Applications & Evaluations of State-of-the-Art Sequences
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Thursday May 12th
Room 710A  10:30 - 12:30 Moderators: Priti Balchandani and Jean Brittain

10:30 571.   Simultaneous 3D tracking of multiple 19F labeled capsules using a 3D Golden Angle sampling scheme 
Tobias Hahn1, Andreas Steingoetter1,2, Werner Schwizer2, Martin Buehrer1, Sebastian Kozerke1, and Peter Boesiger1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, 2Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland

Tracking of single fluorine labeled markers or capsules has previously been performed for gastrointestinal and catheter tracking applications using three orthogonal projections. For these applications, simultaneous fast tracking of multiple capsules is highly desirable. However, for multiple capsule tracking three orthogonal projections are not sufficient anymore for unambiguous capsule position detection. Therefore, in this work the use of a radial sampling scheme with 3D Golden Angle projections for simultaneous multiple capsule tracking is studied. Simultaneous tracking of four capsules with velocities < 13.5 mm/s using different reconstruction window sizes is found feasible with good tracking reliability.

10:42 572.   Ultrashort TE Spectroscopic Imaging (UTESI): an Efficient Technique for Free and Bound Water Quantification 
Jiang Du1, Eric Diaz1, Richard Znamirowski1, Sheronda Statum1, Darryl DLima2, Graeme Bydder1, and Christine Chung1
1Radiology, University of California, San Diego, San Diego, California, United States, 2Scripps Reseach Institution

It is well accepted that biological tissues commonly contain distinct water compartments and display two or more T2 components. However, conventional T2 relaxometry still focuses on single component analysis using multi-echo spin echo sequences, which typically cannot detect signal from the short T2 components in a variety of musculoskeletal (MSK) tissues. Here we propose a bi-component T2* analysis of images from ultrashort TE spectroscopic imaging (UTESI) sequence to quantify T2* and fractions of the free and bound water components in a series of MSK tissues.

10:54 573.   Influence of Spectral Model and Signal Decay on Hepatic Fat Fraction Measurements at 3 T with Dual-Echo Dixon Imaging 
Holger Eggers1, Thomas G Perkins2, and Shahid M Hussain3,4
1Philips Research, Hamburg, Germany, 2Philips Healthcare, Cleveland, OH, United States, 3University of Nebraska Medical Center, Omaha, NE, United States, 4The Nebraska Medical Center, Omaha, NE, United States

The accurate estimation of fat fractions in the liver with MRI is complicated by various effects, including signal modulation due to the spectral composition of fat and signal decay due to transverse relaxation. These effects have been addressed in multi-echo imaging by more complex signal models, exploiting the availability of more data for a robust fit. In this work, corrections applicable in dual-echo imaging are explored, with which similar quantitative results as with six-echo imaging may be obtained. Thus, fat fractions may be derived from routine clinical scans with higher spatial resolution and larger coverage in single breath-holds.

11:06 574.   Comparison of different data acquisition strategies in myocardial strain assessment using strain-encoded (SENC) MRI 
Elsayed H Ibrahim1, Wolfgang Rehwald2, Bradley Sutton3, Sven Zuehlsdorff2, and Richard D White1
1Department of Radiology, University of Florida, Jacksonville, FL, United States, 2Siemens Medical Solutions, Cardiovascular MRI R&D, Chicago, IL, United States,3Department of Bioengineering, University of Illinois, Urbana-Champaign, IL, United States

Strain-encoding (SENC) MRI was recently introduced for measuring myocardial strain with high resolution and simple post-processing. In a typical scan, data is acquired line-by-line in a rectilinear fashion with long scan-time. In this work, radial and spiral acquisitions were implemented in SENC for improved image-quality. The developed sequences were tested on volunteers and results were evaluated and compared to standard Cartesian acquisition. The measurements from the three techniques showed good agreement by Bland-Altman analysis. Radial and Cartesian images showed similar image-quality. While partial radial acquisition could not achieve high spatial-resolution, spiral acquisition allowed for both high spatial-resolution and short scan-time.

11:18 575.   Validation of 4D velocity mapping using 5-point PC-VIPR for blood flow quantification in the thoracic aorta and main pulmonary artery. 
Alex Frydrychowicz1, Eric Niespodzany2, Scott B Reeder1, Kevin M Johnson3, Oliver Wieben2, and Christopher J François1
1Department of Radiology, University of Wisconsin - Madison, Madison, WI, United States, 2Departments of Radiology, Medical Physics, University of Wisconsin - Madison, Madison, WI, United States, 3Department of Medical Physics, University of Wisconsin - Madison, Madison, WI, United States

4D velocity mapping is increasingly used for hemodynamic analyses. PC-VIPR is a time-efficient acquisition strategy applying radial undersampling for imaging with high spatial resolution and large volume coverage. The employed 5-point velocity encoding increases the velocity sensitivity spectrum while preserving high VNR at a small scan time penalty, thus enabling simultaneous morphologic and hemodynamic evaluation of large vascular territories. We validated 5-point PC-VIPR for aortic and pulmonary flow measurements in healthy volunteers. Phantom-corrected 2D phase contrast acquisitions and cardiac CINE bSSFP volumetry served as reference standards. Results show good agreement underlining the clinical applicability of 5-point PC-VIPR for flow quantification.

11:30 576.   Initial Comparative Evaluation of a Five-Minute Comprehensive Cardiac MR Examination Using Highly Accelerated Parallel Imaging 
Jian Xu1,2, Daniel Kim1, Ricardo Otazo1, Monvadi Srichai1, Ruth Lim1, Kellyanne Mcgorty1, Ryan Avery1, Leon Axel1, Thoralf Niendorf3, and Daniel Sodickson1
1Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States, 2PolyTechnic Institute of NYU and Siemens Medical Solutions USA Inc., New York, NY, United States, 3Charite' - University Medicine, Berlin-Buch, Germany

The feasibility of a 5-minute comprehensive whole heart protocol using highly accelerated parallel imaging was recently reported. In the current study, we have incorporated this 5-minute comprehensive protocol into routine clinical CMR examinations and have performed initial comparisons between a standard (predominantly 2D) protocol and the new 5-minute 3D comprehensive protocol arranged to occur within a single common scan session.

11:42 577.   Fast 3D B1+ mapping using an optimized, asymmetric Bloch-Siegert method 
Manojkumar Saranathan1, Mohammad Mehdi Khalighi2, Adam B Kerr3, and Brian Rutt1
1Radiology, Stanford University, Stanford, CA, United States, 2Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States, 3Electrical Engineering, Stanford University, Stanford, CA, United States

B1+ mapping is important in a number of high-field imaging applications including multi-transmit rf pulse design and MR relaxometry. The recently proposed Bloch-Siegert (BS) B1+ mapping method circumvents spoiling and saturation issues faced by magnitude-based methods such as Actual Flip-angle Imaging (AFI) and the Double Angle Method. While the BS method is relatively fast due to its T1 insensitivity, its accuracy depends on the power of the BS pulse, which is SAR limiting, especially at 7T. This SAR limit can prolong acquisition times, especially for multiple transmit channel B1+ mapping applications. We propose a novel, fast whole brain 3D Bloch-Siegert B1+ mapping method that is optimized for very short scan times and low SAR and demonstrate isotropically resolved whole human brain B1+ mapping in scan times on the order of 30 seconds at 3T and a minute at 7T.

11:54 578.   Single-Shot Spiral Based Bloch-Siegert B1+ Mapping 
Mohammad Mehdi Khalighi1, Gary H. Glover2, Prachi Pandit2, Scott Hinks3, Adam B. Kerr4, Manojkumar Saranathan2, and Brian K. Rutt2
1Global Applied Science Laboratory, GE Healthcare, Menlo Park, California, United States, 2Department of Radiology, Stanford University, Stanford, California, United States, 3Global Applied Science Laboratory, GE Healthcare, Waukesha, Wisconsin, United States, 4Department of Electrical Engineering, Stanford University, Stanford, California, United States

Fast and accurate B1+ mapping is needed in high field MRI for different applications like parallel transmit or quantitative relaxometry. Bloch-Siegert (BS) B1+ mapping is an accurate method; however it suffers from high RF deposition (SAR) at high field and consequently long scan times. To overcome this limitation, we have integrated the BS method into a single-shot spiral sequence at 7T, and have shown that it reduces SAR and scantime significantly, with similar angle-to-noise ratio, compared to a gradient echo based BS method. Whole-brain B1+ maps can be obtained at 7T in less than 10 seconds using the new method.

12:06 579.   Quantification of Susceptibility Mapping with Synchrotron X-ray Fluorescence Iron Mapping 
Weili Zheng1, E Mark Haacke1, Saifeng Liu2, Jaladhar Neelavalli3, and Helen Nichol4
1Radiology, Wayne State University, Detroit, Michigan, United States, 2School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada, 3The Magnetic Resonance Imaging Institute for Biomedical Research, Detroit, Michigan, United States, 4Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada

Susceptibility weighted imaging (SWI) has been widely accepted as an in vivo neuroimaging technique for monitoring neurologic disorders with iron-related susceptibility changes. We assumed that ferritin was the dominant iron species in putamen and caudate and estimated the relationship between SWIM susceptibility and iron concentration, for the first time on a voxel by voxel basis. This provides a major advance in noninvasive and safe estimation of iron in human brain tissue in vivo using susceptibility mapping.

12:18 580.   Correlation between Elemental Distribution and Susceptibility Change in Intracerebral Hemorrhagic Stroke 
Weili Zheng1, E Mark Haacke1, and Helen Nichol2
1Radiology, Wayne State University, Detroit, Michigan, United States, 2Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada

Both T2* weighted imaging (T2*WI) and susceptibility weighted imaging (SWI) are sensitive to local susceptibility change and widely used in similar clinical applications. Here, we introduced synchrotron Rapid Scanning X-ray Fluorescence (RS-XRF) to investigate how major elements are related to the susceptibility change in intracerebral hemorrhagic stroke (ICH) and how T2*WI and SWI represent it. We find SWIM is superior to T2* for imaging iron in hemorrhage and can differentiate Ca from Fe. SWIM and T2* map complement each other and can provide more specific and accurate spatial and chemical information in ICH and other Fe/Ca related susceptibility changes.