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

Jordan L. Hovdebo¹, Lawrence Ryner^1,2

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 Ozhinsky^1,2, Sarah J. Nelson^1,3

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 Adalsteinsson^1,3

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 Chung^1,2, 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 Dreher^1,2, Ekkehard Küstermann^1,2, Dieter Leibfritz^1,2

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 Chen^1,2, 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 Yahya^1,2, B. Gino Fallone^1,2

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. Mareci^2,3, Nicholas E. Simpson^4,5

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.

                  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 Gruetter^1,2

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 Dimitrov^1,2, 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 T_ct 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 Dahlquist^1,2, Eva Lund¹, Peter Lundberg^1,2

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 Dimitrov^1,2, 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 Snyder^1,2, Richard B. Thompson³, Alan H. Wilman^2,3

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. Miller^1,2, Peter C. Williamson^2,3, Dick J. Drost^1,2

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 Dimitrov^1,2, 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 Sheffield^1,2, Michael D. Noseworthy^2,3, John Bienenstock^2,4

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 Wijtenburg^1,2, Jack Knight-Scott^1,2

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.

                  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 Leung^1,2, Albert P. Chen³, Angus Z. Lau^1,2, Wilfred W. Lam², Charles H. Cunningham^1,2

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 Mayer^1,2, Yi-Fen Yen³, James Tropp⁴, Ralph E. Hurd³, Adolf Pfefferbaum^2,5

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 Keshari^1,2, 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. Witney^1,2, Roberta Napolitano^1,3, Mikko I. Kettunen^1,2, Ferdia A. Gallagher^2,4, Kevin M. Brindle^1,2

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. Cunningham^1,2, 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 Harrison^1,2, A Dean Sherry^3,4, Craig R. Malloy^5,6, Matthew E. Merritt^7,8

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 Gallagher^1,2, Mikko I. Kettunen^2,3, Rebekah L. McLaughlin^2,3, De-en Hu^2,3, Tim H. Witney^2,3, Jan H. Ardenkjaer-Larsen⁴, Kevin M. Brindle^2,3

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 Leung^1,2, Wilfred W. Lam¹, Albert P. Chen³, Charles H. Cunningham^1,2

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 Gallagher^1,2, Mikko I. Kettunen^2,3, De-en Hu^2,3, Sam E. Day^2,3, Magnus Karlsson⁴, Anna Gisselsson⁴, Mathilde H. Lerche⁴, Kevin M. Brindle^2,3

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 Gamliel^1,2, Hyla Allouche-Arnon^1,3, Ruppen Nalbandian^1,3, 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-Arnon^1,2, Ayelet Gamliel^3,4, Ruppen Nalbandian^3,5, 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. Chan^1,2, 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. Chekmenev^1,2, 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 ~(γ_1H/γ_X) 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. Chekmenev^1,2, 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. Tran^1,2, Henry R. Chan^1,2, Johnathan Chou¹, Shawn Wagner¹, Pratip Bhattacharya^1,2, Brian D. Ross^1,2

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. Walsworth^2,3, 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. Rosen^1,2, Ronald L. Walsworth^1,2, 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 Denisov^1,2, Arnaud Comment^3,4, Paul Vasos⁵, Sami Jannin⁴, Jacques van der Klink⁴, Riddhiman Sarkar⁵, Geoffrey Bodenhausen⁵, Helene Hall¹, Deniz Kirik^1,2

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 Kurdzesau^2,3, Cristina Cudalbu¹, Arnaud Comment^1,2, Jacques J. van der Klink², Gil Navon⁴, Rolf Gruetter^1,5

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.

                  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 Mintzopoulos^2,3, Meenu Kesarwani^2,4, Valeria Righi^2,3, Laurence G. Rahme^2,5, Harold M. Swartz¹, A Aria Tzika^2,3

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.

                  2482.     μMRI Optimisation for Phenotyping the Embryo Mouse Heart

Jon Orlando Cleary^1,2, Anthony Nathan Price¹, David L. Thomas^2,3, Peter J. Scambler⁴, Vanessa Kyriakopoulou⁴, Roger J. Ordidge^2,3, 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 Lee^1,2, Jeremy J. Flint^2,3, Lisa Guay-Woodford⁴, Stephen J. Blackband^3,5

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. Bray^1,2, Mark Filiaggi³, Chris V. Bowen^1,4, Steven D. Beyea^1,4

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 Huang^1,2, 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 Huang^1,2, Guangping Dai², Alexei Bogdano³, Bruce R. Rosen^1,2, 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 Huang^1,2, Dmitriy Atochin³, Guangping Dai², Alexei Bogdano⁴, Paul L. Huang³, Bruce R. Rosen^1,2, 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. Loveless^1,2, Anthony Z. Faranesh³, John C. Gore^1,2, Thomas E. Yankeelov^1,2

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. Macgowan^1,2, Shengping Wu², Rogerio Tessler³, Jaques Belik^2,4, Andrea Kassner^2,5

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 Christen^1,2, Nicolas Joudiou^1,2, Nicolas Pannetier^1,2, Sebastien Reyt^1,2, Christoph Segebarth^1,2, Chantal Rémy^1,2, Emmanuel L. Barbier^1,2

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.

                  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. Brock^1,2

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 Suga^1,2, 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.

                  2509.     Reimbursement for Magnetic Resonance Spectroscopy

Alexander Peter Lin^1,2, 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.

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

Charles Mougenot^1,2, Max O. Köhler³, Bruno Quesson², Ari Partanen³, Julia Enholm³, Chrit T. Moonen², Teuvo Vaara³, Gösta J. Ehnholm^3,4

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 Mougenot^2,3, 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 Kaye^1,2, Jing Chen^1,2, 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 Bystritsky^1,2, 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.

                  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 Fain^1,3

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. Rea^1,2, Zion Tse², Veronica Morgan³, Sharon Giles³, Donald W. McRobbie^1,3, 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 Nordbeck^1,2, 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 Woloschak^3,4, Reed Omary^1,4, Andrew Larson^1,4

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 Deng^1,2, Sumeet Virmani¹, Richard A. Tang¹, Guang-Yu Yang³, Gayle Woloschak^1,4, Reed A. Omary^1,5, Andrew C. Larson^1,5

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 Schulz^1,2, 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. Block^1,2, Scott B. Reeder^1,3

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 Immel^2,3, 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 Unal^1,2, 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. Brodsky^1,3, 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. Wright^1,2

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 Saybasili^1,2, 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.

                  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. Curtis^1,2, Christopher K. Anand³, Craig K. Jones¹, L Martyn Klassen¹, Ravi S. Menon^1,2

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 Jankiewicz^1,2, Huairen Zeng^1,2, Adam W. Anderson^1,3, Malcolm J. Avison^1,3, E Brian Welch^1,4, John C. Gore^1,3

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 Park^1,2

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 Bartha^2,3, 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 Hurley^1,2, 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 Sekino^1,2, 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 Liu^1,2, 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 Welch^1,2, 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 Chen^1,2, 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.

                  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 Nordell^1,2, Stefan Skare^2,3

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. Jakob^1,3

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 Gabr^1,2, 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 Welch^1,2, 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 Jakob^1,3

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 McKenzie^1,5

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 Dittrich^1,2, 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 Kim^1,2

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 Visser^1,2, 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 Roux^1,2

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. Dortch^1,2, Adam R. Horch^1,2, Mark D. Does^1,2

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 Wagner^1,2, Pratip Bhattacharya¹, Brain D. Ross^1,2

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 Wu^1,2, Jyh-Horng Chen^2,3, 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.

                  2679.     3D Isotropic Brain Imaging Using Wideband MRI

Edzer Lienson Wu^1,2, Tzi-Dar Chiueh³, Jyh-Horng Chen^2,3

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 Wu^1,2, Kuan-Hung Cho^2,3, Tzi-Dar Chiueh³, Jyh-Horng Chen^2,3

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. Wilson^1,2, Chris A. Flask^1,2

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 Rangwala^1,2, Girish Srinivasan^1,2, Xiaohong Joe Zhou^1,3

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 Kouwe^1,2, Thomas Benner^1,2, Michael Hamm³, Sonia Nielles-Vallespin⁴, Bruce Fischl^5,6

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 Huang^1,2, Chun-Jung Juan², Hing-Chiu Chang³, Hua-Shan Liu², Teng-Yi Huang⁴, Hsiao-Wen Chung^1,2, 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 Tahayori^1,2, Leigh Andrea Johnston^1,2, Kelvin J. Layton^1,2, Peter Mark Farrell^1,2, Iven M.Y. Mareels^1,2

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 Lechner^1,2, Daniel Butnaru², Hans-Joachim Bungartz², Dong Chen^1,3, 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 Marques^1,2, Tobias Kober^1,3, Gunnar Krueger³, Wietske van der Zwaag^1,2, Pierre-François van de Moortele⁴, Rolf Gruetter^1,2

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 Han^1,2, 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. Osman^1,2, 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 B_o Inhomogeneities

Michel Louis Lauzon^1,2, Randall Brooke Stafford^2,3, Mohammad Sabati⁴, Richard Frayne^1,2

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 Jakob^2,3

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 Lau^1,2, Charles Henry Cunningham^1,2

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. Reeder^1,5

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.