire1, Anthony Z. Faranesh1, Ozgur Kocaturk1, Robert J. Lederman1, Michael Guttman1, Elliot R. McVeigh2

1National Institutes of Health, Bethesda, MD, USA; 2Johns Hopkins University, USA

In MR-guided interventional procedures it is important to be able to quickly and automatically re-position the imaging slices to contain the active device in order to safely guide the procedure. Manual repositioning of the slice is time-consuming and inaccurate. We present a method that computes a parameterization of the active device from sparse 2D projection images. The parameterization is used to calculate the slice position and improve visualization of the device. It can be used for a variety of active devices and the imaged slice(s) can be located at specific segments of the device.

                  2574.     Multi-Phase 3D Angiography Roadmaps for Real-Time MRI-Guided Procedures

Haris Saybasili1,2, Anthony Z. Faranesh1, Christina E. Saikus1, Cengizhan Ozturk2, Robert J. Lederman1, Michael A. Guttman1

1Translational Medicine Branch National Heart Lung Blood Institute, National Institutes of Health, Bethesda, MD, USA; 2Institute of Biomedical Engineering, Bogazici University, Istanbul, Turkey

We present a new software system that creates colored MIPs in real-time using pre-acquired MRA and MRCP data, and that allows us to render and to display dynamically these 3D MIPs with different colors interactively in real-time, by alpha-blending them with real-time reconstructed multi-slice images. The colorization improves the visibility of the vascular structures and will help to identify the orientation and the location of devices in real-time during MRI guided procedures, such as TIPS, angioplasty, biopsy, stent placement, and electrophysiology applications. Our software has the potential of improving patient safety and procedure efficacy for MRI-guided interventional applications.

                  2575.     Development of a Training Model for PTCD Under MRI Real-Time Guidance (MRI-PTCD)

Ivo Raymond van der Voort1, Ioannis S. Papanikolaou1, Jens Rump2, Christian Seebauer2, René Schilling2, Sascha Chopra2, Bertram Wiedenmann1, Ulf Teichgräber2, Thomas Rosch1

1Department of Hepatology and Gastroenterology, Charité Universitätsmedizin Berlin, CVK, Berlin, Germany; 2Research Group for Engineering Instruments for the open MRI, Charité Universitätsmedizin Berlin, Berlin, Germany

The aim was to establish a training model for MRI-PTCD and to compare procedure times of MRI and conventional radio¬logic guided PTCD. An in-vitro model was used in an open-MRI-scanner 1.0 Tesla. The success rates, puncture time by MR-guidance and by conventional methods using the same model, and learning curve were calculated. The successful puncture rate in the oMRI group was significantly higher, puncture time shorter. The learning curve of MRI-PTCD showed a shorting in puncture time for the last 15 punctures. Initial in-vitro experience shows that PTCD can be successfully and ra¬pid¬ly performed under real-time-MRI-guidance and can also be used for training.

                  2576.     MR-Compatible Wireless Communication System for the Interventional Open High-Field MRI

Felix Victor Guettler1, Jens Christian Rump1, Ulf Teichgraeber1

1Radiology, Charite, Berlin, Germany

In a MRI-guided intervention, unobstructed communication between the medical personal and the interventionalist is crucial. A special hurdle to overcome is the high level of noise during image acquisition, which is caused by gradient coils during image acquisition. Therefore two speech activated Bluetooth headset prototypes were developed and analyzed in high-field MRI. MR-safety could be established according to ASTM. No loss of SNR of MR imaging was found. The manageability and practicability in interventional scenarios were verified in clinical tests. The herein presented communication system is a practicable and flexible alternative to existing solutions.

 
RF Pulse Design
Exhibit Hall 2-3                    Monday 14:00-16:00

                  2577.     Reduced Peak Power Dualband VSS Pulse Design

Adam B. Kerr1, Peder E. Z. Larson2, Daniel B. Vigneron2, John M. Pauly1

1Electrical Engineering, Stanford Univers ity, Stanford, CA, USA; 2Radiology and Biomedical Imaging, UCSF, San Francisco, CA, USA

An efficient method for designing a reduced peak power dualband VSS pulse for application to clinical MRSI studies is presented. The approach is appropriate for incorporation during scan prescription which will allow for variable specification of band thickness, separation and tip-angle. The peak RF amplitude of the design is only 1.4 times that of a peak-power reduced single-band VSS pulse.

                  2578.     Numerical Optimization of Minimum Phase RF Pulses for UTE Imaging

Andrew T. Curtis1,2, Christopher K. Anand3, Craig K. Jones1, L Martyn Klassen1, Ravi S. Menon1,2

1Center for Functional and Metabolic Mapping, Robarts Research Institute, London, Ontario, Canada; 2Medical Biophysics, University of Western Ontario, London, Ontario, Canada; 3Computing and Software, McMaster University, Hamilton, Ontario, Canada

A numerical optimization method for radiofrequency (RF) pulse design for Ultra-short TE (UTE) imaging was designed. Pulses are designed to play out over the ramp-down of the slice select gradient, and are nearly self-rewound – requiring no slice select rewinder. This is a gain versus typical slice based, ‘half-RF’ UTE methods where double the number of acquisitions are required to perform proper slice selection. The generated pulses have good profiles over the designed field-of-view (FOV), and have moderate power requirements. Preliminary images of a short-T2 phantom are showcased.

                  2579.     A Novel Radiofrequency Pulse Design for Improving Flip-Angle Uniformity in Ultra-High Field MRI

Jason E. Moore1, Marcin Jankiewicz1,2, Huairen Zeng1,2, Adam W. Anderson1,3, Malcolm J. Avison1,3, E Brian Welch1,4, John C. Gore1,3

1Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA; 2Department of Radiology, Vanderbilt University; 3Department of Biomedical Engineering, Vanderbilt University; 4Philips Healthcare, Cleveland, OH, USA

A pulse design method involving a composite of numerous block pulses with amplitude and phases subject to numerical optimization is introduced with the goal of achieving a uniform flip angle distribution across a wide range of field strengths. Possible applications include B1+ insensitive excitation and refocusing at ultra-high field.

                  2580.     Compensation of the Susceptibility Artifact in Temporal and Orbitofrontal Region in Brain Using the Flat RF Pulse

Sung Suk Oh1, Sungdae Yun1, HyunWook Park1,2

1Department of Electrical Engineering, KAIST, Daejeon, Korea; 2fMRI Laboratory of Brain Research Center, KAIST, Daejeon, Korea

The susceptibility artifact in magnetic resonance (MR) image occurs by the variation in the magnetic field strength around the interface of substances having different magnetic susceptibility. Especially, this artifact has an effect on the signal loss on orbitofrontal and temporal regions of the brain. For the compensation of this artifact, we propose a new RF pulse having bilinear phase, and quadrature phase, which provides nearly constant signal intensity against the magnetic susceptibility.

                  2581.     Maximizing T2 Signal Weighting Generated by RF Excitation

Michael Carl1, Mark Bydder2, Atsushi Takahashi1, Eric Han1, Graeme Bydder2

1GE Healthcare, Applied Science Lab, Milwaukee, WI, USA; 2Radiology, University of California, San Diego, CA, USA

Traditionally, T2 weighting in MR is controlled by varying the sequence echo time (TE). Alternatively, T2 contrast can be generated from the RF pulse itself. Using theoretical calculations and Bloch simulations we study ways to maximize T2 weighting generated by this mechanism. It is shown that the pulse duration is the primary means to adjust the peak of the T2 weighting function toward the tissues of interest.

                  2582.     Image Contrast Enhancement Using Selective Adiabatic Pulses That Alternate Frequency Sweep Directions

Ziqi Sun1, Robert Bartha2,3, Hanna A. Park1, Surya Gnyawali1

1Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA; 2Imaging Research Laboratories, Roberts Research Institute, London, Ontario, Canada; 3Departments of Diagnostic Radiology and Medical Biophysics, University of Western Ontario, London, Ontario, Canada

Image contrast enhancements were observed both in a multi-compartments phantom and in a stroke mouse model using a customized spin echo (SE) pulse sequence incorporated with selective adiabatic full passage (AFP) pulse trains that alternate frequency sweep (AFS) directions between adjacent pulses. Bloch equation simulation indicated that paired AFP-AFS pulse trains generated more accurate spin refocusing and thus signal intensity (SI) than that of the paired AFP pulses using single frequency sweep (SFS) in the pulse train. The accumulated nonlinear phase dispersion produced by the AFP-AFS pulse train also contributed to the contrast enhancement at longer TE.

                  2583.     Tailored Saturation Pulses for Abdominal Imaging at 3 Tesla

Houchun Harry Hu1, Kyunghyun Sung2, Krishna S. Nayak1

1Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, CA, USA; 2Department of Radiology, Stanford University, Stanford, CA, USA

Robust saturation of longitudinal magnetization is necessary for many abdominal imaging applications such as dynamic contrast enhanced imaging to maximize contrast-to-noise ratio, renal arterial spin labeling to suppress background signals, and RF transmit (B1+) mapping with the saturated double-angle-method. This work demonstrates the design of tailored RF saturation hard-pulse trains that are appropriate for addressing the large B0 and B1+ variations that exist across the human abdomen at 3 Tesla. We show that trains consisting of three to five hard pulses with varying sub-pulse areas provide more uniform saturation than adiabatic BIR-4 pulses and constant-area 90° hard pulse trains.

                  2584.     Tailored Shaping and Time Resampling Functions for Inversion Pulses at 7T

Aaron Christopher Hurley1,2, Ron Coxon2, Ali Al-Radaideh2, Uwe Aickelin1, Li Bai1, Penny Gowland2

1Computer Science, University of Nottingham, Nottingham, UK; 2SPMMRC, University of Nottingham, Nottingham, UK

The RF transmit field is severely inhomogeneous at ultrahigh field, due to both RF penetration and RF coil design issues. Here we utilised a search algorithm to produce inversion pulses tailored to take account of the heterogeneity of the RF transmit field at 7T. We created a slice selective inversion pulse which worked well over the range of RF amplitudes, while maintaining an experimentally achievable pulse length at 7T. The pulses were based on the FOCI technique as well as time dilation of functions but the RF amplitude, frequency sweep and gradient functions were all optimised using a Genetic Algorithm.

                  2585.     In Vivo RF Power and SAR Calibration for Multi-Port RF Transmission

Yudong Zhu1

1New York University Langone Medical Center, New York, USA

To better manage SAR in parallel RF transmission one must complement real-time monitoring with a more proactive scheme. In principle, for RF pulse design one can explicitly minimize SAR by guiding the design with a predictive SAR model. In this work we developed a practical method that is capable of establishing such a model under in vivo imaging conditions. The model predicts, for any set of RF pulse waveforms or shimming coefficients, the overall SAR of the multi-port operation. A connection with an established multi-port system theory as well as preliminary experimental data offered a validation for the method.

                  2586.     Effects of Relaxation During RF Pulses on the Homogeneity of Signal Intensity in Parallel Transmission

Masaki Sekino1,2, Nicolas Boulant1, Michel Luong3, Alexis Amadon1, Hiroyuki Ohsaki2, Denis Le Bihan1

1CEA, DSV, I2BM, NeuroSpin, Gif-sur-Yvette, France; 2Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan; 3CEA, Irfu, SACM, Gif-sur-Yvette, France

Dynamic RF shimming techniques in combination with parallel transmission have been uniquely based on the spinsf coherent dynamics, and do not account for relaxation during the RF pulses. We numerically investigated at 7 T the degradation of the spoiled gradient echo signal homogeneity when designing a transmit-SENSE pulse aimed at homogenizing the flip angle over an axial slice of a human head. Although the final uniformity may still be very good, we show that the signal inhomogeneity can sometimes deteriorate by a factor of 10 because of relaxation and should worsen even more at higher fields. The effect seems mostly noticeable around the Ernst flip angle.

                  2587.     Correction of B0 Induced Slice Profile Distortion Using Parallel Transmit

Shaihan J. Malik1, David J. Larkman1, Jason Filos1, Jo V. Hajnal1

1Imaging Sciences Department, Hammersmith hospital, Imperial College London, London, UK

Off-resonance effects can lead to geometric distortion of slice profiles at higher fields, which often goes unnoticed. We explored the problem at 3T using a system equipped with an 8-channel parallel transmission body coil. It is demonstrated that a slab selective excitation which is noticeably bent can be straightened by use of tailored pulses without changing the gradient trajectory, opening up the possibility that such a correction can be made an add-on to standard sequences.

                  2588.     Compensation of Concomitant Maxwell Gradient Effects in 3D Multi-Element Spatially Selective RF Excitation

Tim Nielsen1, Peter Börnert1, Ulrich Katscher1, Ingmar Graesslin1

1Philips Research Europe, Hamburg, Germany

Parallel RF excitation using multi-element transmit coils is of interest to reduce pulse duration for spatially selective excitation. Here, we extend RF pulse calculation methods to compensate for the effects of concomitant Maxwell gradients. Their influence on the performance of 3D spatially selective excitation at a main field strength of 3T is investigated for a stack of spirals trajectory and different sizes of the field of excitation. To achieve high excitation quality, it is important to compensate the effect of concomitant gradients for a large field of excitation and long pulse duration mainly found in 3D RF applications.

                  2589.     T2*-Compensated Transmit SENSE RF Pulses

Martin Haas1, Denis Kokorin1, Peter Ullmann2, Johannes T. Schneider2, Jürgen Hennig1, Maxim Zaitsev1

1Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany; 2Bruker BioSpin MRI GmbH, Ettlingen, Germany

Long multidimensionally selective RF pulses suffer from main field offresonances and from relaxation taking place during the RF transmission. Parallel transmit techniques can reduce these problems by shortening the total duration of the pulses. In addition, algorithms that account for offresonances in the pulse design have been demonstrated. In this work a parallel transmit RF design method is presented for creating pulses that are inherently compensated for transverse relaxation (T2*). The presented algorithm can be understood as a generalization of existing offresonance correction schemes into the complex domain.

                  2590.     Time-Optimal VERSE for Multidimensional and Parallel Excitation

Daeho Lee1, Michael Lustig1, William Allyn Grissom1, John Mark Pauly1

1Electrical Engineering, Stanford University, Stanford, CA, USA

Variable-rate selective excitation (VERSE) is a RF pulse reshaping technique. It is commonly used to reduce the peak magnitude and SAR of a RF pulse by reshaping RF and gradient waveforms to reduce RF magnitude while preserving the excitation profile. A general time-optimal VERSE algorithm for multidimensional and parallel excitation pulses is presented. This method is different from other VERSE techniques in that it provides a non-iterative time-optimal multidimensional solution, which drastically simplifies VERSE designs. Compared to other parallel excitation SAR-reduction strategies, the algorithm is trajectory-independent and allows the user to design pulses without enforcing RF constraints or making excitation error tradeoffs, and to subsequently obtain the shortest pulses possible that satisfy RF and gradient limits.

                  2591.     Implementation of VERSE Parallel Transmission at 9.4 T

Xiaoping Wu1, J. Thomas Vaughan1, Kâmil Ugurbil1, Pierre-François Van de Moortele1

1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA

Parallel Transmission (PT) has been suggested as an effective tool for addressing Transmit (Tx) B1 inhomogeneity at high magnetic fields. However shorter selective RF pulses obtained with PT acceleration typically require higher RF amplitudes, resulting in increased levels of Specific Absorption Rate (SAR) which may raise concerns for patient safety. A previous simulation study has shown that an efficient way of reducing SAR in PT is to apply the Variable Rate Selective Excitation (VERSE) principle in RF pulse design, which proves to be more effective in decreasing SAR than just linearly increasing RF pulse duration. In the present study, we verify experimentally the method proposed in by conducting VERSE-PT experiments at 9.4 T.

                  2592.     Parallel Transmit Pulse Design Through "Learning"

Yudong Zhu1

1New York University Langone Medical Center, New York, USA

Validation results obtained with simulations are presented and discussed.

                  2593.     Minimal-SAR RF Pulse Optimization in Parallel Transmission

Yinan Liu1,2, Jim Ji1

1Texas A&M University, College Station, TX, USA; 2GE Healthcare Coil, Aurora, OH, USA

Parallel transmission is an emerging technique to achieve multi-dimensional spatially selective excitation from multiple channels. Minimizing SAR is a critical issue for parallel transmission. In this paper, we presented an automatic method to obtain the minimal SAR by optimizing the k-space trajectory in a Lagrange function. The method is verified using computer simulations of a 4-channel parallel transmission system. The results showed significant reduction in SAR can be achieved without enlonging the pulse duration.

                  2594.     Sparse Spokes Pulse Design and B1+ Inhomogeneities in Ultra-High Field MRI

Marcin Jankiewicz1, Jason E. Moore1, Huairen Zeng1, Adam W. Anderson1, E. Brian Welch1,2, Malcolm J. Avison1, John C. Gore1

1Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA; 2Philips Healthcare, Clevelend, OH

We investigate sparse-spokes pulse, designed for mitigation of B1+ inhomogeneities in ultra-high field MRI.

                  2595.     Fast Selection of Phase Encoding Locations in Parallel Excitation

Daehyun Yoon1, Ray Maleh2, Anna C. Gilbert2, Jeffrey A. Fessler1, Douglas C. Noll3

1Electrical Engineering, University of Michigan, Ann Arbor, MI, USA; 2Mathematics, University of Michigan, Ann Arbor, MI, USA; 3Biomedical engineering, University of Michigan, Ann Arbor, MI, USA

We propose a novel, fast method based on a hybrid version of Simultaneous Orthogonal Matching Pursuit(S-OMP) to select sparse phase-encoding locations in a Echo-Volumar(EV) trajectory for parallel excitation pulse design with slice-selective subpulses. Sparse phase-encoding selection was previously presented as a convex optimization problem in a Second Order Cone Program(SOCP) form, which was too slow to be computed on-line in parallel excitation. We present a much faster greedy algorithm, Parallel-OMP(P-OMP), which will solve the same problem in a few seconds with compatible accuracy to that of SOCP in both the single and multiple coil cases.

                  2596.     Sparse Selective Excitation Pulse Design Using Adaptive Energy Threshold Method

Dong Chen1,2, Folkmar Bornemann1, Mika W. Vogel2, Yudong Zhu3

1Center for Mathematical Sciences, Technical University of Munich, Munich, Germany; 2Imaging Technologies, GE Global Research Europe, Munich, Germany; 3New York University Langone Medical Center, New York, NY, USA

Conventional 2D target excitation RF pulse design uses pre-determined k-trajectory based on the k positions required by Nyquist theorem. However Nyquist theorem is sufficient but not necessary condition for most practical target profile. Unlike the spatial encoding task in imaging, where the underlying image is unknown, in the case of excitation pulse design the target excitation profile is known a priori. In this work we propose a k space sparsifying method that exploits this prior-knowledge using Adaptive Energy-Threshold, which significantly reduces pulse duration and offers flexible tradeoff between excitation quality and pulse duration. The method was validated in phantom imaging experiments.

                  2597.     Designing RF Refocusing Pulses for Parallel Transmit Spin Echo Sequences

Dan Xu1, Kevin F. King1

1Applied Science Laboratory, GE Healthcare, Waukesha, WI, USA

Most existing applications of parallel transmission have been restricted to gradient echo due to lack of systematic design of parallel transmit refocusing pulses. In this paper, we propose a new optimal control based method to design parallel transmit refocusing pulses for spin echo sequences with a single refocusing pulse per repetition time. The method addresses pulse nonlinearity by including Bloch equation in the formulation, designs pulses that refocus a spin ensemble, and optimizes nutation directions to achieve homogenous refocusing. Simulation results show that refocusing pulses designed by the proposed method produce better homogeneity than pulses designed by conventional methods.

                  2598.     Two Dimensional Spatial Selective Shinnar Le Roux Pulse Design for Arbitrary k-Space Trajectory

Yong Pang1, Gary Xiong Shen2, Xiaoliang Zhang1

1Radiology&Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA; 2MRI lab, Electrical & Electronic Engineering, University of Hong Kong, Hong Kong

In this work, the Shinnar Le Roux method is extended to design two dimensional RF pulse on arbitrary k-space trajectory. The 2D filter coefficients are designed using McClellan transformation firstly; And then, the inverse gridding algorithm is applied to resample the 2D filter coefficients in Cartesian trajectory to arbitrary k-space trajectory needed; Finally, the SLR inverse transform is applied to convert these filter coefficients to a 2D RF pulse. Simulation results of a 90° excitation pulse design on spiral trajectory shows that the in-slice error, out-of-slice error and the transition can be traded off using our proposed method.

                  2599.     A Dual Fly-Back Spectral-Spatial RF Pulse for Lipid Suppression and Reduced Susceptibility Artifacts

Weiran Deng1, Cungeng Yang1, V A. Stenger1

1University of Hawaii JABSOM, Honolulu, HI, USA

A fly-back dual-band spectral-spatial RF pulse for simultaneous lipid suppression and B0 inhomogeneity correction is presented. This pulse provides a simple and analytical alternative to previously proposed numerical solutions. The improvement is shown with in vivo structural and functional MRI data.

                  2600.     SAR Reduction in Parallel Transmission by K-Space Dependent RF Pulse Selection

Peter Börnert1, Julia Weller2, Ingmar Graesslin1

1Philips Research Europe, Hamburg, Germany; 2University Hamburg, Hamburg, Germany

In this work an alternative concept for SAR reduction in parallel transmission is proposed. Core element of this approach is the idea that different areas in the sampling k-space show different sensitivities to signal imperfections. Thus, instead of using a single and fixed RF pulse for image acquisition, different RF pulses are used in a k-space dependent manner. Each of these RF pulses might show a different performance resulting in a different SAR value. The average SAR over such a single scan can thus be reduced compared to the use of a fixed RF pulse without scarifying significant image quality.

                  2601.     Enhanced Image Resolution and Reduced Measurement Time Using Inner Volume Imaging and Parallel Excitation

Johannes Thomas Schneider1,2, Martin Haas2, Jürgen Hennig2, Sven Junge1, Wolfgang Ruhm1, Peter Ullmann1

1Bruker BioSpin MRI GmbH, Ettlingen, Germany; 2Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany

With parallel transmission / TransmitSENSE arbitrarily shaped regions can be selectively excited with reasonable pulse durations which allows inner volume imaging by reduction of the field of view (FOV) to excited regions of interest. The achievable FOV reduction factor is limited by decreasing SNR and by potentially backfolded residual signals resulting in aliasing artifacts, which both is assessed in the present study. FOV reduction by a factor of 4 in each direction was applied successfully to imaging of a phantom, a kiwi and a rat in-vivo. Reduction of measurement time and enhanced image resolution by the same factor were achieved.

                  2602.     Single- And Multi-Voxel MR-Spectroscopy Using Parallel Excitation

Peter Ullmann1, Johannes Thomas Schneider1,2, Martin Haas2, Ralph Wissmann1, Wolfgang Ruhm1

1Bruker BioSpin MRI GmbH, Ettlingen, Germany; 2Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany

Spatially-selective excitation (SSE) offers great potential for volume-selective MR-spectroscopy (MRS) by allowing the simultaneous excitation of multiple arbitrarily-shaped voxels which can be used to mitigate partial-volume effects and to increase SNR. With Parallel Excitation (PEX) the usability of SSE for MRS can be significantly enhanced due to the reduced durations and the improved spatial and spectral characteristics of the excitation pulses. In the present study the feasibility of PEX-based MRS is demonstrated by performing single- and simultaneous multi-voxel spectroscopic acquisition in a simple two-component sample using dual-band PEX-pulses.

                  2603.     MR Spectroscopy of Arbitrarily Shaped Single Voxel Using Half-Fourier 2D-Selective RF Excitations Based on a PROPELLER Trajectory

Martin Georg Busch1,2, Jürgen Finsterbusch1,2

1Dept. of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; 2Neuroimage Nord, Hamburg-Kiel-Lübeck, Germany

The application of two-dimensional spatially selective RF excitations based on a PROPELLER trajectory for single-voxel proton spectroscopy is presented. Side excitations are minimized by spatially selective refocusing pulses after each PROPELLER blade and adapted RF amplitude weighting. The combination of the half-Fourier method with every blade allows short echo times comparable to those obtained with conventional localization. The localization is tested on phantoms containing Cr and NAA.

                  2604.     MR Spectrocopy of Arbitrarily Shaped Single Voxel Using Segmented, Blipped-Planar 2D-Selective RF Excitations with Weighted Averaging

Jürgen Finsterbusch1,2, Martin G. Busch1,2

1Dept. of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; 2Neuroimage Nord, Hamburg-Kiel-Lübeck, Germany

The target regions of MR spectroscopy usually deviate from the cuboid volume defined with cross-sectional RF excitations yielding partial volume effects (reduced coverage of the target volume and/or signal contributions from surrounding tissue). The capability of 2D-selective RF excitations to excite an arbitrarily shaped regions-of-interest reduces the partial volume effects. Here, weighted averaging combined with a flip adaptation is used to improve the signal-to-noise ratio (SNR) efficiency of an approach using 2DRF based on a blipped-planar trajectory. For the example profile with the shape of a corpus callosum, the SNR could be increased by a factor of about 3.

                  2605.     Comparison of Multi-Element RF Coil Designs for 3D Spatially Selective Excitation

Tim Nielsen1, Peter Börnert1, Ulrich Katscher1, Ingmar Graesslin1

1Philips Research Europe, Hamburg, Germany

Multi-element RF excitation is of high interest to accelerate RF pulses for spatially selective excitation. Coil design, i.e., the encoding capability of a transmit array, has a significant impact on the extent of pulse acceleration. We investigated the performance of different multi-element coil designs with a special focus on 3D excitation. The investigated RF coils consisted of 1 to 4 cylindrical segments with linear antennas oriented parallel to the main field direction and equally distributed around the circumference of each segment. Varying reduction factors and orientations of the trajectory in k-space were investigated.

                  2606.     Robust Large Field-Of-View Water Selective Imaging at 3T with Parallel Transmission

Shaihan J. Malik1, David J. Larkman1, Jo V. Hajnal1

1Imaging Sciences Department, Hammersmith hospital, Imperial College London, London, UK

Spectral fat suppressed or water selective imaging (e.g. using 1331 binomial pulses) is difficult to achieve for large fields-of-view particularly at higher field because of problems in achieving a high-quality shim of the static B0 field. We demonstrate that control of the B1 fields facilitated by parallel transmission technology can be used to improve spectrally selective excitation performance (in both pass and stop bands) over a large field of view, by optimising the relative amplitude and phase of individual sub-pulses.

                  2607.     Slab Selective, Regularized RF Shimming

Ulrich Katscher1, Ingmar Graesslin, Kay Nehrke1, Peter Boernert1

1Philips Research Europe - Hamburg, Hamburg, Germany

RF shimming, i.e., the optimization of a transmit RF coil array's amplitudes and phases, can by applied to compensate wave propagation effects at high main fields. Selected anatomies, e.g., the legs are particularly prone to wave propagation effects, resulting in significant signal inhomogeneities. This study applies RF shimming to 4 volunteer's legs using eight independent transmit channels at 3T. To optimize RF shimming results, a slab selective, separate excitation of the two legs was evaluated in the framework of frequency-encoded transmission. Furthermore, RF shimming was regularized to avoid inhomogeneity compensation on the cost of high SAR.

                  2608.     Considerations for Using Linear Combinations of Array Elements in B1 Mapping

Shaihan J. Malik1, David J. Larkman1, Philip G. Batchelor2, Jo V. Hajnal1

1Robert Steiner MRI Unit, Imaging Sciences Department, Hammersmith hospital, Imperial College London, London, UK; 2Division of Imaging Sciences, King's College London, UK

Accurate B1 mapping of array coils is made difficult by the large dynamic range of flip angles produced by individual coil elements. By mapping the B1 fields from linear combinations of array elements, the dynamic range can be reduced such that existing mapping techniques work more efficiently. The fields produced by individual elements are then inferred by inverting the linear transformation. We investigate the properties of different linear transformations using a single parameter model and various loading conditions in conjunction with the actual flip angle imaging B1 mapping technique.

                  2609.     Estimating K Transmit B1+ Maps from K+1 Scans for Parallel Transmit MRI

Amanda Kay Funai1, Jeffrey A. Fessler1, Douglas C. Noll2

1EECS, University of Michigan, Ann Arbor, MI, USA; 2BME, University of Michigan, Ann Arbor, MI, USA

We propose a method to obtain a map of the complex B1 field strength of K coils using only K+1 measurements. We transmit using coil combinations (leave-one-out) to achieve larger flip angles in the FOV. The proposed method incorporates slice selection effects to create an iterative regularized method with superior results to existing methods.

                  2610.     Phase-Sensitive B1 Mapping with Adiabatic Excitation

Franciszek Hennel1, Sascha Köhler1, Martin Janich2

1Bruker BioSpin MRI, Ettlingen, Germany; 2Intitute of Biomedical Engineering, University of Karlsruhe, Germany

A method for 3D mapping of the radio-frequency field magnitude (B1) is proposed based on the adiabatic half-passage 90-degree excitation. The adiabatic pulse starts the frequency sweep on resonance and generates a pure transverse magnetization with the phase strongly dependent on B1. The method has been applied to map the B1 field of a surface transmit-coil and provided a superior dynamic range compared to the amplitude-based B1-mapping methods.

                  2611.     Optimized Sensitivity for 3D Mapping of the B1 Field Using a Phase-Based Method

Davide Santoro1, Julien Rivoire1, Florian M. Meise1, Maxim Terekhov1, Wolfgang G. Schreiber1

1Section of Medical Physics, Department of Radiology, Mainz University Medical School, Mainz, Germany

A method for 3D B1 Mapping based on the application of a rectangular composite pulse is presented here.

                  2612.     A Novel Method for Simultaneous 3D Mapping of T1, B1 and B0.

Sha Zhao1, Geoffrey J. Parker1

1ISBE, University of Manchester, Manchester, England, UK

We report our newly devised method that maps T1, B1 and B0 in a 3D volume simultaneously. The method is based on the frequency response function of a selective pulse as the preparation applied to a Turbo-FLASH acquisition sequence. The method is easy to conduct, and provides results consistent with alternative independent measurements.

                  2613.     Rapid B1 Mapping in the Presence of B0 Variations

Sohae Chung1, Daniel Kim1, Elodie Breton1, Leon Axel1

1Center for Biomedical Imaging and Radiology, NYU Langone Medical Center, New York, NY, USA

Accurate calibration of B1 field is particularly important at high fields, where large B1 variations can cause flip angle (FA) variations. The most straight-forward "B1 mapping" method is the double angle method. However, it is inefficient due to a need to set TR≥5T1. An alternative approach is to perform a series of RF-prepared TurboFLASH imaging. However, both methods directly measure the FA determined by both B1 and B0, and require a B0 measurement to calculate B1. The purpose of this study was to modify the TurboFLASH imaging to include B0 correction for rapid B1 mapping and to evaluate its accuracy.

                  2614.     In Vivo Mapping of the Peak B1+ Field Strength on a Conventional Scanner

Kyunghyun Sung1, Houchun H. Hu2, Krishna S. Nayak2

1Radiology, Stanford University, Stanford, CA, USA; 2Electrical Engineering, University of Southern California, Los Angeles, CA, USA

Knowledge of the maximum achievable transmit RF (B1+) field strength and its spatial variation enables one to optimize RF pulses and pulse sequences. We present a rapid method for mapping the peak B1+ field strength in vivo using pre-scan variables and previously described methods for relative B1+ mapping. This approach is applied to cardiac imaging on a commercial 3T scanner.

                  2615.     Fast B1+ Mapping with a Function Fit Using a Reduced Number of Support Points

Martin Janich1,2, Olaf Dössel1, Sascha Köhler2, Peter Ullmann2

1Institute of Biomedical Engineering, University of Karlsruhe, Karlsruhe, Germany; 2Bruker BioSpin MRI GmbH, Ettlingen, Germany

Precise B1+ mapping can be performed by fitting of a function to data acquired with different flip angles. Here a reduction of the number of support points used for the fit is proposed, resulting in a significant decrease in scan time. With the fewer support points the same precision was obtained within a limited dynamic range. This dynamic range for correct measurements was determined in simulations. The approach allows fast B1+ mapping and was successfully applied in phantoms and in vivo.

                  2616.     Comparison of EPI and Double Angle B1 Maps at 7T

Douglas Kelley1, Esin Ozturk-Isik2, Janine Lupo2

1Applied Science Laboratory, GE Healthcare, San Francisco, CA, USA; 2Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA

While the double angle method is conceptually the simplest B1 mapping technique, saturation effects force long acquisition times at 7T. Comparison to an unsaturated EPI method in phantoms and volunteers provides a means to assess the saturation effects and establish a minimum acquisition time.

                  2617.     Tailored B1 Mapping for Multi-Element Transmit Applications

Kay Nehrke1, Peter Börnert1

1Philips Research Europe, Hamburg, Germany

Accurate B1-mapping is an essential prerequisite for multi-element transmit applications. However, in vivo B1-mapping is still challenging with respect to scan time and mapping accuracy. Recently, a matrix approach for B1-mapping has been proposed to avoid adverse error propagation in the limit of low flip-angles. In the present work, this concept is extended to tailor the transmit channel encoding matrix used for the mapping scan with respect to the chosen application. This approach is essentially equivalent to the transformation of the problem to an appropriate virtual coil array. The underlying theory will be briefly outlined, and basic feasibility will be evaluated on phantoms and in-vivo.

                  2618.     B1 Mapping and Parallel Excitation Using Vector Decoupling

Adam B. Kerr1, William A. Grissom1, Pascal Stang1, Greig C. Scott1, John M. Pauly1

1Electrical Engineering, Stanford University, Stanford, CA, USA

RF current sensor feedback from a parallel transmit array was used to determine a matrix operator describing the RF voltages to apply to all coils to achieve a desired RF current in a single coil. The vector-decoupled array presented smooth and non-zero B1 maps which facilitated B1 mapping and should reduce spatial resolution requirements. Vector decoupling also enabled iterative predistortion of the parallel RF waveforms which improved RF fidelity and experimental parallel transmit excitation profiles.

                  2619.     TROMBONE: T1-Relaxation-Oblivious Mapping of B1

Roman Fleysher1, Lazar Fleysher1, Matilde Inglese1, Daniel Sodickson1

1Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, USA

We present a method of transmit sensitivity estimation in which distribution of B1 values is extracted from two interleaved 3D spoiled-gradient-recalled-echo (SPGR) images acquired with 3D EPI readouts. The precision is a factor of 6 higher than that of the previously reported Actual Flip angle Imaging method in the same time and spatial resolution.

 
Sequences & Techniques
Exhibit Hall 2-3                    Tuesday 13:30-15:30

                  2620.     Improved High-Resolution Magnetic Resonance Imaging Using a Cylindrical K-Space Sampling Method

Ryan Chamberlain1, Tom M. Wengenack2, Joseph F. Poduslo2, Clifford R. Jack3, Michael Garwood1

1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA; 2Departments of Neurology, Neuroscience, and Biochemistry/Molecular Biology, Mayo Clinic College of Medicine, Rochester, MN, USA; 3Department of Radiology, Mayo Clinic College of Medicine, Rochester, MN, USA

High-resolution 3D imaging of amyloid plaques in transgenic mouse models of Alzheimer's disease has previously been performed using Cartesian k-space sampling. This work investigates cylindrical k-space sampling methods. The k-space data points are still collected on a Cartesian grid, but they are contained within a cylinder instead of a box. The cylindrical methods provide a rotationally invariant point spread function, and they improve the contrast-to-noise ratio of the plaques for a give scan time.

                  2621.     Increased SNR in Echo Planar Imaging (EPI) Using a Circular K-Space Coverage

Anders Nordell1,2, Stefan Skare2,3

1Medical Physics, Karolinska University Hospital, Stockholm, Sweden; 2Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden; 3Radiology, Stanford University, Palo Alto, CA, USA

An Echo Planar Imaging (EPI) pulse sequence with circular k-space coverage is proposed. Earlier published circular EPI (cEPI) had aimed at shortening the total readout length by varying the echo spacing. In our method, covering the same k-space trajectory, the echo spacing is kept constant. Instead the amplitude is changed in order to increase the SNR along the circular echo planar trajectory while keeping a constant k-space velocity along the phase encoding axis, which is important with respect to spatial distortions. We call this method constant velocity circular EPI (cv-cEPI).

                  2622.     3D Cones Trajectory with Anisotropic Field-Of-View

Mahender K. Makhijani1, Krishna S. Nayak1

1Electrical Engg., University of Southern California, Los Angeles, CA, USA

The 3D cones trajectory is the most time efficient scheme for sampling a sphere in k-space, and efficient algorithms are available for the design of readout gradients when the imaging field of view (FOV) and spatial resolution is isotropic. There is an opportunity to further optimize the trajectory design when the anatomic FOV is anisotropic. In this work, we present a method for designing 3D cones trajectory with anisotropic FOV (flat-cylinder) and isotropic spatial resolution. We demonstrate 3D carotid imaging with a 73.2% reduction in scan-time compared to isotropic FOV cones, when the FOV along one axis is one fourth of the FOV along the other two axes.

                  2623.     The Shifted Radial Reordering for Intermediate TE Imaging in 3D Long Echo Train Acquisition

Guobin Li1, Mathias Nittka2, Hans-Peter Hollenbach2, Wilhelm Horger2, Vladimir Jellus2, Stephan Kannengiesser2, Berthold Kiefer2, Timothy Hughes2

1Siemens Mindit Magnetic Resonance Ltd., Shenzhen, Guangdong, China; 2Siemens Medical Solutions, Erlangen, Germany

A shifted radial reordering scheme is proposed for the intermediate TE imaging in 3D long echo train acquisition. This new sampling scheme has been incorporated into SPACE and compared with the linear reordering. The images obtained by the shifted radial reordering scheme present less blurring than those by the conventional linear reordering in 3D long echo train acquisition.

                  2624.     Reducing Distortion in EPI Using Partial Fourier Encoding in the Kx-Direction

Samantha J. Holdsworth1, Roland Bammer1, Stefan Skare1

1Lucas MRS/I Center, Stanford University, Stanford, CA, USA

Geometric distortion in EPI is related to the time between two consecutive echoes in the EPI train. To shorten the EPI readout and TE, the acquisition is often used with partial Fourier encoding in the ky-direction. We propose here to instead perform partial Fourier encoding in the kx-direction. In this way, the echo spacing between two consecutive echoes is reduced – resulting in reduced geometrical distortion while keeping the SNR approximately equivalent. This approach can reduce geometric distortion by ~20% compared with EPI images acquired with partial Fourier encoding in ky.

                  2625.     Cartesian Quasi-Random Sampling for Multiple Contrasts and Dynamic Imaging

Philipp Ehses1, Nicole Seiberlich2, Martin Blaimer3, Felix Breuer3, Wolfgang R. Bauer4, Peter M. Jakob1,3

1Dept. of Experimental Physics 5, Universität Würzburg, Würzburg, Germany; 2Department of Radiology, Case Western Reserve University and University Hospitals of Cleveland, Cleveland, OH, USA; 3Research Center Magnetic Resonance Bavaria (MRB), Würzburg, Germany; 4Dept. of Internal Medicine I, Universität Würzburg, Würzburg, Germany

It has previously been shown that using random numbers to shuffle the phase encoding line order in dynamic MRI allows one to continuously update k-space in a non-orderly fashion. However, even a small set of random numbers may contain elements with very similar values. This observation has lead to the development of quasi-random numbers, which are designed to better obey the intended distribution. We propose a simple method for quasi-random shuffling of the phase encoding line order in Cartesian MRI and demonstrate its application on the example of a single-shot inversion-recovery TrueFISP experiment.

                  2626.     A New Method for Data Acquisition and Image Reconstruction in Parallel Magnetic Resonance Imaging

Refaat ElSayed Gabr1,2, Haitham M. Ahmed2, AbouBakr M. Youssef2, Yasser M. Kadah3

1Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, USA; 2Deptartment of Biomedical Engineering and Systems, Cairo University, Giza, Egypt; 3Medical Imaging Lab, Nile University, Giza, Egypt

We propose a novel data acquisition and image reconstruction method for parallel magnetic resonance imaging. A modification to the parallel imaging system is proposed to allow simultaneous data acquisition using a coil with uniform sensitivity in addition to localized surface coils. The uniform sensitivity coil is included in the image reconstruction technique as an additional coil. The reconstructed image for this coil shows uniform intensity over the field of view that is significantly better than the conventional sum-of-squares reconstruction. The proposed method is tested using real MRI phantom data.

                  2627.     Optimization of K-Space Trajectories by Bayesian Experimental Design

Matthias Seeger1, Hannes Nickisch2, Rolf Pohmann2, Bernhard Schölkopf2

1Saarland University, Saarbrücken, Germany; 2Max Planck Institute for Biological Cybernetics, Tübingen, Germany

We show how improved sequences for magnetic resonance imaging can be found through automated sequential optimization of Bayesian design scores. Combining recent advances in approximate Bayesian inference and natural image statistics with high-performance numerical computation, we propose the first scalable Bayesian experimental design framework for this problem of high relevance to clinical and brain research. Our approach is evaluated on raw data from a 3T MR scanner.

                  2628.     MR Spectroscopic Imaging Using a Concentric Rings Trajectory

Holden H. Wu1, Jin Hyung Lee1, Dwight G. Nishimura1

1Electrical Engineering, Stanford University, Stanford, CA, USA

In this work, we propose the use of a concentric rings readout trajectory for MR spectroscopic imaging (MRSI). The unique circularly symmetric sampling nature of concentric rings enables a time-efficient retracing acquisition to simultaneously encode spatial and spectral information. This acquisition design maximizes the readout duty cycle by continuously retracing each ring with no sampling dead time. MRSI using concentric rings offers a scan time advantage over conventional MRSI, while also demonstrating robustness to eddy currents, timing errors, and gradient delays. Experimental results from an imaging phantom are presented.

                  2629.     ZOOM Imaging of the Human Brain at 7T

Christopher J. Wargo1, Malcolm J. Avison1, E. Brian Welch1,2, John C. Gore1

1Vanderbilt University Institute of Imaging Science, Nashville, TN, USA; 2Philips Medical Systems, USA

The additional signal strength provided by ultra-high field MR systems can be used to increase image resolution at the cost of long scan durations. Often, only a specific anatomical region is of interest, but fold-over prevention necessitates imaging the entire FOV within the desired plane. Spectroscopic techniques such as STEAM, enable spectra to be obtained in targeted brain regions and can be adapted for focused imaging. In this abstract, we describe the use of STEAM to target anatomical regions using so-called “reduced-FOV” or “ZOOM” techniques, with performance demonstrated in excised monkey brain and an awake human subject at 7T.

                  2630.     Multiple Gradient- And Spin-Echo EPI Acquisition Technique with Z-Shimming to Compensate for Susceptibility-Induced Off-Resonance Effects

Heiko Schmiedeskamp1, Matus Straka1, Rexford David Newbould2, Stefan Skare1, Klaas P. Pruessmann3, Roland Bammer1

1Lucas Center, Department of Radiology, Stanford University, Stanford, CA, USA; 2GlaxoSmithKline, London, UK; 3Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

A combined gradient- and spin-echo EPI-based acquisition technique is presented for application in BOLD-fMRI and DSC-PWI. This technique includes additional z-shimming gradients prior to each EPI readout train to compensate for off-resonances in the brain, particularly in regions close to air-tissue interfaces, such as near the auditory canals and nasal cavities. Through root-sum-of-squares combination of multiple EPI trains, signal dropouts in the gradient-echo images could be remarkably reduced to a level similar to that of the spin-echo image acquired at the end of the pulse sequence.

                  2631.     Spin-Echo MRI Using π/2 and π Hyperbolic Secant Pulses

Jang-Yeon Park1, Michael Garwood1

1Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minneapolis, MN, USA

Frequency-modulated (FM) pulses have advantages for spin-echo experiments, such as the ability to produce a broadband and B1-insensitive π rotation. However, such use leads to a non-linear phase of the transverse magnetization. Here, general conditions to compensate the non-linear phase across a slice are proposed for multi-slice spin-echo MRI using π/2 and π hyperbolic secant (HS) pulses. They provide excellent slice-selection and partial B1-insensitivity, as well as a shorter echo-time and lower power deposition than a method using a pair of π HS pulses. One of the conditions also offers a new possibility for chemical-shift selected or susceptibility-weighted imaging.

                  2632.     3D PROPELLER-Based Diffusion Weighted Imaging

Eric Aboussouan1, Jim Pipe1

1Barrow Neurological Institute, Phoenix, AZ, USA

A new sequence dubbed TURBINE (TURBoprop IN Elevation) is proposed which adapts the Turboprop scheme to 3D DWI imaging. The trajectory is based on a Turboprop sequence where the gradient echoes are placed in the slice encoding direction. Benefits over EPI and Turboprop include higher SNR efficiency, lower SAR and MTS, reduced off-resonance artifacts and 3D phase correction.

                  2633.     Single Scan T1 and T2* Mapping Without Flip Angle Correction

Philipp Mörchel1, Gerd Melkus1, Michael Flentje2, Peter Michael Jakob1,3

1Experimental Physics 5, University of Würzburg, Würzburg, Bavaria, Germany; 2Radiation Oncology, University of Würzburg, Würzburg, Bavaria, Germany; 3Research Center for Magnetic Resonance Bavaria (MRB), Würzburg, Bavaria, Germany

A robust method for the simultaneous measurement of T1 and T2* relaxation maps without the need for B1 field corrections based on a modified inversion recovery snapshot FLASH sequence is presented. This method allows for the simultaneous acquisition of T1 and T2* in the time a single T1 measurement using an inversion recovery method would take. Furthermore this sequence is not prone to motion and misregistration artifacts which occur on subsequent measurement of these relaxation parameters. The applicability of this sequence was confirmed using measurements on several phantoms and in vivo.

                  2634.     Fast T2 Mapping Using Partially Spoiled Steady State Free Precession (T2-PSSFP)

Oliver Bieri1, Carl Ganter2, Klaus Scheffler1

1Division of Radiological Physics, University of Basel Hospital, Basel, Switzerland; 2Department of Diagnostic Radiology, Klinikum rechts der Isar, Technical University Munich, Munich, Germany

It was been shown that for small TR and RF spoiling increments (i.e. partial RF spoiling), the width of the transition from SSFP-FID to SPGR is inversely proportional to T2. Using an approximate solution for partially spoiled SSFP sequences allows for fast 3D quantitative T2 mapping.

                  2635.     Robust T1 Mapping in the Presence of Partial Volume Effects

Vasiliki N. Ikonomidou1

1Neuroimmunology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA

Partial volume effects can cause significant errors in T1 estimation. This makes measurement of T1 difficult at the interfaces between brain tissue and cerebrospinal fluid (CSF), such as the cortex. This study presents an optimized technique that combines a saturation and an inversion pulse in order to keep CSF signal suppressed, and allows fitting T1 in a range corresponding to brain tissue while minimizing partial-volume induced error, in a total scantime of 3 minutes.

                  2636.     In-Vivo Volumetric T1 and T2 Quantitation Using Single Acquisition

Ajit Shankaranarayanan1, Eric T. Han1

1Applied Science Lab, GE Healthcare, Menlo Park, CA, USA

The quantification of MR relaxation times has always been of interest since accurate quantitation can lead to improvement in the detection and staging of various diseases. This abstract describes the development of a novel 3D acquisition method for rapid T1 and T2 quantitation for 3D volumes. T1 and T2 values obtained from the new method have been compared to known values in phantom and in-vivo. Such a method has the potential to reduce of total exam time thus increasing the scan efficiency and clinical throughput.

                  2637.     Optimizing Saturation-Recovery Measurements of the Longitudinal Relaxation Rate Under Time Constraints

Jung-Jiin Hsu1, Gary H. Glover1, Greg Zaharchuk1

1Lucas Center for Imaging, Stanford University, Stanford, CA, USA

The oxygen concentration in cerebrospinal fluid (CSF) can be determined by CSF's longitudinal relaxation time T1. Because CSF has long T1, the T1 measurement can be very time-consuming. For CSF MR oximetry to be clinically feasible, the total scan time must be shortened. In this work, Monte Carlo computer simulation was carried out to determine the optimal imaging parameters under strict constraints of constant total scan time. With the optimization, three-dimensional, high resolution, whole brain saturation-recovery scans can be completed in 10 minutes and can generate CSF relaxation measurements in agreement with the best literature results.

                  2638.     Automatic High-Order Shimming by Sampling Columns in the Cartesian Coordinates

Yan Zhang1, Shizhe Li1, Jun Shen1

1National Institute of Mental Health, Bethesda, MD, USA

A new automatic high-order shimming method is presented which performs the field mapping by sampling a group of columns in the Cartesian coordinate system. It was found that a minimum of a pair of four columns in two separate slices could unambiguously determine an optimal correction field that comprises the spherical harmonic terms up to the third-order. The technique of multiple stimulated echoes was incorporated into the method, allowing the use of eight or more shots to accomplish field mapping. The shim currents were first determined in the logic frame by assuming the slices were in axial planes, and then uniquely converted into the physical frame where the slices could be at any oblique angle, by using a spherical harmonics rotation transformation.

                  2639.     Dual Flyback Echo-Planar Imaging for Separation of Water and Fat

Kyunghyun Sung1, Brian A. Hargreaves1

1Radiology, Stanford University, Stanford, CA, USA

Dixon techniques are considered as one of the practical methods to suppress fat at a cost of additional scan time. Dual-echo Dixon techniques have recently shown great promise for very rapid imaging and robust separation with careful phase correction algorithms. In this work, we extend this dual-echo method using a dual flyback echo-planar imaging to further speed the acquisition of data. The new phase estimation method is proposed to include correction for a relative phase-direction shift of fat and water. We demonstrate in vivo water and fat separation for abdominal imaging.

                  2640.     Faster Fat-Water Imaging with a Novel Multislice Time-Shifted GRASE-Dixon Sequence.

Kuan J. Lee1, Jochen Leupold1

1Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, 79106, Germany

A new multislice GRASE-Dixon imaging sequence is introduced which can double the rate at which slices are acquired for Dixon fat-water imaging. Current implementations have a minimum interval between consecutive refocusing pulses which determines the minimum acquisition time. Our sequence uses some of the time on one side of the spin-echo from one slice to fit in the refocusing pulse from another slice; thus, an extra slice is acquired in the same time. The excitation and refocusing pulses from one slice are time-shifted relative to those from the other slice, thereby maintaining CPMG conditions. In-vivo results at 1.5T are shown.

                  2641.     Effect of K-Space Sampling Pattern on SNR in Parallel MRI Accelerated IDEAL Sequences.

Shawn Joseph Kisch1, Philip M. Robson2, Catherine DG. Hines3, Bryan T. Addeman1, Huanzhou Yu4, Ann Shimakawa4, Ananth Madhuranthakam4, Ajit Shankaranarayanan4, Jean Brittain4, Scott Reeder3, Charles McKenzie1,5

1Department of Medical Biophysics, University of Western Ontario, London, ON, Canada; 2Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA; 3Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA; 4Applied Sciences Laboratory, GE Healthcare; 5Department of Biomedical Engineering, University of Western Ontario, London, ON, Canada

We investigate the variation in signal-to-noise-ratio (SNR) in parallel MRI accelerated IDEAL images due to the k-space sampling pattern. The pseudo replica SNR measurement used allows for an accurate measurement of SNR in both liver water and liver fat images produced by the IDEAL sequence. A comparison between different sampling patterns in each IDEAL echo with an overall acceleration factor of two in a PMRI sequence is made. The results show that the SNR is independent of the choice of calibration echo, but is maximized when a uniform k-space sampling pattern is used.

                  2642.     Fat Suppression with Slice-Selection Gradient Reversal (SSGR) Revisited;

Taro Takahara1, Jaco Zwanenburg2, Fredy Fisser1, Tetsuo Ogino3, Dennis Klomp2, Hans Hoogduin2, Jeroen Hendrikse1, Thomas Kwee1, Willem Mali1, Peter Luijten1

1Radiology, University Medical Center Utrecht, Utrecht, Netherlands; 2Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands; 3Philips Electronics Japan, Japan

The Slice-Selective Gradient Reversal (SSGR) technique is very effective for robust fat suppression, especially at high field strength (> 1.5T), and can be combined with Spectral Prostration with Inversion Recovery (SPIR) for even better results. As the technique does not introduce any additional scan time or Specific Absorption Rate (SAR), it should be used in spin-echo type sequences at high-filed strength. Particularly for the application of whole body diffusion techniques (DWIBS) at high field, the improved fat suppression may substantially improve image quality.

                  2643.     Fast Fat Suppression Technique for Adaptive 3D Radial MRI Based on Multidimensional Golden Means

Peter Siegler1, Rachel Wai-chung Chan2, Elizabeth Ramsay1, Donald Bruce Plewes1

1Imaging Research, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; 2Medical Biophysics, University of Toronto, Toronto, Ontario, Canada

Adaptive sampling of k-space allows the reconstruction of images with various spatial and temporal resolutions from the same data set and is therefore suitable for dynamic MRI. 3D projection reconstruction based on multidimensional golden means (golden 3D-PR) achieve this flexibility for any time interval. In this work, partial fat saturation in combination with the k-space-weighted image contrast (KWIC) technique is used for fast fat suppression of golden 3D-PR. KWIC processing greatly increases the efficiency of the applied partial fat saturation. The new technique allows fat suppression of adaptive golden 3D-PR data sets with high temporal resolution.

                  2644.     Water-Fat Separation Based on T1 Relaxation Times Using Inversion Recovery BSSFP MR Imaging

James W. Goldfarb1

1Saint Francis Hospital, Roslyn, NY, USA

Fat water separation based on T1 relaxation times can be robustly performed using an IR-bSSFP acquisition. The technique provides suppression on the order of the background noise and is insensitive to magnetic field inhomogeneities.

                  2645.     Fast-Spin-Echo Imaging and Fat/Water Separation Using a Concentric Rings Trajectory

Holden H. Wu1, Jin Hyung Lee1, Dwight G. Nishimura1

1Electrical Engineering, Stanford University, Stanford, CA, USA

The concentric rings 2D trajectory is inherently centric-ordered, provides smooth weighting in k-space, and enables shorter scan times. These properties make it well suited as a readout trajectory for fast-spin-echo imaging where T2 decay modulates the acquisition. The rings offer a reduction in the number of refocusing pulses, which can be used to reduce the scan time, improve SNR or resolution, or decrease the RF power per TR. In addition, the unique circularly-symmetric sampling nature of the rings enables a time-efficient retracing acquisition for fat/water separation. This allows the rings to be robust to bright fat signal arising from multiple refocusing pulses.

                  2646.     Compressive Chemical-Shift-Based Rapid Fat/Water Imaging

Michael Lustig1, John Mark Pauly1

1Electrical Engineering, Stanford University, Stanford, CA, USA

A chemical-shift fat/water imaging technique based on compressed sensing is presented. Full chemical-shift imaging spectra are obtained from randomly undersampled phase-encodes acquired at randomized echo-times. The reconstruction enforces both spatial and spectral sparsity of the images.

                  2647.     3D Magnetization-Prepared Imaging and Fat/Water Separation Using a Stack-Of-Rings Trajectory

Holden H. Wu1, Jin Hyung Lee1, Dwight G. Nishimura1

1Electrical Engineering, Stanford University, Stanford, CA, USA

In this work, we extend the 2D concentric rings k-space trajectory to a 3D stack-of-rings acquisition for volumetric spatial coverage. The 3D stack-of-rings trajectory inherits the desirable properties of the 2D concentric rings and offers even more flexibility in designing efficient magnetization-prepared imaging sequences. In addition, the unique circularly-symmetric sampling nature of the rings enables a time-efficient retracing acquisition for fat/water separation to ensure the robustness of this 3D non-Cartesian trajectory to off-resonance effects. Experimental results are shown for the case of magnetization-prepared imaging of the human brain.

                  2648.     Ultra-Short TR Contrast-Enhanced MR Angiography with Spiral Centric Phase Reordering

Yutaka Natsuaki1, Randall Kroeker2, Peter Schmitt3, Gerhard Laub1

1Siemens Medical Solutions USA Inc, Los Angeles, CA, USA; 2Siemens Medical Solutions, Winnipeg, MB, Canada; 3Siemens Healthcare AG, Erlangen, Germany

For the contrast enhanced MR angiography (CE MRA) with a 3D Spoiled GRE sequence, the speed is a primary design requirement. One way to improve speed in CEMRA is to maximize the sequence efficiency (i.e. the ratio between DAQ event and TR) by skipping the phase encoding (PE) rewinders. This, however, will have a consequence of enhanced background phase coherence artifacts. The current study proposes a novel Spiral Centric phase reordering algorithm that significantly reduces the phase coherence artifacts and allows ultra-short TR CE MRA while skipping PE rewinders.

                  2649.     Max CAPR: High Temporal and Spatial Resolution 3D CE-MRA with Scan Times Under Five Seconds

Clifton R. Haider1, John Huston III1, Norbert G. Campeau1, James F. Glockner1, Anthony W. Stanson1, Stephen J. Riederer1

1Radiology, Mayo Clinic, Rochester, MN, USA

It is assumed in view-shared time-resolved 3D CE-MRA that spatial frequencies not updated every frame have limited variation over time. This is not the case. As the time spent in acquiring data used to reconstruct a frame increases, so does the susceptibility to time-related artifacts. Undersampling the CAPR sequence can eliminate view sharing, causing the temporal footprint to match the frame time. Due to its specific k-space sampling pattern, this can be done with CAPR without degrading the spatial resolution. 1 mm isotropic resolution results are demonstrated in MRA of the calves with image acquisition times less than 5 sec.

                  2650.     ToF-SWI: A Dual-Echo Sequence for Simultaneous Time-Of-Flight Angiography and Susceptibility Weighted Imaging

Andreas Deistung1, Enrico Dittrich1,2, Jan Sedlacik3, Alexander Rauscher4, Jürgen R. Reichenbach1

1Medical Physics Group, Institute for Diagnostic and Interventional Radiology, University Clinics, Friedrich-Schiller-University, Jena, Germany; 2Department of Medical Engineering and Biotechnology, University of Applied Sciences, Jena, Germany; 3Radiological Sciences, Translational Imaging, St. Jude Children's Research Hospital, Memphis, USA; 4MRI Research Centre, University of British Columbia, Vancouver, Canada

We present an MR-sequence for non-invasive simultaneous arterial and venous imaging based on a 3D dual-echo gradient echo sequence (ToF-SWI) that combines time-of-flight (ToF) angiography and susceptibility weighted imaging (SWI). The influence of flip angle (FA), parallel imaging acceleration factor, and the issue whether full flow compensation of the second echo is required was investigated. We found good vessel representation for a ramped flip angle (20°) and an acceleration factor up to R=3. Full (3D) flow compensation of the second echo was required to minimize signal voids and mis-registration of arteries due to oblique blood flow.

                  2651.     Simultaneous Acquisition of High-Resolution T2-Weighted and Cerebro-Spinal-Fluid-Suppressed Images Using Phase-Sensitive Dual-Acquisition Single-Slab Three-Dimensional Turbo Spin Echo Sequence

Jaeseok Park1, Eung Yeop Kim1,2

1Department of Radiology and Research Institute of Radiological Science, Yonsei University College of Medicine, Seoul, Korea; 2Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Korea

Small brain lesions such as multiple sclerosis (MS) are the most frequent inflammatory demyelinting disease of the central nervous system. T2-weighted imaging is a gold standard for diagnosing infratentorial brain lesions, while fluid-attenuated-inversion-recovery (FLAIR) imaging is known to be highly sensitive to lesions close to cerebro-spinal-fluid (CSF) but less sensitive in posterior fossa. Additionally, high-resolution three-dimensional (3D) imaging is preferred due to the small size of lesions. Given the facts above, the purpose of this work is to develop a novel phase-sensitive dual-acquisition single-slab 3D turbo/fast spin echo (SE) pulse sequence for acquiring both T2-weighted and CSF-suppressed images simultaneously in a single measurement.

                  2652.     Improving Contrast in 3D Structural Brain Imaging at 3T by Incorporating Magnetisation Transfer Pulses Into MDEFT (MT-MDEFT)

David L. Thomas1, Nikolaus Weiskopf2, Roger J. Ordidge1

1Department of Medical Physics and Bioengineering, University College London, London, UK; 2Wellcome Trust Centre for Neuroimaging, University College London, London, UK

3D MDEFT is an established imaging technique for whole brain T1-weighted imaging, particularly at high field strength. In this work, we describe a modification to the MDEFT sequence which increases the CNR of GM, WM and CSF in the brain. We achieve this by adding magnetisation transfer (MT) pulses to the first part of the MDEFT preparation period. The contrast introduced by these MT pulses combines constructively with the inherent T1 contrast to produce images with higher CNR than standard MDEFT. Mean CNR increases are WM/GM = 5% and GM/CSF = 24%.

                  2653.     Dual Contrast 3D-TSE, T2w and FLAIR Imaging at 7.0 Tesla

Fredy Visser1,2, Jaco Zwanenburg3, Hans Hoogduin3, Peter Luijten3

1University Medical Centre Utrecht, Utrecht, Netherlands; 2Philips Healthcare, Best, Netherlands; 3UMC

Non selective 3D-TSE acquisition with advanced refocusing pulse angle sweep has become an important technique in neuro-radiology. It can resolve the problem of partial volume effects and inherent CSF-inflow artifacts in FLAIR. However, scan times are inherently long especially when both T2w and FLAIR are required for the clinical application. This study shows a 3D TSE sequence with high SENSE factor that produces a T2w as well as a FLAIR image in a single experiment at 7T.

                  2654.     3D Double Echo TrueFISP and FLASH Ultra-Short Echo Time Musculoskeletal Imaging

Sonia Nielles-Vallespin1, Peter Speier1, Peter Weale2, Saurabh Shah2, Edgar Mueller1

1Cardiovascular MR, Siemens AG Healthcare Sector, Erlangen, Germany; 2Cardiovascular MR, Siemens AG Healthcare Sector, Chicago, USA

Double Echo TrueFISP and FLASH Ultra-short Echo Time (UTE) images of the head are presented and compared in terms of signal-to-noise ratio (SNR) and depiction of the short T2 components. The results demonstrate that a 3D TrueFISP UTE acquisition would provide significantly increased contrast, SNR and less sensitivity to eddy currents than a FLASH UTE acquisition. TrueFISP difference images showed up to 1.6 time higher SNR than FLASH difference images and better suppression of long T2 components. The delineation of bone appears much more precise in the TrueFISP subtraction image for identical acquisition time.

                  2655.     Balanced Steady-State Feedback Radiation Damping: Balanced SSFR

Florian Wiesinger1, Eric Fiveland2, Christopher Judson Hardy2

1Imaging Technologies, GE Global Research, Munich, Germany; 2MRI Laboratory, GE Global Research, Niskayuna, NY, USA

Radiation damping (RD) is a second-order effect where the signal-induced current in the receiver coil is strong enough to act back on the signal-generating spins. Accordingly, it can be understood as a self-regulating flip-back pulse. Active radiation damping feedback loops have been introduced into the transmit-receive RF signal path as a means to either cancel, or amplify the natural RD effect. Recently, Huang et al used RD feedback to actively control the recovery of longitudinal magnetization immediately following a non-selective saturation pulse. Here we investigate RD feedback as a means to achieve increased SNR efficiency for short-TR, gradient-echo sequences.

                  2656.     Free Breathing Cardiac Cine Imaging with  Self-Gated Dual-Echo SSFP

Daniel A. Herzka1, Elliot R. McVeigh1, S. Laurence Lee1, Peter Kellman2, Robert J. Lederman3, J. Andrew Derbyshire3

1Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA; 2Laboratory of Cardiac Energetics, NHLBI, NIH, DHHS, Bethesda, MD, USA; 3Translational Medicine Branch, NHLBI, NIH, DHHS, Bethesda, MD, USA

Self-navigation has recently become an alternative to breath-holding or respiratory navigators for cardiac imaging. Here, we present a balanced SSFP-based fast imaging sequence that acquires imaging data along with a constant navigator projection every TR. The navigator projection angle is independent of readout orientation. The sequence was used to acquire free-breathing cine loops in both short and long axis views in normal subjects. TR ranged from 5.3-5.9ms using hardware optimized gradient waveforms and partial Fourier imaging. Acquisition efficiency per TR was maintained relative to single-echo SSFP. The sequence has possible clinical application whenever breath-holds are not possible or unfeasibly long.

                  2657.     First Order Catalyzing of the Non-CPMG Sequence.

Patrick H. Le Roux1,2

1Applied Science Lab, GE Healthcare, Palaiseau, France; 2SHFJ, CEA, Orsay, France

The non-CPMG sequence is a spin echo sequence that permits to obtain a full magnitude signal even in the presence of initial phase variation. It employs a quadratic phase modulation of the refocusing pulses in front of which one must include a train of stabilizing pulses to put the magnetization in an appropriate state. This ‘catalysing ‘ period has been to date determined by optimization. We show that for nutation close to 180° (in a 160°-200° range) the state towards which one must drive the magnetization, but also the series of pulses able to do so, can be derived analytically.

                  2658.     Variable Flip Angle Steady State Free Precession Imaging for Reduction of SAR

Suguru Yokosawa1, Yo Taniguchi1, Yoshitaka Bito1

1Central Research Laboratory, Hitachi, Ltd., Kokubunji, Tokyo, Japan

We have proposed two VFA schemes to reduce the SAR while maintaining both the SNR and image contrast for both gated and non-gated SSFP imaging. The main idea of the technique is to use a high flip angle for echoes around the center of a k-space and at times prior to when the echo for the center was obtained. We examined the SNR and contrast of the healthy volunteer images by comparing a VFA scheme to a constant flip angle scheme. The results show that the proposed schemes reduced the SAR by 30% while maintaining the SNR and image contrast.

                  2659.     CAIPIRINHA Accelerated Simultaneous Multi-Slice TrueFISP Real-Time Imaging

Daniel Stäb1, Marcel Gutberlet1, Felix Breuer2, Martin Blaimer2, Dietbert Hahn1, Herbert Köstler1

1Institut für Roentgendiagnostik, Universitätsklinikum Würzburg, Würzburg, Bavaria, Germany; 2Research Center Magnetic Resonance Bavaria, Würzburg, Bavaria, Germany

Aim of this study was to combine CAIPIRINHA accelerated multi-slice imaging, with TrueFISP. However, due to the constraint to maintain the steady state, the implementation of CAIPIRINHA which enables the simultaneous acquisition of several slices, is only achievable by segmenting the acquisition rendering real-time applications impossible. With the presented new approach the steady state could be maintained without segmenting the acquisition by applying individual phase cycles to each slice. High quality images were reconstructed performing phantom experiments and real-time imaging of the human heart in two slices simultaneously.

                  2660.     Balanced SSFP Imaging with Variable Tip Angles and Repetition Times

Tolga Çukur1, Dwight G. Nishimura1

1Electrical Engineering, Stanford University, Stanford, CA, USA

Regular balanced (b)SSFP sequences produce a spectral response composed of periodic pass-bands. Previous work has focused on periodically alternating either the repetition times (TRs) or the tip angles to generate a stop-band around the fat resonance or to widen the central pass-band. In this work, we develop a framework to combine variable-tips and variable-TRs, and analyze the effects of such modifications on the resulting response by treating them as spectrally selective RF pulses applied within a single-TR of a regular bSSFP sequence. With this framework, we propose designs with significantly improved responses while allowing flexible parameter selection.

                  2661.     Variable Flip Angle Schedules for Detecting Prepared Longitudinal Magnetization in Snapshot Balanced SSFP

Travis B. Smith1, Zungho Zun1, Eric Wong2, Krishna S. Nayak1

1Department of Electrical Engineering, University of Southern California, Los Angeles, CA, USA; 2Departments of Radiology and Psychiatry, University of California, San Diego, La Jolla, CA, USA

Tissue characterization by MRI often involves the subtraction of images obtained with and without a preparation of the longitudinal magnetization (e.g. T2 preparation, arterial spin labeling, and diffusion preparation). Studies that use snapshot balanced steady state free precession typically utilize a brief catalyzation and constant flip angle during acquisition to reach the steady state more quickly. We introduce variable flip angle schedules optimized for the detection of differences in the longitudinal magnetization of the tissue of interest based on its relaxation times. In myocardium, this approach is shown to achieve 18% higher SNR in difference images compared to the conventional approach.

                  2662.     Implementation of a 3D Isotropic Ultra-Shot TE (UTE) Sequence

Tiejun Zhao1, Yongxian Qian2, Yik-Kiong Hue2, Tamer S. Ibrahim2, Fernando Boada2

1Siemens Medical Solutions, USA, Pittsburgh, PA, USA; 2University of Pittsburgh, Pittsburgh, PA, USA

A new UTE sequence is demonstrated by a combination of short RF pulse for excitation and 3D data acquisition scheme that rotates the 2D spiral trajectory. The image quality from this method was evaluated and its capabilities for imaging the fast relaxation T2 relaxation materials were demonstrated.

                  2663.     A Modified EPI Sequence for High-Resolution Imaging at Ultra-Short Echo Times

Stefan Hetzer1, Toralf Mildner1, Harald E. Möller1

1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany

An EPI modification which achieves high SNR is proposed. k-space is sampled in two tiles along phase-encoding direction by center-out trajectories with a minimal delay achieving a similar efficiency as single-shot EPI. Inter-segment phase and intensity imperfections can be easily corrected with the information from both central lines, which are subsequently averaged for SNR optimization. Phase errors from field inhomogeneities are corrected in the Fourier domain, recovering the superior point-spread function. The ultra-short echo time (&#8776;2 ms) is nearly independent of the resolution permitting a variety of applications that require high spatial and temporal resolution.

                  2664.     Minimizing Spiral Image Blurring on Whole-Body 7T Scanner with Multi-Shots and UTE Acquisitions

Yongxian Qian1, Tiejun Zhao2, Yik-Kiong Hue1, Tamer S. Ibrahim1, Fernando E. Boada1

1Department of Radiology, University of Pittsburgh, Pittsburgh, PA, USA; 2R&D, Siemens Medical Solutions USA, Pittsburgh, PA, USA

This study presents a new approach which minimizes spiral image blurring on a whole-body 7T scanner. A combined use of multi-shot spirals and ultra-short echo time (UTE) acquisitions was implemented in this approach and high-resolution (0.22mm) brain images of healthy volunteers were obtained. These T1-weighted FID-based images clearly show the effectiveness of the proposed approach.

                  2665.     3-Directional Fast Acceleration Encoding

Felix Staehle1, Simon Bauer1, Bernd André Jung1, Jürgen Hennig1, Michael Markl1

1Department of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany

This abstract presents a 3-directional acceleration encoding strategy with optimized gradient waveforms to reduce the echo time TE considerably. The encoding strategy was successfully validated using a rotating phantom. Its feasibility for in-vivo measurements was demonstrated in a volunteer measurement of a midventricular short-axis slice of the myocardium. The directly measured acceleration data demonstrated good agreement with acceleration data obtained by calculating the derivative from velocity data measured on the same volunteer.

                  2666.     Methods for Measuring Intercompartmental Exchange: Aqueous Urea as a Model System

Richard D. Dortch1,2, Adam R. Horch1,2, Mark D. Does1,2

1Biomedical Engineering, Vanderbilt University, Nashville, TN, USA; 2Institute of Imaging Science, Vanderbilt University, Nashville , TN, USA

Inverting T2 decay data into a relaxation distribution —via inverse Laplace transform methods — allows one decompose bulk NMR signal into components that represent underlying microanatomical tissue compartments. Intercompartmental exchange is often ignored in this analysis, as it is not possible to fully invert the system from T2 data alone when exchange is included; however, exchange can have a significant effect on the extracted pool sizes and T2s. In this study, a novel approach for measuring intercompartmental exchange, which allows one to significantly reduce scan time relative to existing approaches, is presented and validated in an aqueous urea model.

                  2667.     Small FOV Imaging Using Wavelet Encoding with 2 Dimensional RF Pulses and Gradient Echo

Hacene Serrai1, Richard Young1

1National Research Council, Institute for Biodiagnostics , Winnipeg, Manitoba, Canada

This paper address the problem of folding in the small FOV MR imaging by replacing the usual phase encoding (Fourier encoding) by wavelet encoding. Two dimensional radio-frequency pulses are inserted into a Gradient-Echo sequence where phase encoding gradient is removed. Slice selection and wavelet encoding steps are simultaneously achieved with the 2D RF pulse, which plays the role of the wavelet functions. They are translated and dilated by changing the gradient strength and shifting the frequency of the RF pulses. The results show that wavelet encoding provides images without aliasing while preserving the object information.

                  2668.     Maximizing the Hyperpolarized Signal for a T1 Compensated Variable Angle Acquisition

Shawn Wagner1,2, Pratip Bhattacharya1, Brain D. Ross1,2

1Enhanced MR Laboratory, Huntington Medical Research Institutes, Pasadena, CA, USA; 2Rudi Schulte Research Institute, Santa Barbara, CA, USA

We investigated how to maximize the signal obtained with a variable angle pulse scheme used for imaging hyperpolarized compounds. By using different hypothetical T1 values we compare the total signal acquisition over a 60 second time window for 12 five second acquisitions. The calculations demonstrate that there is a signal advantage to repeating the same variable angle sequence over each image acquisition when compared to a continuous variable pulse angle ending in a 90 degree pulse.

                  2669.     Toeplitz Random Encoding for Reduced Acquisition Using Compressed Sensing

Haifeng Wang1, Dong Liang1, Kevin F. King2, Leslie Ying1

1Department of Electrical Engineering and Computer Science, University of Wisconsin - Milwaukee, Milawukee, WI, USA; 2Applied Science Laboratory, GE Healthcare, Waukesha, WI, USA

Considerable attention has been paid to compressed sensing (CS) in the MRI community recently. CS theory allows exact recovery of a sparse signal from a highly incomplete set of samples in conventional sense, and thus has the potential for significant reduction in MRI scan time. While most existing work has focused on Fourier encoding, some has show promises in non-Fourier encoding. In this abstract, we design a pulse sequence to implement the Toeplitz random encoding method proposed earlier. The experiment results show that Toeplitz random encoding can be realized in practice as an alternative method for CS MRI.

                  2670.     Single-Scan Spatially Encoded MRI - Principles & Applications

Noam Ben-Eliezer1, Yoav Shrot1, Lucio Frydman1

1Chemical Physics, Weizmann Institute of Science, Rehovot, Israel

In recent studies we have introduced an alternative scheme for ultrafast imaging based on imparting a spatial rather than a conventional temporal encoding of the spins interactions. We continue to explore this approach using an integrated spatio-temporal encoded technique producing 2D single-shot images under non-ideal conditions. This ‘hybrid’ imaging scheme is shown to be superior to traditional protocols such as Spin-Echo EPI, in non-homogeneous magnetic field environments. Further enhancements of the basic technique are presented, capable of producing T2* self-refocused images as well as significant decreases in the image acquisition time by employing a novel encoding and post-processing scheme.

                  2671.     General Time-Encoding Description and Improved RASER Imaging

Ryan Chamberlain1, Michael Garwood1

1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA

RASER provides purely T2-weighted single-shot images that show promise for fMRI studies in areas of the brain that are difficult to image with EPI. The basis of RASER is time-encoding. In this work, we provide a general description of time-encoding for any excitation pulse with frequency and gradient modulation, along with an analysis of the SNR possible with time-encoding, and a comparison of the time-encoded signal produced by chirp, HS20, and HS40 pulses.

                  2672.     Implementation of SWIFT on a Siemens Clinical Scanner

Julien Valette1, Steen Moeller2, Djaudat Idiyatullin2, Curt Corum2, Denis Le Bihan1, Michael Garwood2, Franck Lethimonnier1

1CEA - NeuroSpin, Gif-sur-Yvette, France; 2CMRR - University of Minnesota, Minneapolis, MN, USA

SWIFT (sweep imaging with Fourier transformation) is a recently introduced MRI technique, which offers novel and beneficial properties compared to conventional MRI sequences. In particular, SWIFT is extremely quiet and allows imaging ultra short T2 nuclei, and may therefore prove beneficial in a clinical environment. However, due to its non-conventional nature, the implementation of SWIFT on a clinical scanner is challenging. In this context, the goal of this work was to assess the feasibility of SWIFT implementation on Siemens clinical scanners.

                  2673.     Phase Encoding Without Gradients at High Field: TRASE RF MRI at 3T

Scott B. King1, Peter Latta1, Vyacheslav Volotovskyy1, Jonathan C. Sharp2, Boguslaw Tomanek2

1National Research Council of Canada, Institute for Biodiagnostics, Winnipeg, Manitoba, Canada; 2National Research Council of Canada, Institute for Biodiagnostics (West), Calgary, Alberta, Canada

Recently, a new RF B1-field method of spatial encoding was introduced whereby k-space is traversed in the phase encoding direction without using B0 field gradients, but by applying different B1-phase gradient fields produced by a Tx-array, TRansmit Array Spatial Encoding (TRASE). We demonstrate 1D gradient-free TRASE MRI of large phantom and fixed brain within inhomogeneous B1 fields at 3T using both a switched 1- and 8-channel transmitter, and a 2-channel spiral birdcage array. Once perfected, this new silent k-space traversal method will allow the exploration of new data acquisition schemes that may reduce gradient related artifacts/deficiencies and improve imaging speed.

                  2674.     Can RF Encoding Improve Parallel Imaging?

Rita Gouveia Nunes1, Joseph V. Hajnal1, David J. Larkman1

1Robert Steiner MRI Unit,  Imaging Sciences Department, MRC Clinical Sciences Centre, Hammersmith Hospital, Imperial College London, London, UK

Scanning times can be reduced by combining gradient and coil encoding - Partially Parallel Imaging (PPI). Adding RF encoding to PPI can improve reconstruction quality for particular gradient encoding schemes. We investigate if this result is general in the absence of prior object knowledge. Simulated PPI reconstruction matrices were built for several schemes and modified using RF modulation. The set of RF modulations leading to lowest condition numbers were sought. No improvements were observed for regular sampling. Other schemes benefited from RF encoding, with condition numbers reducing to the level of non-RF modulated regular matrices.

                  2675.     Analysis of TRASE Echo Train Pulse Sequences for RF Imaging

Jonathan Sharp1, Scott B. King2, Donghui Yin2, Peter Latta2, Boguslaw Tomanek3

1Institute for Biodiagnostics (West), National Research Council of Canada, Calgary , AB, Canada; 2Institute for Biodiagnostics, National Research Council of Canada, Winnipeg, MB, Canada; 3Institute for Biodiagnostics (West), National Research Council of Canada, Calgary, AB, Canada

The TRASE method (Transmit Spatial Encoding) exploits the spatial information present in the RF phase gradient to achieve 1D, 2D or 3D imaging and slice selection in echo trains in which each echo is encoded to a different k-space location. High spatial resolution relies on the maintenance of echo amplitude and phase evolution down the echo train. Since phase gradient fields cause pulse phase to become a function of position, different points in the sample see different pulse sequences. Here we study the design of these sets of echo trains for 1D imaging, examining sensitivity to off-resonance and B1 inhomogeneity.

                  2676.     Reference-Free Parallel Imaging with Phase Scrambling (PIPS)

Maxim Zaitsev1, Jürgen Hennig1

1Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany

A combination of phase-scrambled MRI using a quadratic phase modulation with traditional parallel imaging methods is presented demonstrating a possibility of a full FOV full resolution image reconstruction based on the undesampled k-space data alone, without requiring neither prior knowledge of coil sensitivity maps nor additional auto-calibrating k-space lines.

                  2677.     Wideband Parallel Imaging

Fu-Hsing Wu1, Edzer Wu2, Li-Wei Kuo2, Jyh-Horng Chen2, Tzi-Dar Chiueh3

1Interdisciplinary MRI/MRS Lab, , Department of Electrical Engineering,, Taipei, Taiwan; 2Interdisciplinary MRI/MRS Lab,, Department of Electrical Engineering,, Taipei, Taiwan; 3MicroSystem Research Lab,, Department of Electrical Engineering,, Taipei, Taiwan

Human lower limb images were successfully acquired with an acceleration rate of up to 8x by using wideband parallel imaging. The non-uniform multislice profile problem of this technique was successfully compensated to enhance the image quality of the outer slices. Also the signal-to-noise ratio (SNR) of this ultra fast imaging technique, wideband parallel imaging, was verified to be similar with that of gradient echo with GRAPPA.

                  2678.     Wideband MRI: A New Dimension of MR Image Acceleration

Edzer Lienson Wu1,2, Jyh-Horng Chen2,3, Tzi-Dar Chiueh3

1Biomedical Engineering, National Taiwan University, Taipei, Taiwan; 2Interdiciplinary MRI/MRS Lab, National Taiwan University, Taipei, Taiwan; 3Electrical Engineering, National Taiwan University, Taipei, Taiwan

We propose a new paradigm of MRI acceleration using the frequency multiplexing technique in modern communication technology; we name it “Wideband MRI”. A major component of wideband MRI is frequency multiplexing of MR signals. Using simultaneous multi-slice RF excitation pulses centered at different frequencies followed by simultaneous multi-slice acquisition during readout, the total scan time of a subject can be significantly reduced using existing hardware. Mathematical model and experimental results explain Wideband MRI image quality and serves as a criterion to evaluate the tradeoff between imaging speed and image quality in future applications.

 
Sequences: Applications
Exhibit Hall 2-3                    Wednesday 13:30-15:30

                  2679.     3D Isotropic Brain Imaging Using Wideband MRI

Edzer Lienson Wu1,2, Tzi-Dar Chiueh3, Jyh-Horng Chen2,3

1Biomedical Engineering, National Taiwan University, Taipei, Taiwan; 2Interdiciplinary MRI/MRS Lab, National Taiwan University, Taipei, Taiwan; 3Electrical Engineering, National Taiwan University, Taipei, Taiwan

Using Wideband simultaneous multi-slab 3D MRI we have acquired a whole brain image with high isotropic spatial resolution of 0.78x0.78x0.78mm3 in only 8m11s. Acquisition time is reduced by 75% compared to conventional 3D MRI with same imaging parameters.

                  2680.     Reduction of Diffusion Tensor Imaging Acquisition Time with Wideband MR Imaging

Edzer Lienson Wu1,2, Kuan-Hung Cho2,3, Tzi-Dar Chiueh3, Jyh-Horng Chen2,3

1Biomedical Engineering, National Taiwan University, Taipei, Taiwan; 2Interdiciplinary MRI/MRS Lab, National Taiwan University, Taipei, Taiwan; 3Electrical Engineering, National Taiwan University, Taipei, Taiwan

A Wideband diffusion tensor imaging is successfully performed to acquire two images in one single excitation. 2-slices are excited/acquired simultaneously using 2D Wideband modified pulse-gradient spin-echo sequence. The calculated diffusion tensors of the grapefruit are clearly displayed on the eigenvector map, and proven to be correct. The result of this study directly indicates a reduction of more than half the time for diffusion tensor imaging of large coverage such as whole brain DTI.

                  2681.     Noise Analysis for 3-Pt Chemical Shift Based Water-Fat Separation with Accurate Spectral Modeling

Venkata Veerendranadh Chebrolu1, Huanzhou Yu2, Angel R. Pineda3, Charles McKenzie4, Jean H. Brittain5, Scott B. Reeder6

1Biomedical Engineering, University of Wisconsin Madison, Madison, WI, USA; 2Applied Science Laboratory, GE Healthcare, Menlo Park, CA, USA; 3Mathematics, California State University, Fullerton, Fullerton, CA, USA; 4Medical Biophysics, The University of Western Ontario, London, London, Ontario, Canada; 5Applied Science Laboratory, GE Healthcare, Madison, WI, USA; 6Medical Physics, University of Wisconsin Madison, Madison, WI, USA

The noise analysis for three-point decomposition of water and fat was extended to account for the multiple peaks in the spectrum of fat. The Cramer–Rao bound (CRB) was used to study the variance of the estimates of the water images by computing the maximum effective number of signals averaged (NSA) for symmetric and asymmetric echo combination. These theoretical results were verified using NSA computations for 200 water images reconstructed using single peak and multipeak IDEAL reconstruction techniques. Improved separation of water and fat is achieved with the multipeak reconstruction, because of a more accurate modeling of the fat spectrum.

                  2682.     IDEAL at 7T in Mice Using Asymmetric Spin Echo and Gradient Echo Acquisitions

David H. Johnson1, Sreenath P. Narayan1, David L. Wilson1,2, Chris A. Flask1,2

1Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA; 2Radiology, University Hospitals of Cleveland, Cleveland, OH, USA

An IDEAL acquisition based on an asymmetric spin echo acquisition (aSE) was developed for imaging mice on a 7T small animal MRI scanner. A short delay (79us - 790us) was inserted between the refocusing pulse and the readout gradient in a standard spin echo acquisition to introduce fat-water phase shift appropriate for IDEAL estimation of separate fat and water images. The aSE-IDEAL technique generated images with dramatically reduced susceptibility artifacts and improved overall image SNR in comparison to conventional spoiled gradient echo (i.e., FLASH) IDEAL images.

                  2683.     Reduction of Aliasing Artifacts in Diffusion-Weighted PROPELLER Imaging

Novena Rangwala1,2, Girish Srinivasan1,2, Xiaohong Joe Zhou1,3

1Center for Magnetic Resonance Research, University of Illinois Medical Center, Chicago, IL, USA; 2Dept. of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA; 3Depts. of Radiology, Neurosurgery and Bioengineering, University of Illinois Medical Center, Chicago, IL, USA

Diffusion imaging is typically performed in axial planes because of the pronounced image distortion in sagittal and coronal planes using echo planar imaging and increased aliasing artifacts with PROPELLER. We have developed a simple “slice-tilting” technique which reduces the aliasing artifacts in a diffusion-weighted PROPELLER sequence by exciting a slightly different slice than the one selected by the refocusing RF pulses. This technique has resulted in ~60% reduction of streaking artifacts in sagittal and coronal diffusion-weighted images of the human brain, suggesting the possibility of obtaining high quality diffusion images in any arbitrary plane orientation.

                  2684.     Pulse Sequence Programming Using XML and JavaScript

William Overall1, John Pauly1

1Electrical Engineering, Stanford University, Stanford, CA, USA

We have developed a lightweight, interpreted language for specifying MR pulse sequences using XML and JavaScript. In analogy to web programming with HTML and JavaScript, this allows rapid prototyping of pulse sequences that are portable across platforms and easy to modify. This specification was implemented within the SpinBench pulse-programming environment, freely available online.

                  2685.     FLUSTER: A Combined Multiecho Radial/Cartesian Encoded Gradient Echo Sequence for Bone and Soft Tissue Segmentation

Andre Jan Willem van der Kouwe1,2, Thomas Benner1,2, Michael Hamm3, Sonia Nielles-Vallespin4, Bruce Fischl5,6

1Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA; 2Department of Radiology, Harvard Medical School, Brookline, MA, USA; 3Siemens Medical Solutions USA Inc., Charlestown, MA, USA; 4Siemens Healthcare, Erlangen, Germany; 5Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA; 6CSAIL, Massachusetts Institute of Technology, Cambridge, MA, USA

Automated whole head segmentation and bone identification requires various contrasts from the optimized scans used for automated brain morphometry. In particular, imaging bone using MR is challenging. We present a combined multiecho radial/Cartesian encoded spoiled gradient echo sequence that yields several contrasts in a single sequence including an ultrashort FID containing the signature of bone and later components that can be used to identify water and fat and estimate the B0 field offset. Quantitative spin density and T1 relaxation times can also be estimated, using established techniques, if more than one flip angle is collected.

                  2686.     TurboCRAZED BOLD Imaging Detects Specific Activation in the Rat Brain After Somatosensory Stimulation at 16.4 Tesla

David Z. Balla1, Hannes M. Wiesner1, Gunamony Shajan1, Cornelius Faber2, Rolf Pohmann1

1High-Field MR Center, Max-Planck-Institute for Biological Cybernetics, Tuebingen, Germany; 2Department of Experimental Magnetic Resonance, Institute for Clinical Radiology, Muenster, Germany

The TurboCRAZED sequence is based on intermolecular multiple-quantum coherence (iMQC) detection. The provided contrast is weighted by tissue structure and this weighting can be adjusted by modifying one sequence parameter. We employed TurboCRAZED for the first time for stimulation-induced BOLD fMRI in animals. Electrical forepaw stimulation activated only a region in the primary sensory cortex as expected. Technical details of the sequence and the extensive animal monitoring used during the experiments will be discussed.

                  2687.     Ultrafast Blood T1 Mapping with Steady-State Free Precession (SSFP) Imaging

Wen-Chau Wu1, Jiongjiong Wang2

1Graduate Institute of Clinical Medicine, School of Medicine, National Taiwan University, Taipei, Taiwan; 2Radiology and Neurology, University of Pennsylvania, Philadelphia, PA, USA

Conventional T1 measurement is time-consuming as the longitudinal relaxation curve is sampled with varied inversion times in separate scans. TrueFISP is a balanced SSFP technique characterized by high imaging speed while preserving a high signal-to-noise ratio. We observed that blood pool signals in inversion-recovery (IR) prepared TrueFISP acquisitions generally follow the conventional T1 recovery model due to the replenishment of blood spins with longitudinal magnetization unperturbed by the TrueFISP pulse train. By conducting experiments and computer simulations, we demonstrated the feasibility of using multi-phase IR-TrueFISP for fast (< 1 min) and reliable (2% repeatability) in-vivo blood T1 mapping.

                  2688.     Flip Angle Strategies for Multiphase DENSE

Andreas Sigfridsson1, Henrik Haraldsson2, Tino Ebbers2, Shinichi Takase1, Hans Knutsson2, Hajime Sakuma1

1Mie University, Tsu, Mie, Japan; 2Linköping University, Linköping, Sweden

In multiphase DENSE MRI, available signal decreases during the cardiac cycle due to excitation and T1-relaxation. Because of this, a widely used method is to vary the flip angle to yield constant SNR during the cardiac cycle. Unfortunately, this may lead to significant sacrifices of SNR in the early cardiac phases.

                  2689.     Balanced SSFP Cisternography in the Cerebellopontine (CP) Angle: Inconsistent Vessel Contrast and a Possible Remedy

Pei-Hsin Wu1, Chiao-Yuan Lin1, Cheng-Chieh Cheng2, Hsiao-Wen Chung1, Wen-Chau Wu3, Brian A. Hargreaves4, Norbert J. Pelc4

1Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan; 2Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan; 3Department of Clinical Medicine, National Taiwan University, Taipei, Taiwan; 4Department of Radiology, Stanford University, Palo Alto, CA, USA

Cerebellopontine (CP) angle has been an important target for the evaluation of various pathologic processes with bSSFP sequenece. However, inconsistencies of blood signal intensities are observed, hampering clear distinction of the vessels from the nerve roots. Our results suggest that flow along phase encoding direction will affect magnitude profile causing signal loss in blood vessels. Moreover, partial recovery of vessel signals could be achieved by adjusting the flip angle in bSSFP imaging according to the simulation. Consequently, suitable contrast behavior could be achieved with the appropriate flip angle adjustment based on the flow velocity in the region of interest.

                  2690.     Kt-Accelerated Velocity-Encoded Black-Blood MRI for Quantification of Myocardial Motion at 3.0T

Anja Lutz1, Axel Bornstedt1, Vinzenz Hombach1, Robert Manzke2, Volker Rasche1

1Department of Internal Medicine II, University Hospital of Ulm, Ulm, Baden-Württemberg, Germany; 2Philips Research Europe, Hamburg, Germany

Short scan times for velocity-encoded black-blood functional cardiac imaging with good spatial resolution are desirable since patient compliance prohibits excessive scan times. Applying kt-Blast shortens the scan duration and therefore allows acquiring data with better spatial resolution in the same time. An analysis of the myocardial motion was performed and the characteristic velocities determined with and without kt-Blast were compared revealing an agreement of results. Kt-Blast can therefore be used to mitigate the problem of restricted spatial resolution resulting from a limited scan time.

                  2691.     Fast Multislice T2-Weighted Image Assessment of Brain with TIDE BSSFP Imaging

Yin-Cheng Kris Huang1,2, Chun-Jung Juan2, Hing-Chiu Chang3, Hua-Shan Liu2, Teng-Yi Huang4, Hsiao-Wen Chung1,2, Cheng-Yu Chen2, Guo-Shu Huang2

1Department of Electrical Engineering, National Taiwan University, Taipei City, Taiwan; 2Department of Radiology, Tri-Service General Hospital, Taipei City, Taiwan; 3Applied Science Laboratory, GE Healthcare Taiwan, Taipei City, Taiwan; 4Department of Electrical Engineering, National Taiwan University of Scienece and Technology, Taipei City, Taiwan

In clinical routine, TSE is used as the standard T2-weighted imaging sequence. The scan time usually takes several minutes for multislice imaging along either one of the three anatomical orientations (transverse, coronal, and sagittal). Obtaining all these information using TSE is not practical considering the clinical throughput. To achieve this goal, we propose to use the TIDE bSSFP, a sequence shown to carry T2 weighting and intrinsic fat suppression. Its scan time takes only one second for a single slice scan. To evaluate the feasibility, we compared the image quality of TIDE bSSFP with those of FS-T2-TSE and FS-T2-TGSE (GRASE) quantitatively, by means of ROI analysis of the gray and white matters of the brain.

                  2692.     Multimodal MRI Changes in Cortical Grey Matter Following Formalin Fixation

Klaus Schmierer1, Janet R. Thavarajah1, Harold G. Parkes1, David H. Miller1, Daniel J. Tozer1

1Neuroinflammation, Institute of Neurology, UCL, London, England, UK

Post mortem multiple sclerosis (MS) brain is being used to establish the pathological correlates of changes detected using MRI. Fixation of brain tissue introduces a potential confounder that may affect the inference of in vivo changes from MR/histology studies. This study investigated changes following fixation of quantitative MR indices in MS cortical grey matter (CGM). Fixation results in a substantial drop of T1, less so of magnetization transfer ratio, and an increase of macromolecular proton fraction in post mortem MS CGM. These changes are likely due to (i) direct formaldehyde effects and (ii) intra- and intermolecular cross-linking of macromolecules.

                  2693.     Separation of Relaxation Time Constants Through Cylindrical Coordinates

Bahman Tahayori1,2, Leigh Andrea Johnston1,2, Kelvin J. Layton1,2, Peter Mark Farrell1,2, Iven M.Y. Mareels1,2

1Eelectrical and Electronic Engineering Department, The University of Melbourne, Melbourne, Victoria, Australia; 2National ICT Australia, Melbourne, Victoria, Australia

A novel interpretation of magnetic resonance is provided by transferring the Bloch equations to the cylindrical coordinates. It is shown that in this new framework the differences between relaxation processes are easier to understand. From the dynamics of the MR signal in the cylindrical coordinates it is obvious that the two components of the T2* decay rate come from two different sources. It is expected that the new representation of the Bloch equation will allow researchers to revisit the pulse design question as well as finding optimal input to MRI systems.

                  2694.     Effect of RF Pulse Duration on T2 Quantification Using Multi-Echo Spin Echo Sequences

Oliver Bieri1, Klaus Scheffler1

1Division of Radiological Physics, University of Basel Hospital, Basel, Switzerland

Besides spin density, relaxation times (T1,T2) are the most basic intrinsic tissue parameters in MR imaging. Typically, a Carr-Purcell-Meiboom-Gill (CPMG) pulse train is used as a gold standard for T2 quantification of tissues or pathologies of interest. It will be shown that finite RF effects may lead to a general overestimation of the true T2 value of tissues by 5-10% using multi-echo SE sequences.

                  2695.     Bloch Solver Simulation Realization on a Graphics-Processing Unit (GPU)

Silke Maria Lechner1,2, Daniel Butnaru2, Hans-Joachim Bungartz2, Dong Chen1,3, Mika W. Vogel1

1Advanced Medical Applications Laboratory, GE Global Research, Munich, Bavaria, Germany; 2Department of Scientific Computing in Computer Science, Technical University Munich, Munich, Bavaria, Germany; 3Department of Scientific Computations, Technical University Munich, Munich, Bavaria, Germany

We present a fast and flexible Bloch solver implementation on a graphics-processing unit (GPU). Optimization techniques with improved memory allocation, controlled data copying and efficient task utilization yield speed-up times that are 6-12 times faster than conventional realizations or 2-6 times faster than other parallelized approaches. We present existing simulation optimizations and introduce the basic concept of our GPU realization. We illustrate the improved performance and benefit of the chosen optimization techniques based on simulated image acquisition with emphasis on performance and accuracy.

                  2696.     “Constant Repetition Time” Imaging Protocols for High Resolution  Lung Proton MR Imaging in Mice

Magdalena Zurek1, Amine Bessaad1, Katarzyna Cieslar1, Yannick Crémillieux1

1Université de Lyon, CREATIS-LRMN, Lyon, France

The spatial resolution of in vivo lung imaging is limited by motion in thoracic cavity. In order to establish imaging protocol with constant repetition time for mice lung MRI, the potential of two different acquisition approaches, retrospective self gating and signal averaging, were investigated and compared to cardio-respiratory gating acquisition.

                  2697.     Analysis of T1 Weighted Spiral Projection Imaging

Ryan Keith Robison1, James Grant Pipe1

1Keller Center for Imaging Innovation, Barrow Neurological Institute, Phoenix, AZ, USA

Spiral Projection Imaging (SPI) is a fast, versatile 3D data acquisition. It has many potential benefits over Cartesian imaging including flow insensitivity, PROPELLER like motion correction in three dimensions, and a smaller number of required excitations. Unfortunately, as with many other spiral based sequences, SPI is degraded by artifacts from gradient inconsistencies and off-resonance blurring. In this study many of the artifacts seen in T1 weighted spoiled gradient SPI are illustrated and analyzed. Comparisons to similar Cartesian images are shown for phantom and volunteer data.

                  2698.     MP2RAGE Contrast Optimization at 7T and Applications

José Pedro Marques1,2, Tobias Kober1,3, Gunnar Krueger3, Wietske van der Zwaag1,2, Pierre-François van de Moortele4, Rolf Gruetter1,2

1Centre d'Imagerie BioMédicale, CIBM, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland; 2Département de Radiologie, Université de Lausanne, Lausanne, Vaud, Switzerland; 3Advanced Clinical Imaging Technology, Siemens Medical Solutions-CIBM, Lausanne, Vaud, Switzerland; 4CMRR, University of Minnesota, Minneapolis, MN, USA

In this work, the contrast of the MP2RAGE sequence was optimized for brain tissues at 7T. This contrast is fully independent of B1-, T2* and proton density. Following the protocol described on the abstract, it can be made virtually B1+ insensitive and therefore usable to estimate T1. The proposed contrast is suitable for applications such as image segmentation given its ability to separate CSF, GM and WM even in whole brain histograms.

                  2699.     Elimination of Inflow Enhancement by Partial Pre-Saturation in RF Spoiled Imaging

Misung Han1,2, Brian A. Hargreaves1

1Radiology, Stanford University, Stanford, CA, USA; 2Electrical Engineering, Stanford University, Stanford, CA, USA

Spoiled gradient echo sequences eliminate transversal magnetization using RF spoiling and spoiler gradients to provide T1-weighted images. Generally, many RF excitations are required to attain steady-state magnetization levels. Therefore, when unsaturated spins are flowing into the imaging volume, inflow enhancement occurs at entry slices of the slab. We show that by applying partial pre-saturating of the flowing spins, a uniform signal profile can be provided within the imaging slab, with the same contrast as stationary spins. We verified this by magnetization simulation, flow phantom experiments, and in vivo experiments in carotid arteries.

                  2700.     Measuring the Cerebro-Spinal Fluid Temperature Using Diffusion MRI

Zoltan Nagy1, Lajos R. Kozak2, Marta Bango3, Miklos Szabo3, Rudas Gabor2, Zoltan Vidnyanszki2

1Wellcome Trust Centre for Neuroimaging, University College London, London, UK; 2Szentagothai J. Knowledge Centre, MR Research Centre, Semmelweis University, Budapest, Hungary; 3First Department of Pediatrics, Semmelweis University, Budapest, Hungary

While hypothermia is used as a neuroprotective method after stroke, cardiac arrest or traumatic brain injury, and elevated body temperature increases the risks of convulsions and worsening of brain injury. However, in clinical practice the actual brain temperature in these cases is either estimated indirectly from measurements elsewhere in the body or with invasive methods. We developed a protocol which is based on diffusion weighted MRI to estimate the temperature of the CSF within the lateral ventricles of the brain. Knowledge of the brain temperature may improve the protocols for induced hypothermia in patients.

                  2701.     Increasing Strain Accuracy in Strain-Encoded (SENC) Imaging Using Center-Of-Mass Method

Jakir Hossain1, Tamer Basha1, Nael F. Osman1,2, Michael A. Jacobs2

1ECE, Johns Hopkins University, Baltimore, MD, USA; 2Radiology, Johns Hopkins University

: An effective post-processing method used to compute a strain distribution or strain map from acquired Strain Encoded (SENC) imaging is the center-of-mass method. This article presents a novel approach to improving this method in order to produce a more accurate strain map used for detection of stiff masses in soft tissues.

                  2702.     Dixon BSSFP in the Presence of Bo Inhomogeneities

Michel Louis Lauzon1,2, Randall Brooke Stafford2,3, Mohammad Sabati4, Richard Frayne1,2

1Radiology, University of Calgary, Calgary, AB, Canada; 2Seaman Family MR Research Centre, Foothills Medical Centre, Calgary Health Region, Calgary, AB, Canada; 3Physics and Astronomy, University of Calgary, Calgary, AB, Canada; 4Radiology, University of Miami, Miami, FL, USA

The two-point, fat/water-separation Dixon method for balanced steady-state free precession introduced by Huang et al shows great promise for non contrast-enhanced MRA applications. Here, we investigate its limitations in the presence of Bo inhomogeneities (i.e., from magnet non-uniformity, susceptibility, etc.), and for pixels containing a mixture of fat and water. From the analysis, we propose acquiring and using a Bo inhomogeneity map to better suppress fat and produce more robust water-only images.

                  2703.     K-Space Point Mapping in the Presence of Inhomogeneous Magnetic Fields for Mobile MR

Toni Michael Drießle1, Florian Fidler2, Michael Ledwig2, Stefan Wintzheimer2, Daniel Gensler3, Peter Michael Jakob2,3

1Dept. of Experimental Physics 5, University of Würzburg, Würzburg, Frankonia, Germany; 2MRB, Research Center Magnetic-Resonance-Bavaria, Würzburg, Germany; 3Dept. of Experimental Physics 5, University of Würzburg, Würzburg, Germany

Topic of this study was the developement of a k-space mapping method usable in inhomogeneous magnetic field, commonly found in mobile MR applications. Due to weight limitations in mobile MR inhomogeneities of the magnetic field are a common problem.

                  2704.     Off-Resonance MRI for Detecting T1 Changes Around Metallic Implants

Wilfred Wing-Kay Lam1, Angus Zoen Lau1,2, Charles Henry Cunningham1,2

1Imaging Research, Sunnybrook Health Sciences Centre, Toronto, ON, Canada; 2Dept. of Medical Biophysics, University of Toronto, Toronto, ON, Canada

Detection of prosthetic joint infection is done with radionuclide imaging and cannot be done with conventional MR because of signal dephasing in the magnetic field of the metallic implant. We show that T1 measurements using off-resonance excitation and defocusing can be made close to the implant and has the potential to detect T1 changes in tissue from prosthetic joint infection. The T1 shortening caused by 2 mm-thick CuSO4-doped agar layers on the implant was measured at the off-resonance frequencies 2000 Hz above and 1500 Hz below the resonance frequency of water in 500 Hz steps.

                  2705.     Comparison of Dixon Methods for Fat Suppression in Single Breath-Hold 3D Gradient-Echo Abdominal MRI

Holger Eggers1, Bernhard Brendel1, Gwenael Herigault2

1Philips Research Europe, Hamburg, Germany; 2Philips Healthcare, Best, Netherlands

Dixon methods have been demonstrated to provide a robust fat suppression in abdominal imaging. To achieve adequate coverage and spatial resolution in a single breath-hold, scan efficiency plays a crucial role in this application. Four Dixon methods, including a new one, are compared in this work regarding their scan efficiency. Constraints on the used echo times are found to be at least as limiting as the minimum number of echo times. The new method, which relaxes constraints of existing two-echo methods, is shown to allow an acceleration of protocols by up to 40%.

                  2706.     Iterative Fat-Water Separation in Steady State with Dedicated MRI Systems

Luca Balbi1, Jochen Leupold2, Marco Vicari1

1MRI R&D, Esaote S.p.A., Genoa, Italy; 2Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany

Low-field dedicated MR tomographs are an interesting compromise between management costs and diagnostics requirements, above all when provided with modern MRI techniques, potentially benefiting of the reduced T1 value with respect to high-field. An example of such techniques is a 'Dixon'-like iterative fat-water separation post-processing of MRI data acquired by means of SSFP multi-echo sequences. This is indeed a fruitful union allowing to choose proper echo times to reduce possible inhomogeneity-induced artifacts, leading to an appreciable SNR efficiency and, above all, providing a strong diagnostic impact. Very promising results are shown, obtained by a 3D three-echo SSFP-FID sequence on a phantom consisting of a vacuum-sealed packed swine bacon.

                  2707.     Validation of Fat Quantification with T2* Correction and Accurate Spectral Modeling in a Novel  Fat-Water-Iron Phantom

Catherine DG. Hines1, Huanzhou Yu2, Ann Shimakawa2, Charles A. McKenzie3, Venkata V. Chebrolu1, Jean H. Brittain4, Scott B. Reeder1,5

1Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA; 2Applied Science Laboratory, GE Healthcare, Menlo Park, CA, USA; 3Medical Biophysics, University of Western Ontario, London, Ontario; 4Applied Science Laboratory, GE Healthcare, Madison, WI, USA; 5Radiology, University of Wisconsin-Madison, Madison, WI, USA

Accurate quantification of fat with MRI requires phantoms with accurately known mixtures of water and fat for the development and validation of new MRI methods that correct for confounding factors such as T2* and the complex spectrum of fat. Construction of a novel phantom containing controlled, homogeneous amounts of fat, water, and iron is described, and used to validate chemical shift based fat-water separation methods of fat quantification that correct for T2* and use accurate spectral modeling of fat. Results demonstrate the accuracy and utility of the designed phantom and excellent correlation of imaging fat-fractions to known fat-fractions.

                  2708.     Influence of Relaxation on Fat Suppression by Dixon Methods in Musculoskeletal MRI

Holger Eggers1, Peter Boernert1, Clemens Bos2

1Philips Research Europe, Hamburg, Germany; 2Philips Healthcare, Best, Netherlands

Prospective chemical shift-based fat suppression methods typically show between 5% and 10% leakage of fat into water signal. Especially in musculoskeletal imaging, where short relaxation times occur, Dixon methods may produce higher leakage. It is demonstrated in this work that it may be reduced to at least the level attained with prospective methods by an appropriate choice of the echo spacing and the number of echoes. Alternatively, relaxation may be included in the signal model employed for the separation. Detailed knowledge of the fat spectrum is found to be unnecessary to reach this goal.

                  2709.     Ultra-Low SAR MR Imaging of the Brain at 1.5 Tesla

Subhendra Nath Sarkar1, Ananth Madhuranthakam2, David Alsop1, Neil Rofsky1, Reed Busse3, Rafeeque Bhadelia1, Efstathios Papavassiliou4, David Hackney1

1Radiology, Beth Israel Deaconess Medical Center, Boston, MA, USA; 2Applied Science Laboratory, GE Healthcare, Boston, MA; 3Applied Science Laboratory, GE Healthcare, Madison, WI; 4Neurosurgery, Beth Israel Deaconess Medical Center, Boston, MA, USA

Implants including pacemakers often present routine MRI contraindications due to tissue heating. Device manufacturers sometimes issue guidelines reducing risks for these patients. Since these restrictions reduce quality or eliminate MRI altogether, we explored the limits to which SAR can be lowered using a modified 3D FSE sequence and optimized the refocusing pulse trains. Isotropic 3D T2 and FLAIR acquisitions with SNR and CNR comparable to clinical quality were achieved for brain imaging with SAR 100x lower than current practice. This minimizes the risk involved with high SAR and may offer MRI options to currently contraindicated patients with implants and pacemakers.