Tobias Hahn¹, Andreas Steingoetter^1,2, Werner Schwizer², Martin Buehrer¹, Sebastian Kozerke¹, and Peter Boesiger^1
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.

Jiang Du¹, Eric Diaz¹, Richard Znamirowski¹, Sheronda Statum¹, Darryl DLima², Graeme Bydder¹, and Christine Chung^1
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.

Holger Eggers¹, Thomas G Perkins², and Shahid M Hussain^3,4
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.

Elsayed H Ibrahim¹, Wolfgang Rehwald², Bradley Sutton³, Sven Zuehlsdorff², and Richard D White^1
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.

Alex Frydrychowicz¹, Eric Niespodzany², Scott B Reeder¹, Kevin M Johnson³, Oliver Wieben², and Christopher J François^1
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.

Jian Xu^1,2, Daniel Kim¹, Ricardo Otazo¹, Monvadi Srichai¹, Ruth Lim¹, Kellyanne Mcgorty¹, Ryan Avery¹, Leon Axel¹, Thoralf Niendorf³, and Daniel Sodickson^1
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.

Manojkumar Saranathan¹, Mohammad Mehdi Khalighi², Adam B Kerr³, and Brian Rutt^1
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.

Mohammad Mehdi Khalighi¹, Gary H. Glover², Prachi Pandit², Scott Hinks³, Adam B. Kerr⁴, Manojkumar Saranathan², and Brian K. Rutt^2
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.

Weili Zheng¹, E Mark Haacke¹, Saifeng Liu², Jaladhar Neelavalli³, and Helen Nichol^4
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.

Weili Zheng¹, E Mark Haacke¹, and Helen Nichol^2
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.