Pulse Sequences

13:30         3058.     Whole Orbit Soft Tissue Deformation Acquired by Accelerated 3D CSPAMM Tagging During Eye Motion

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Marco Piccirelli¹,², Andrea Kaspar Rutz¹, Oliver Bergamin², Peter Boesiger¹, Roger Luechinger¹

¹University and ETH Zurich, Zurich, Switzerland; ²University Hospital Zurich, Switzerland

In complex orbital mechanical disorders, a better comprehension of ocular motion dynamic is needed. The deformation pattern within extraocular muscles (EOM) and orbital connective tissues has not been understood yet. In this work, an accelerated truly three-dimensional tagging acquisition method is proposed enabling the assessment of motion information with whole orbit coverage in a scantime allowing good motion reproducibility. A reduced field-of-view method was incorporated and 3D data sets were acquired sequentially with line tag preparation in each of the three spatial dimensions. Data were post-processed with 3D peak-combination HARP. Tissues within the orbit could be reliably tracked and characterized.

14:00         3059.     Orthogonal TrueFISP Acquisitions Using Paired Reverse Centric Phase Encoding

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Jamal Jon Derakhshan¹,², Mark A. Griswold¹,², Jeffrey L. Sunshine², Jeffrey L. Duerk,¹²

¹Case Western Reserve University, Cleveland, Ohio, USA; ²University Hospitals Case Medical Center, Cleveland, Ohio, USA

Paired reverse centric phase encoding is presented as a way to eliminate saturation banding in interleaved orthogonal TrueFISP imaging. Simulation results demonstrate significant (> 2x) reduction of orthogonal plane saturation artifacts across various base resolutions, flip angles and tissue types. Phantom imaging demonstrates the ability to eliminate both saturation and eddy current artifacts by pairing the reverse centric lines. Human in vivo abdominal scout imaging demonstrates the utility of the new acquisition strategy. Application to interventional MRI is demonstrated by presenting three orthogonal images acquired during real-time guidance of an RF electrode to the porcine adrenal gland in vivo.

14:30         3060.     Artifact-Free Stimulated-Echo Acquisition Mode (STEAM) Cardiac Images with Improved Signal-To-Noise Ratio (SNR)
[Not Available]

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Tamer A. Basha¹, ElSayed H. Ibrahim¹, Nael F. Osman¹

¹Johns Hopkins University, Baltimore, Maryland, USA

The stimulated echo acquisition mode (STEAM) is currently used in a wide range of applications for imaging tissue parameters. However, when applying STEAM in cardiac imaging, signal loss of the myocardium has been reported due to the intravoxel dephasing of the magnetization during the contraction (or stretching) of the cardiac muscle. Despite of its intrinsically low SNR, STEAM was quite appealing for the assessment of various cardiac functions. In this work, we deal with the SNR and deformation artifactproblems in STEAM technique. First, we introduce a SSFP acquisition technique to increase the SNR then we propose a method for removing the deformation artifacts from the STEAM images.

15:00         3061.     Investigation of Relationship Between Applied Current Amplitude and Measured Current Density Magnitude in a Live Pig

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Tim P. DeMonte¹, Jia-Hong Gao², Dinghui Wang³, Weijing Ma³, Michael L.G. Joy³

¹Field Metrica Inc., Toronto, Canada; ²University of Chicago, USA; ³University of Toronto, Canada

Current density imaging is an MRI technique used to measure current density vectors in tissue.  Human electro-muscular incapacitation (HEMI) devices are becoming commonly used by law enforcement and military.  The ultimate goal of this work is to achieve better understanding of the effects of HEMI on physiology for enhancement of efficacy and safety.  Specifically, the relationship between applied current amplitude and measured current density magnitude is investigated.  This relationship is expected to be linear over small ranges, but not well understood for larger ranges.  A small range is investigated in an in-vivo pig to establish a method for future work.

New Contrasts & Quantitation

13:30         3062.     Dark Blood BSSFP Imaging Using Magnetization Prepared Random Velocity Encoding

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Jamal Jon Derakhshan¹,², Mark A. Griswold¹,², Jeffrey L. Sunshine², Jeffrey L. Duerk,¹²

¹Case Western Reserve University, Cleveland, Ohio, USA; ²University Hospitals Case Medical Center, Cleveland, Ohio, USA

A new method for generating steady state, short TR, dark blood bSSFP images based on magnetization prepared TrueFISP is presented. Periodically, the magnetization is returned to the z axis with an α/2 pulse. Thereafter, magnetization preparation includes randomly scaled velocity encoding, similar to RF-spoiling. Simulations demonstrate that flowing blood signal can be reduced by > 95% while stationary tissue undergoes much lower loses (~ 24%) based on T2 decay. Phantom imaging results demonstrate stationary and flowing signals consistent with predictions. Human in vivo imaging demonstrates the ability to null blood flow in a short TR magnetization prepared Cartesian bSSFP sequence.

14:00         3063.     Enhanced Contrast in CEST MRI Via Intermolecular Double Quantum Coherences

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Shengchun Zhang¹, Huijun Sun¹, Zhong Chen¹, Congbo Cai¹, Jianhui Zhong²

¹Xiamen University, Xiamen, People's Republic of China; ²University of Rochester, Rochester, New York, USA

A CEST imaging technique based on intermolecular double quantum coherence (iDQC) is proposed. Quantitative analysis and experiments in glucose agarose-gel phantoms demonstrate that, in CEST MRI, iDQC signal is more sensitive to RF saturation than the conventional SQC signal, and thus needs RF saturation pulses of lower power to achieve similar CEST image contrast. Consequently, the method can reduce the potential RF burning in clinic applications, and is expected to facilitate the study of the CEST effect in the system with exchangeable protons of low concentrations.

14:30         3064.     An Investigation of Optimizing and Translating Pulsed-Chemical Exchange Saturation Transfer (CEST) Imaging to a 3 T Clinical Scanner [Not Available]

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Phillip Zhe SUN¹, Thomas Benner¹, Gregory Sorensen¹

¹A. A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, USA

Chemical exchange saturation transfer (CEST) MRI provides a sensitive detection mechanism that allows characterization of dilute labile protons usually undetectable by MRI. Particularly, amide proton transfer (APT) imaging, a variant of CEST MRI, has been shown capable of detecting ischemic tissue acidosis, and may serve as a surrogate metabolic imaging marker. For pre-clinical CEST imaging, long continuous-wave (CW) RF irradiation is often applied so that the steady state CEST contrast can be reached. On clinical scanners, however, specific absorption rate (SAR) limit and hardware design preclude the use of CW irradiation, and instead require an irradiation scheme of repetitive RF pulses (pulsed-CEST imaging). In this work, CW- and pulsed-CEST MRI were systematically compared using a tissue-like pH phantom on an imager capable of both CW and pulsed RF irradiation schemes. The results showed that the maximally obtainable pulsed-CEST contrast is about 95% of CW-CEST contrast, and their optimal RF irradiation powers are equal. Moreover, the pulsed-CEST imaging sequence was translated to a 3 Tesla scanner and detected minor pH difference of 0.6 pH unit using exchangeable amine groups (1.9 ppm). Furthermore, pilot endogenous pulsed-APT imaging of control human volunteers was demonstrated, warranting future APT MRI of stroke patients to fully elucidate its diagnostic value.

15:00         3065.     Relaxometry Changes in a Gel Dosimetry Phantom Due to Continued RF Exposure

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Gary Paul Liney¹, Mark Godber², Andrew D. Wilson², John W. Goodby³

¹University of Hull, Hull, UK; ²University of York, York, UK; ³University of York, York, UK

To quantify changes in transverse relaxometry, in phantoms used for MRI gel-dosimetry, due to continued RF heating in the scanner, and to map the distribution of these effects.

13:30         3066.     B₁ Correction for Improved Bound Pool Fraction Maps

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Nikola Stikov¹, Robert F. Dougherty¹, John Mark Pauly¹

¹Stanford University, Stanford, California , USA

The bound pool fraction (f) is an indicator of myelin content in the brain, and cross-relaxation imaging is an efficient method of mapping the f parameter in vivo.  The first step in cross-relaxation imaging is obtaining an accurate T₁ map of the brain, but B₁ inhomogeneity makes this task difficult.  We incorporated B₁ correction in our cross-relaxation procedure, and scanned three subjects with and without this correction.  Our procedure removed variations in the T₁ values of white matter across subjects, while reducing the total cross-relaxation scan time.

14:00         3067.     FISPCEST: A Rapid, Acquisition for Dynamic Detection of CEST/PARACEST Activity

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Tejas Shah¹,², Meser Ali¹, Guanshu Liu¹, Mark D. Pagel¹, Chris A. Flask¹

¹Case Western Reserve University, Cleveland, Ohio, USA

We have developed a new FISP Chemical Exchange Saturation Transfer (FISPCEST) pulse sequence to sensitively detect effects. The FISPCEST technique provides <3sec acquisition times which is an order of magnitude less than current CEST techniques. The FISPCEST acquisition combines a single, ~2sec, nonselective CEST preparation and a ~500ms FISP acquisition. The improved temporal resolution is obtained with only a 15% loss in CEST sensitivity in comparison to a spin echo CEST acquisition. The FISPCEST acquisition is adaptable to both endogenous and exogenous (PARA)CEST applications and enables the acquisition of CEST spectra maps and/or multislice CEST images in under 1 minute.

14:30         3068.     Tissue-Dependent Asymmetries in the SSFP Off-Resonance Profile

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Karla L. Miller¹, Daniel P. Bulte¹, Gwenaelle Douaud¹, Peter Jezzard¹

¹Oxford University, Oxford, UK

The SSFP signal is strongly sensitive to off-resonance, with a signal profile for an isochromat population that is theoretically symmetric about the tissue frequency ("on-resonance"). However, the existence of frequency-shifted compartments may lead to an asymmetric profile. We demonstrate this asymmetric response for tissues in the brain, finding a strongly asymmetric response in white matter, a moderately asymmetric response in gray matter and an approximately symmetric response in CSF. This response profile may be useful as a novel marker for tissue content.

15:00         3069.     Dynamic Nuclear Polarization Using a Low Field Multi-Channel MR System

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Eugeny Krjukov¹, Martyn Paley¹

¹University of Sheffield, Sheffield, UK

Dynamic nuclear polarisation has been investigated with the free radical carbomyl-PROXYL using a low frequency (360kHz) multi-channel MR system. Enhancement factors of up to 40 were found with 50W or ESR irradiation at 220MHz.

13:30         3070.     Contrast Enhancement by Feedback-Enhanced MRI

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Sophia Y. Yang¹, Dennis W. Hwang¹, Susie Y. Huang², Lian-Pin Hwang³, Yung-Ya Lin¹

¹UCLA, Los Angeles, California , USA; ²Harvard Medical School, Boston, Massachusetts, USA; ³National Taiwan University, Taipei, Taiwan

Feedback-enhanced MRI yields robust image contrast that is sensitive to small differences in the underlying microscopic frequency distributions. Important applications of this method include improving the visualization of SPIO nanoparticles through generation of positive contrast and distinguishing small changes in microscopic susceptibility corresponding to tumor and normal tissue. Using an external electronic device can significantly enhance the feedback field and open opportunities for the design of novel imaging pulse sequences in which the feedback interaction is controllable. Examples of in vitro and in vivo tumor detection in human brain tissue and mouse models of lung adenocarcinoma with active feedback will be demonstrated.

14:00         3071.     MRI Manometry Using Gas Filled Microbubbles Exhibiting High Membrane to Gas Synergy: Towards Clinical Relevance

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Robert Henry Morris¹, Martin Bencsik¹, Marie-Pierre Krafft², Gilles Waton², Nikolaus Nestlé³, Petrik Galvosas⁴, Anil Vangala, Yvonne Perrie⁵

¹Nottingham Trent University, Nottingham, UK; ²Institut Charles Sadron, Strasbourg, France; ³BASF Aktiengesellschaft, Ludwigshafen, Germany; ⁴University of  Leipzig, Leipzig, Germany; ⁵Aston Universit

MRI manometry is performed in vitro using two alternative contrast agents comprised of compressible microcapsules suspended in a liquid medium presenting high viscosity with little reduction of the diffusion coefficient compared to that of bulk water. The currently available contrast agent utilising standard lipid coated gas microcapsules is shown to be highly unstable in typical clinically relevant pressure conditions, whilst perfluorinated gas microcapsules coated with a perfluoroalkylated lipid will allow in vivo measurements in the future.

14:30         3072.     Visualization of Viscoelastic Properties by Combining US Pulses and MRI

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Ole Benjamin Oehms¹, Marcus Radicke¹, Sarah Wrede¹, Meinert Lewerenz¹, Andre Engelbertz¹, Karl Maier¹

¹Friedrich Wilhelms Universität, Bonn, Germany

The irradiation of Ultrasound Pulses (30 ms, at 10 MHz) into a sample during a diffusion sensitive MRI sequence leads to signal changes in liquids and tissue. They are caused by the decrease of the acoustic radiation pressure due to damping of the sound wave which leads to a movement in a liquid along the path of sound propagation. This movement leads to a dephasation if it occurs while the diffusion gradient is active which results in a signal diminishment in that region. This diminishment depends on the viscoelastic properties of the sample. First measurements on Water and Glycerine and on a piece of tissue will be presented in the talk.

15:00         3073.     MR Imaging of Transient Shear Waves Induced by Ultrasonic Radiation Force

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Remi Souchon¹, Rares Salomir¹, Olivier Beuf², Denis Lyonnet³, Jean-Yves Chapelon¹, Olivier Rouviere³

¹INSERM U556, Lyon, France; ²CNRS UMR 5220, Lyon, France; ³Hospices Civils de Lyon, France

This study reports preliminary wave images and temperature measurements for transient MR elastography (MRE) using ultrasound radiation force. Our initial data suggest that an EPI MRE sequence is likely to provide elasticity images while ensuring patient safety.

13:30         3074.     Improved MREIT Reconstruction Using Sodium MRI

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Mark Jason Hamamura¹, L Tugan Muftuler¹, Orhan Nalcioglu¹

¹University of California, Irvine, California , USA

In magnetic resonance electrical impedance tomography (MREIT), electrical currents are injected into an object and the resulting magnetic flux density distribution measured using MRI.  These MRI measurements are then used to reconstruct the conductivity distribution within the object.  In this study, we investigated the incorporation of sodium MRI data into the MREIT reconstruction algorithm.  The results demonstrate that this incorporation can improve the accuracy of the reconstructed conductivity maps.

14:00         3075.     SPIO Acid Dissolution Kinetics with MR Susceptometry

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Ludovic de Rochefort¹, Yi Wang¹

¹Weill Medical College of Cornell University, New York, New York, USA

Superparamagnetic iron oxides benefit from a very strong magnetic moment at low field due to their superparamagnetic property. Here, we show the feasibility of monitoring chemical reaction of SPIO dissolution by acids with MRI. The magnetic moment destruction is measured continuously as a function of time with MR susceptometry.

14:30         3076.     A Quantitative Approach of Extracting Magnetic Moments in Small Cylindrical Object

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Ching-Yi Hsieh¹, Yu-Chung Norman Cheng¹, Jaladhar Neelavalli¹, E. Mark Haacke¹

¹Wayne State University, Detroit, USA

Our goal is to quantify magnetic moments of a small in-vivo object such as veins in the brain from MR images, without any a priori information. By summing up MR signals within three concentric circles, the magnetic moment of the object obtained from different complex data in the same image can be accurate within 10% of its true value. To achieve this accuracy, a long echo time may be needed. The simulations and experimental results are presented for the gel phantom. The agreement between these two results indicates a promising potential of this method.

15:00         3077.     In Vivo T₁ρ-Weighted MR Imaging of Rat Brain Using a Surface Coil at 11.7 Tesla

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Su Xu¹, Jehoon Yang¹, Jun Shen¹

¹National Institute of Mental Health, Bethesda, Maryland, USA

A sech-based adiabatic spin-lock pulse sequence to obtain T _1ρ-weighted MR images using a surface transceiver coil was optimized for enhancing tissue contrast. The utility of this technique was demonstrated using in vivo rat brains after focal bicuculline administration and an 11.7 Tesla 89 mm bore vertical microimager. Signal intensity of the lesion in the T _11ρ-weighted images was significantly elevated 50 minutes after administration of bicuculline.

13:30         3078.     Magnetization-Prepared Shells for Efficient T1-Weighted Brain Imaging

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Yunhong Shu¹, Matthew A. Bernstein¹

¹Mayo Clinic College of Medicine, Rochester, Minnesota, USA

To maximize the contrast in MP-RAGE brain imaging, it is desirable to select a k-space acquisition order that can sample the center of k-space compactly during the peak contrast difference between WM and GM during the inversion recovery curve. The shells trajectory is a non-Cartesian 3D trajectory with high acquisition efficiency and an inherent centric nature. It provides the flexibility required to synchronize the acquisition of the center of k-space to the contrast maximum contrast. Here we theoretically and experimentally demonstrate the feasibility of combining magnetization preparation with the shells trajectory to achieve T1-weighted brain imaging efficiently.

14:00         3079.     Flow-Independent T2-Prepared Inversion Recovery Black Blood MR Imaging

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Chia-Ying Liu¹,², Oliver Wieben¹, Jean H. Brittain², Scott Brian Reeder¹

¹University of Wisconsin-Madison, Madison, Wisconsin, USA; ²GE Healthcare, Madison, Wisconsin, USA

Black blood prepared MRI is used extensively for cardiac and atherosclerotic plaque imaging. Most black blood sequences employ double inversion recovery, which relies on the inflow of nulled blood. As a result, double IR methods are less effective in the presence of slow flow and in-plane flow. We present a new black-black preparation scheme which employs a T2-prepared sequence in combination with an inversion recovery pulse (T2Prep-IR). Excellent blood suppression independent of flow was demonstrated in the heart and carotid arteries of volunteers.

14:30         3080.     In Vivo Blood T1 Mapping Using Inversion Recovery TrueFISP

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Wen-Chau Wu¹, Jiongjiong Wang¹

¹University of Pennsylvania, Philadelphia, USA

In the present study, we demonstrated the feasibility of in vivo blood T1 mapping with an inversion recovery (IR) TrueFISP sequence. The IR TrueFISP signal has been shown to vary with the flip angle, T1 and T2 of static tissue of interest. With continous inflow of flesh blood with undisturbed longitudinal magnitization, the IR TrueFISP curve of blood pool signal approximated standard T1 relaxation. The estimated blood T1 values at 3.0T match well with literature results with minimal sensitivity to variations in flip angle.

15:00         3081.     Practical Optimum Experimental Designs for Fast T1 Relaxometry with SPGR Sequences

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Alexey Samsonov¹, Andrew L. Alexander¹, Youngkyoo Jung¹, Aaron S. Field¹

¹University of Wisconsin, Madison, Wisconsin, USA

Knowledge of the longitudinal relaxation time T1 is required in many quantitative MRI applications.  T1 mapping using variable flip angle SPGR acquisitions is an attractive choice due to its speed.  In this work, we describe a method for automatic selection of T1 mapping flip angles, which explicitly optimizes the performance of T1 mapping for a wide range of T1 values.  The method yielded 3 flip angle designs with performance similar to the previously described 10 flip angle design.  This development may allow more efficient T1 mapping optimized for wide range of tissue types.

13:30         3082.     Standardized Structural Magnetic Resonance Imaging in Multi-Centre Studies Using Quantitative T1 and T2 Imaging

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Sean CL Deoni¹, Steven CR Williams², Peter Jezzard¹, John Suckling³, Declan GM Murphy², Derek K. Jones⁴

¹University of Oxford, Oxford, UK; ²Institute of Psychiatry, London, UK; ³University of Cambridge, Cambridge, UK; ⁴Cardiff University Brain Research Imaging Centre, Cardiff, UK

Multicentre studies are becoming increasingly common as they facilitate the recruitment of greater numbers of subjects while decreasing the economic cost and duration of study.  However, precise matching of structural image quality, necessary to draw meaningful inferences from the data particularly in regards to morphology, becomes difficult as the number and diversity of imaging systems increases.  Here we report on the use of quantitative T1 and T2 imaging for standardizing the structural imaging component of such studies, demonstrating high reproducibility of the measures across different systems.

14:00         3083.     Combining Morphometry and T1 Relaxometry in a Single Imaging Protocol: Measuring T1 with MPRAGE

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Olivier Mougin¹, Penny Gowland¹

¹School of Physics and Astronomy, Nottingham, UK

We are using relaxation times to study normal and pathological brain development. Acquisition times for T1 are generally long, so this study aims to make use of the anatomical image that is acquired for morphological information into the relaxometry protocol. Therefore we have optimized the Magnetization Preparation followed by a RApid Gradient Echo (MPRAGE) sequence (which is routinely used for morphology at our site) for the measurement of T1. Study on five subjects at three different fields shows agreement with the literature and gold standard sequences.

14:30         3084.     Fast T1 Mapping in Human Brain Using Inversion Recovery EPI with GRAPPA at 3T and 7T

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John Grinstead¹, William Rooney²

¹Siemens Medical Solutions USA, Inc., Portland, USA; ²Oregon Health & Science University, Portland, USA

Quantitative T1 techniques find a wide range of applications in biological NMR, but the major drawback of these techniques is that they are slow. This is because the sampling requirements are high, not only must the T1 recovery be well sampled, but also spatial encoding is usually desired. This work investigates the combination of inversion recovery echo-planar and parallel imaging techniques for high-speed acquisition of quantitative T1 data sets in human brain at 3T and 7T.

15:00         3085.     Measurement of R1 Dynamics Using a 3D FLASH Variable Flip Angle Sliding Window Technique

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Jessica Schulz¹,², Eva Christina Wönne¹, Arne Hengerer², Wolfhard Semmler¹, Michael Bock¹

¹Deutsches Krebsforschungszentrum (dkfz), Heidelberg, Germany; ²Siemens Medical Solutions, Erlangen, Germany

A 3D FLASH variable flip angle method was combined with a sliding window calculation to obtain the relaxation rates R1 dynamically with a temporal resolution of 10 s. In a contrast agent study on tumor-bearing mice the contrast agent-related changes in R1 could be mapped in tumors, and the R1 values were in excellent agreement with reference measurements.

Shared Resources & Quality Control

13:30         3086.     The Neuroimaging Informatics Tools and Resources Clearinghouse (NITRC)

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David N. Kennedy¹, Robert Buccigrossi², Jeff Grethe, Christian Haselgrove, Nina Preuss, Keith Wagner, Mark Ellisman

¹MGH, Charlestown, Massachusetts, USA; ²Turner Consulting Group, USA

NITRC, a new neuroimaging knowledge environment, is now online (www.nitrc.org). We encourage the fMRI community to try it out and provide feedback on its design, tools, resources, and content. NITRC is a knowledge environment for the fMRI community where tools and resources are presented in a coherent and synergistic environment for the advancement of MRI-based neuroscience research.

14:00         3087.     PAQAP: A Quality Assessment Protocol for MRI

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Pieter Vandemaele¹, Rik Achten¹, Yves De Deene¹

¹Ghent University Hospital, Ghent, Belgium

Quality assessment in MR imaging provides clinician and researchers with objective measures of the performance of their MR scanner and scan protocols. PAQAP (Pieter’s Automated Quality Assurance Protocol) is a combination of a standard QA phantom and an elaborate software program for full automatic data analysis and report generation. PAQAP provides an easy way to acquire and process QA data on a regular basis with minimal interaction and within a limited time frame by an MR technologist. The system will be implemented and systematically used in a QA program at the experimental MR site of the Ghent University Hospital.

14:30         3088.     MR Image Quality Evaluation Using Weighted Perceptual Difference Model (Case-PDM)

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Jun Miao¹, Wilbur C. K. Wong¹, David L. Wilson¹,²

¹Case Western Reserve University, Cleveland, USA; ²University Hospital of Cleveland, Cleveland, USA

The perceptual difference model (Case-PDM) is being used to quantify image quality of fast, parallel MR acquisitions and reconstruction algorithms by comparing to slower, full k-space, high quality reference images. In this paper, we create an alternative metric weighted to image features to improve the linear correlation coefficient between human ratings and weighted Case-PDM, across a large set of MR reconstruction test images of varying quality. Our method is robust across subjects and anatomy; that is, scores maintain a high correlation with human ratings even if the test dataset is different from the training dataset.

15:00         3089.     A Novel SNR Estimation Technique Applicable to Clinical Parallel MR Images: Triple Band-Width Single Acquisition Method (TriSAM)
[Not Available]

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Yoshio Machida¹, Hiroshi Kusahara¹, Yoshimori Kassai¹

¹Toshiba Medical Systems Corporation, Otawara, Japan

We have developed a new technique �gTriple band-width Single Acquisition Method�h (TriSAM) in which noise maps can be obtained with originally intended target images with no extra scan time. Application of this technique with parallel imaging to the head images on a volunteer provides the misregistration free noise images. The TriSAM is considered to be one of the most practical SNR estimation approaches for clinical images.

B₁Mapping

13:30         3090.     Optimal Spoiling of the Transverse Magnetization in the Actual Flip-Angle Imaging (AFI) Sequence for Fast B₁ Field Mapping

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Vasily L. Yarnykh¹

¹University of Washington, Seattle, Washington, USA

A recently developed Actual Flip-angle Imaging (AFI) method allows fast B1 mapping based on the spoiled steady-state principle. This study presents theoretical and experimental examination of conditions required for optimal spoiling in the AFI sequence. It was found that the spoiling behavior of the AFI sequence is different from a traditional spoiled gradient echo sequence. To achieve optimal spoiling, appropriate combinations of an RF phase increment and spoiler gradient areas need to be used. The sequence design providing highly accurate B1 measurements and possible sources of errors are described.

14:00         3091.     In-Vivo Assessment of a STEAM Sequence for B1-Mapping

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Rudolf Stollberger¹, Thomas Birngruber²

¹Graz University of Technology, Graz, Austria; ²Medical University of Graz, Austria

RF field inhomogeneities are a main source for image inhomogeneities, spatial dependent SNR and CNR and systematic errors in quantification of MRI data. A STEAM sequences was evaluated in-vivo at 3T for B1-determination in quantitative studies. It could be shown that the sequence is robust and sufficiently accurate for the application in most regions. Some problems occur in the chest from motion artefacts. The acquisition time for a scanning matrix of 128*64 was 47s for TR=800ms and 78s for TR=1300.

14:30         3092.     Impact of the Correction of B1 Inhomogeneities for Dynamic Contrast-Enhanced Imaging at 3 Tesla

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Robert Merwa¹, Franz Ebner², Rudolf Stollberger¹

¹Graz University of Technology, Graz, Austria; ²Medical University of Graz, Graz, Austria

This study was performed in order to evaluate the influence of the B1-inhomogenities for dynamic contrast-enhanced MRI at 3 T. The active RF-field was measured with a stimulated echo sequence whereas the actual flip angle distribution is determined. Using a reference scan and a perfusion scan particular parameters as temporal T1 relaxation time, concentrations and arterial input function can be calculated. The results obtained with the correction of the flip angles show a significant improvement compared to the results obtained without correction. All the measurements were performed on a 3 T System (Siemens Magnetom Trio a Tim System)

15:00         3093.     Rapid RF Flip Angle Imaging

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Daniel Kim¹, Sohae Chung¹, Daniel K. Sodickson¹, Leon Axel¹

¹New York University, New York, New York, USA

The transmit radiofrequency (RF) filed (B1) uniformity plays an important role in determining the image quality in MRI, particularly at high field strengths (&[ge] 3T). Accurate B1 or flip angle maps are needed to compensate for B1 variations through different compensation strategies. Among the existing methods for in vivo B1 mapping, the double angle method (DAM) is most straightforward. However, its image acquisition efficiency is very low due to a need to set TR &[ge] 5 T1s. The purpose of this study is to develop a rapid in vivo B1 mapping method based upon three single-shot image acquisitions.

Image Registration & Alignment

13:30         3094.     Validation of 3D Non-Rigid Whole Body MR Image Registration

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Xia Li¹, Thomas Yankeelov, Todd Peterson, John Gore, Benoit Dawant

¹Vanderbilt University, Nashville, Tennessee, USA

The automatic registration of whole body MR images, which requires non-rigid registration techniques for the

articulated structures, remains a challenge. Although we proposed a promising registration method that permits the automatic registration of MR images for both intra- and inter-subject, one weakness is found in this algorithm: bones can be deformed incorrectly because of the surrounding structures. A modified method was proposed to constrain the deformation of bony structures. However, complete validation is required. In this study, quantitative validation results show the accuracy of our algorithm.

14:00         3095.     Breast MR Registration for Evaluation of Neoadjuvant Chemotherapy Response

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Ruparani Chittineni¹,², Min-Ying Su¹, Orhan Nalcioglu¹

¹University of California, Irvine, Irvine, USA

The deformable nature of breast tissue results in significant shape differences between serial studies, making it challenging to chalk out a clear trajectory of the corresponding tumor locations. These studies correspond to MR-based monitoring of chemotherapy for therapy response evaluation. In this abstract we demonstrate the use of constraint based free-form deformations for registration of serial breast MR studies. The algorithm is especially useful in patients with multi-centric or multi-focal lesions. Also, differentiating between therapy-induced inflammation and residual disease becomes amenable. Since, tumor volumes are preserved during the transformation, mis-interpretation of results can be avoided.

14:30         3096.     Image Registration of Mouse Brains Containing Varying Amounts of Extra Cortical CSF

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Matthijs C. van Eede¹, Jason P. Lerch¹, John G. Sled¹

¹Toronto Centre for Phenogenomics, Toronto, Canada

In recent studies we encountered brains containing varying amounts of extra cortical CSF. Using our groupwise registration method for analysis of the brains, we found this resulted in incorrect alignment. That would lead to incorrect findings. We have developed a modulation strategy to deal with this extra cortical CSF, alleviating the registration problem.

15:00         3097.     Non-Rigid Registration of Diffusion Weighted MRI Using Progressive Principal Component Registration (PPCR)

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Andrew Melbourne¹, David Hawkes¹, David Atkinson¹

¹University College London, London, UK

Artefacts as a result of patient motion & eddy current distortions often corrupt Diffusion Weighted MR images, reducing the success of subsequent analysis. Registration of images that contain different contrast from each gradient direction may produce inaccurate results. The PPCR scheme allows diffusion direction images to be registered into a common coordinate frame by combining overlapping diffusion contrast using principal components analysis. PPCR registration is compared to data registered using an affine registration of each diffusion direction to the corresponding B0 volume. The use of the PPCR method allows enhanced feature demarcation by removing geometric distortion artefacts.

13:30         3098.     Restoration of Compressed or Constricted Images: A Feasibility Study for Intra- And Inter- Imaging Modality Registration

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Ruparani Chittineni¹, SeungHoon Ha¹, Werner Roeck¹, Min-Ying Su¹, Orhan Nalcioglu¹

¹University of California, Irvine, Irvine, USA

Restoring form of compressed or deformed images is of utmost significance. Automatic non-rigid registration techniques have been applied extensively to address non-linear deformations. However, it is interesting to note that such algorithms may fail or be biased towards dominant intensity regions in the images and hence have minimal local registration. We demonstrate and compare the applicability of automatic and landmark based methods for the particular case of addressing deformation in the presence of constriction or applied compression. The near future application of the developed method is for co-registration of breast images acquired using MRI (uncompressed) and scintimammography (under light compression).

14:00         3099.     Registration of 3D MR Images of the Mouse Embryos

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Mojdeh Zamyadi¹,², R Mark Henkelman¹,², Shoumo Bhattacharya³, Jurgen E. Schneider³, John G. Sled¹,²

¹University of Toronto, Toronto, Canada; ²Mouse Imaging Centre, Hospital for Sick Children, Toronto, Canada; ³University of Oxford, Wellcome Trust Centre for Human Genetic, Oxford, UK

We are developing an image registration technique to detect subtle anatomical shape differences between 3D MR images of mouse embryos. In order to assess feasibility, we have used non-linear registration to align a group of genetically identical embryos. We tested the assumption that embryo anatomy is highly conserved among specimens by registering six 3D embryos together. The result of the registration process is shown in form of a final average image consisting of data from the 6 individuals, and the root mean squared (RMS) displacement image which is a representation of the

anatomical variation among the genetically identical embryos. These initial findings suggest that embryo anatomy is highly conserved among specimens and that image registration of 3D MRI data is a feasible approach for subsequently detecting abnormal phenotypes.

14:30         3100.     Quality Control in a Longitudinal Multi Center Alzheimer's Disease Study

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Eric Westman¹, Andy Simmons², Sebastian Muehlboeck³, Tony Segerdahl⁴, Johan Bengtsson⁴, Lars-Olof Wahlund¹, Simon Lovestone², Christian Spenger⁴

¹Department of Neurobiology, Health Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden; ²MRC Centre forNeurodegeneration Research, Institute of Psychiatry King's College, London, UK; ³McConnell Brain Imagi

Within the InnoMed/AddNeuroMed research project funded by the European Union, sixth frame work program, data has been successfully collected for a multi site MRI study. Quality control and quality assurance are performed on routine basis at data collection centers and at the data coordination centre. The feature-set of the database system covers the entire process from image acquisition, storage, quality control to data querying for analysis. Quality control statistics show that the performance of the participating sites is very high; 97 % of all T1 images passed QC.  

15:00         3101.     Validation of User Independent Planning Tool for Consistent Data Acquisition in Multi-Center Trials

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Esben Thade Petersen¹,², Ivan Zimine¹,³, Xavier Golay,¹⁴, The QUASAR Reproducibility study

¹National Neuroscience Institute, Singapore, Singapore; ²Aarhus University Hospital, Aarhus, Denmark; ³Philips Medical Systems, Tokyo, Japan; ⁴Singapore Bioimaging Consortium, Singapore, Singapore

In this work, we evaluated the accuracy of automatic slice positioning which recently has become available on standard MRI systems. The success of MRI studies often depends on the consistency of the image acquisition and is especially important in longitudinal and multi-center trials. Differences in slice angulations and positioning can easily affect the “subjective” reading by radiologists but also the quantification in DTI, perfusion or volumetric-imaging. Three automatically planned images were acquired in 170 subjects and minor rotation and translation between scans were observed after co-registration of the images, resulting in high consistency for future trials using these tools.

13:30         3102.     Exploring the Relationship Between Natural Fluctuations in Electrical Measures of Brain Activity and the BOLD Response, During Visual Stimulation

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Karen J. Mullinger¹, Gerda B. Geirsdottir¹, Matthew J. Brookes¹, Peter F. Liddle¹, Richard W. Bowtell¹

¹University of Nottingham, Nottingham, UK

The correlation of preceding alpha power and driven power with the BOLD response to a visual stimulus has been investigated using simultaneous EEG/fMRI experiments at 3 T. Despite good characterisation of the BOLD and electrical responses no correlation was found between the fluctuations in the alpha power preceding the stimulus or in the driven power and the BOLD response in data from individual subjects. A positive trend was however found when comparing the fractional difference in BOLD response and preceding alpha power in trials falling in the top and bottom quartiles binned according to the preceding alpha power across subjects.

14:00         3103.     Hemispherical Constrained Surface Controller for 3D Navigation

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Martin John Graves¹, David John Lomas¹

¹University of Cambridge and Addenbrooke's Hospital, Cambridge, UK

Although there has been significant development of volumetric image acquisition methodologies there has been little development of methods for subsequent reformatting of data beyond standard linear tools. This work describes the development of a 3D constrained surface controller for interrogating volumetric data. The controller allows for intuitive navigation by following an ultrasound-style motion paradigm in which data reformatting is performed over a virtual hemispherical surface around the organ of interest. Constraining the motion to an anatomically consistent surface reduces the possibility of the operator becoming spatially disorientated. The controller was evaluated in comparison to conventional reformatting software.

14:30         3104.     Uncertainty in Simultaneous Estimation of Blood Oxygenation Level and Volume Fraction on the Basis of Spin Dephasing in a Vascular Network

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Jan Sedlacik¹,², Jürgen R. Reichenbach¹

¹University Clinics of the Friedrich Schiller University, Jena, Germany

Blood oxygenation level and volume fraction are essential input parameters of theoretic models of spin dephasing in a vascular network. It is possible to estimate these parameters by fitting the simulated signal to measured signal-time curves. However, if the blood oxygenation level and volume fraction are unknown, they can not be reliably estimated by simply fitting theoretical signal curves to the measured signal decay. The purpose of this work was to unravel this difficulty of a simultaneous estimation of blood oxygenation level and volume fraction.

15:00         3105.     Local Feature-Preserving Sele