Emerging Body MR Techniques
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Monday 7 May 2012
Room 219-220  14:15 - 16:15 Moderators: Brian A. Hargreaves, Claude B. Sirlin

14:15 0102.   Multi-Peak Spectral Modeling of Fat is Necessary for both Accurate Liver Fat and Iron Quantification: a Biopsy-MRI Correlation Study
Jens-Peter Khn1,2, Diego Hernando1, Norbert Hosten2, and Scott B Reeder1,3
1Department of Diagnostic Radiology, Wisconsin Institutes for Medical Research USA, Madison, Wisconsin, United States, 2Department of Diagnostic Radiology, University Greifswald, Greifswald, MV, Germany, 3Medical Physics, Biomedical Engineering and Medicine, Wisconsin Institutes for Medical Research USA, Madison, Wisconsin, United States

Chemical shift-encoded MRI methods provide measures of liver fat, and also R2*, a biomarker for hepatic iron content. Previous works have shown that correcting for the spectral complexity of fat (multi-peak modeling) is necessary for accurate fat quantification, however it is unknown whether it is necessary for accurate iron quantification. In this work, we investigated the impact of multi-peak fat modeling on R2* measurements to assess hepatic iron content, using biopsy as reference standard. In the presence of fat, single-peak fat modeling results in clinically significant errors in R2* quantification. Multi-peak fat modeling removes these errors and is necessary for accurate hepatic iron quantification.

14:27 0103.   Tagged MRI of the Liver in the Diagnosis of Liver Cirrhosis, preliminary study.
Lorenzo Mannelli1, Christopher A Potter1, Theodore J Dubinsky1, Orpheus Kolokythas1, Manjiri K Dighe1, and Jeffrey H Maki1
1University of Washington, Seattle, WA, United States

The tag-MRI technique is routinely used to quantify myocardial muscle contractility by measuring myocardial strain after application of tags. Tissue strain and stiffness are inversely proportional in that the stiffer a tissue is, the less deformable it becomes. The principal strain represents the amount of the greatest elongation or stretch of the tissue at a given location. Since the liver becomes increasingly stiffer as chronic liver disease progresses, increments in liver stiffness should be reflected by changes in liver strain, which can be quantified using tag-MRI.

14:39 0104.   Optimized Caipirinha acceleration patterns for routine clinical 3D imaging
Vibhas Deshpande1, Dominik Nickel2, Randall Kroeker3, Stephan Kannengiesser2, and Gerhard Laub1
1Siemens Healthcare, San Francisco, CA, United States, 2Siemens Healthcare, Erlangen, Germany, 3Siemens Healthcare, Winnipeg, Canada

Shortening scan time in abdominal breath-hold VIBE imaging is important for patient comfort and consistent diagnostic results in sick or uncooperative patients. In this work, a recently proposed parallel imaging method, Caipirinha, was evaluated against standard GRAPPA to find an optimal sampling pattern. Caipirinha reduces g-factor related SNR losses and controls aliasing such that higher accelerations can be used with little compromises in image quality. Caipirinha showed very good results with accelerations 3 and 4, and improvements over GRAPPA. For a typical abdominal exam setup, a 131 pattern (total acceleration=3) pattern was found to be most consistent across all subjects.

14:51 0105.   Clinical Performance and Validation of a Compressed Sensing Contrast Enhanced MRI with Fast Image Reconstruction
Shilpy Chowdhury1, Tao Zhang2, Richard A Barth1, Michael Lustig3, Mark Murphy3, Marcus T Alley1, Thomas Grafendorfer4, Paul Calderon5, John M Pauly2, Brian A Hargreaves1, and Shreyas S Vasanawala1
1Radiology, Stanford University, Stanford, California, United States, 2Electrical Engineering, Stanford University, Stanford, California, United States, 3Electrical Engineering and Computer Sciences, University of California Berkeley, Berkeley, California, United States, 4ATD Coils, GE Healthcare, Stanford, California, United States, 5MR Hardware Engineering,GE Healthcare, Fremont, California, United States

Pediatric abdominal MRI is challenged by small anatomical structures and physiologic motion. We assessed performance and clinical validation of a new compressed sensing algorithm in 29 consecutive patients, that permits rapid reconstruction even with high-density coils. A 3D SPGR sequence with intermittent fat suppression and Poisson-disc variable density k-space sampling was developed. 3 reconstructions included parallel imaging (ARC), compression sensing (L1-SPIRiT) and coil compressed (CC) L1-SPIRiT. CC-L1-SPIRiT showed better image quality performance for most qualitative assessments. Compressed sensing with fast image reconstruction is feasible in a pediatric clinical environment and can improve quality of structural delineation in pediatric MRI.

15:03 0106.   
Characterization of Small Liver Lesions using Partial Volume Corrected T2 Estimates Obtained from Highly Undersampled Radial Fast Spin Echo Data via PURIFY
Chuan Huang1, Jean-Philipper Galons2, and Maria I Altbach2
1Mathematics, University of Arizona, Tucson, Arizona, United States, 2Radiology, University of Arizona

T2 estimation has proven to be a valuable tool in the characterization of liver lesions. Because of the partial volume effect, it is particularly challenging to obtain T2 values of lesions with diameters smaller than 15 mm. In this work we present a joint bi-exponential fitting (JBF) algorithm combined with a principal component based reconstruction algorithm to obtain accurate T2 estimates with partial volume correction. The method, which utilizes highly undersampled radial data acquired in a single breath hold, is demonstrated in phantoms and in vivo.

15:15 0107.   Combined Dual Frequency 19F and 1H MRI in the human digestive tract
Tobias Hahn1, Ruben Pellicer Guridi1,2, Werner Schwizer3, Sebastian Kozerke1, Michael Fried3, Peter Boesiger1, and Andreas Steingoetter1,3
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, 2Department of Biophysics and Bioengineering, University of Barcelona, Barcelona, Spain, 3Dep. of Internal Medicine, Division of Gastroenterology and Hepatology, Zurich, Switzerland

This study presents the 3D tracking of fluorine labeled capsules through the human intestinal tract using a dual frequency excitation scheme with a temporal resolution of 255ms. Liquid fluorine markers were Hexafluorobenzene and Perfluoro-15-crown-5-ether and capsule filling was 65l each. The study was performed in five healthy volunteers on two study days. Initial results are shown regarding the temporal and structural behavior of the capsule passages through the digestive tract.

15:27 0108.   Overcoming the low relaxivity of gadofosveset at high field with spin locking
Owen C Richardson1, Marietta Scott2, Steven F Tanner1, John C Waterton2, and David L Buckley1
1Division of Medical Physics, University of Leeds, Leeds, West Yorkshire, United Kingdom, 2Imaging, Personalised Healthcare and Biomarkers, AstraZeneca, Macclesfield, Cheshire, United Kingdom

Gadofosveset binds reversibly to serum albumin (SA), and has a high longitudinal relaxivity at lower magnetic fields ( 3.0 T) but a much lower relaxivity at high fields. Spin locking (SL) is sensitive to macromolecular content; it is hypothesised that combining SL with albumin binding may enable increased gadofosveset relaxivity at high fields. In vitro measurements at 4.7 T found significantly higher SL relaxation rates, R1 (1/T1), when gadofosveset was SA-bound than when unbound. R1 values for a non-binding contrast agent (gadopentetate) in SA were similar to unbound gadofosveset. SL at high field generates significantly higher relaxation rates for gadofosveset than conventional agents, and may enable differentiation of free and bound molecules at these field strengths.

15:39 0109.   Noninvasive investigation of iron elimination from the liver following ferumoxytol administration
Pippa Storey1, Hersh Chandarana1, Andrew B. Rosenkrantz1, David R. Stoffel1, Ruth P. Lim1, and Vivian S. Lee1,2
1Radiology Department, New York University School of Medicine, New York, NY, United States, 2University of Utah, Salt Lake City, UT, United States

The recent approval of Feraheme (ferumoxytol) for human use in the USA has increased interest in the use of ultrasmall superparamagnetic iron oxide (USPIO) particles as MRI contrast agents. USPIO particles have a wide range of potential applications, both overlapping with and complementary to those of gadolinium. However, an important consideration is their elimination time. We used T2* mapping to investigate the elimination of iron from the liver following administration of ferumoxytol (5mg/kg Fe) in six healthy volunteers. Elimination times varied widely among subjects, from less than 3 months in one person to longer than 11 months in three people.

15:51 0110.   
Combined IVIM and DTI for simultaneous assessment of diffusion and flow anisotropy of the kidney
Mike Notohamiprodjo1,2, Hersh Chandarana3, Artem Mikheev2, Jose Garcia Raya2, John Grinstead4, Thorsten Feiweier4, Henry Rusinek3, Vivian S Lee3,5, and Eric E Sigmund2
1Department of Clinical Radiology, University Hospitals Munich, Munich, Bavaria, Germany, 2Center for Biomedical Imaging, NYU Langone Medical Center, New York City, NY, United States, 3Department of Radiology, NYU Langone Medical Center, 4Siemens Healthcare, 5University of Utah Health Care

We used a combined IVIM-DTI methodology to resolve the ambiguity of renal diffusion anisotropy by distinguishing structural from flow effects. We observe a significantly higher perfusion-fraction (fp) of the cortex than medulla, contrary to previous studies finding comparable fp in both tissues. Higher medullary FA at the low b-value range and high directional variance of medullary fp suggest anisotropy of the perfusion-fraction. Similarly, both flow and diffusion appear to contribute to the diffusion anisotropy of the renal medulla. This novel method may be useful in separating decreased tubular flow from irreversible structural tubular damage, e.g. in diabetic nephropathy.

16:03 0111.   Ultra-Fast Steady State Free Precession and its Application to In Vivo 1H Lung Imaging
Oliver Bieri1
1Division of Radiological Physics, Department of Radiology and Nuclear Medicine, University of Basel Hospital, Basel, Switzerland

Ultra-fast steady state free precession (SSFP) imaging refers to Cartesian SSFP imaging protocols using repetition times close to 1ms, as can be achieved with clinical whole body systems by fully exploiting and optimizing gradient switching patterns and RF pulse settings in combination with asymmetric echo readouts. Typically, an isotropic resolution of ~1.8mm can be achieved with repetition times TR ~ 1.4ms (TE ~ 0.5ms), providing high-resolution 3D artifact free balanced SSFP images even for targets with severe susceptibility variations, such as the lung.