ISMRM 24th Annual Meeting & Exhibition • 07-13 May 2016 • Singapore

Scientific Session: Fat/Water Imaging

Wednesday, May 11, 2016
Room 324-326
10:00 - 12:00
Moderators: Dimitrios Karampinos, Brian Welch

Resolving Uncertainties of IDEAL Fat-Water Imaging Using Magnetization Transfer Effect
Alexey Samsonov1
1Radiology, University of Wisconsin, Madison, WI, United States
IDEAL fat/water imaging often suffers from estimation errors such as fat/water swaps, which can't be removed even by sophisticated algorithms based on field map smoothness regularization. However, these errors may be minimized by supplying the algorithms with an adequate FM prior, which, however, is not generally available. We propose a new method to improve IDEAL robustness which exploits a phenomenon of absence of magnetization transfer (MT) effect in fat for estimation of sufficiently accurate IDEAL field map prior.

Simultaneous T2, T2' and PDFF mapping in the spine using an adiabatic T2-prepared time-interleaved multi-echo gradient echo acquisition
Stefan Ruschke1, Dominik Weidlich1, Maximilian Diefenbach1, Holger Eggers2, Hendrik Kooijman3, Houchun H. Hu4, Ernst J. Rummeny1, Axel Haase5, Jan S. Kirschke6, Thomas Baum1, and Dimitrios C. Karampinos1
1Department of Diagnostic and Interventional Radiology, Technische Universität München, Munich, Germany, 2Philips Research, Hamburg, Germany, 3Philips Healthcare, Hamburg, Germany, 4Radiology, Phoenix Children’s Hospital, Phoenix, AZ, United States, 5Zentralinstitut fu¨r Medizintechnik, Technische Universität München, Garching, Germany, 6Neuroradiology, Technische Universität München, Munich, Germany
Simultaneous T2 and T2' mapping is highly desirable in applications investigating changes in blood oxygenation, iron content and bone mineral density.  Simultaneous T2 and T2' mapping is highly desirable in applications investigating blood oxygenation changes (in tumors), iron deposition (in patients with blood transfusions) and trabecular bone matrix weakening (in osteoporosis patients). Gradient echo imaging using adiabatic T2-preparation has enabled T2 mapping in the presence of inhomogeneous B1 fields. In addition, the presence of water and fat components has to be considered in the extraction of T2 and T2' parameters in many organs. The simultaneous quantification of the proton-density fat fraction (PDFF) can be also of particular interest (e.g. in the liver and in, fat fraction, bone marrow fat fraction). Multi-echo gradient echo imaging can separate water and fat components and quantify PDFF. Therefore, the purpose of the present work was to introduce a novel method for simultaneous T2, T2' and PDFF mapping, relying on an adiabatic T2-preparation combined with a time-interleaved multi-echo gradient echo acquisition scheme.

3D Whole-Heart Water Fat Coronary MRA at 3T with 100% Scan Efficiency
Gastao Cruz1, René Botnar1, and Claudia Prieto1
1Division of Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom
Fat suppression is required for visualization of coronary arteries with MRA. Studies have shown that cardiac fat may provide diagnostic information and thus water/fat coronary imaging is desirable. Respiratory motion is a major problem in whole-heart coronary imaging as respiratory gating leads to long and unpredictable scan times. Translational motion correction (TC) may be of limited value as it may introduce ghosting artefacts from static fat tissue. Here, we propose a 100% scan efficiency, two-step motion correction framework using translational and nonrigid correction for water/fat coronary MRA. The proposed approach outperforms TC, minimising ghosting artefacts from static tissues.

Free-breathing volumetric fat/water separation by combining radial sampling, compressed sensing, and parallel imaging
Thomas Benkert1,2, Daniel K. Sodickson1,2, Hersh Chandarana1,2, and Kai Tobias Block1,2
1Center for Advanced Imaging Innovation and Research (CAI2R), Department of Radiology, New York University School of Medicine, New York, NY, United States, 2Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States
This work presents a model-based fat/water separation technique for radial sampling, which takes into account the off-resonant blurring of fat and integrates both compressed sensing and parallel imaging. By combining this reconstruction scheme with 3D radial stack-of-stars sampling, volumetric and motion-robust water and fat maps as well as in-phase/opposed-phase images can be generated under free-breathing. The approach is demonstrated at 1.5T and 3T, including volunteer and patient measurements.

Rapid Water-Fat Separation using 3D VFA GRASE with Phase-Independent Reconstruction
Hahnsung Kim1 and Jaeseok Park2
1Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, Korea, Republic of, 2Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Korea, Republic of
Most water-fat separation methods based on chemical shift effect require multiple image acquisitions at different echo times, which prolong the total scanning time. Recently, to resolve aforementioned problems, variable-flip-angle (VFA) fast/turbo SE is developed. In addition, partial Fourier and/or parallel imaging techniques are incorporated with VFA fast/turbo SE imaging to speed up acquisition time but directly trade off with signal-to-noise ratio. To avoid multiple measurements and to tackle spatially variant noise amplification, we develop a novel water-fat separation method employing: 1) single-slab 3D VFA GRASE using phase-encoding blips for imaging time efficiency, 2) phase-independent reconstruction exploiting spatially complementary information along the echo direction, and 3) phase-corrected water-fat separation method using robust field distribution. 

Silicone-specific imaging using a unipolar flexible fast triple echo Dixon technique
Jingfei Ma1, Jong Bum Son1, Ken-Pin Hwang1, and Basak Dogan1
1The University of Texas MD Anderson Cancer Center, Houston, TX, United States
Silicone-specific imaging can be performed using various combinations of selective inversion, selective saturation, and Dixon methods. In this work, we propose and demonstrate a new silicone-specific imaging method with a unipolar flexible fast spin echo triple echo Dixon pulse sequence.  The method treats the water and fat signals as a single component by acquiring images only when water and fat are in-phase, and to use Dixon processing with flexible echo times to separate the remaining silicone signal. Among its many advantages, the method maintains high SNR and scan efficiency, is insensitive to field inhomogeneity, and is not subject to chemical shift misregistration.

Robust abdominal imaging with uniform fat suppression using Dixon based single shot turbo spin echo
Xinzeng Wang1, Joshua S. Greer1,2, Ivan Pedrosa1,3, Neil M. Rofsky1,3, and Ananth J. Madhuranthakam1,3
1Radiology, UT Southwestern Medical Center, Dallas, TX, United States, 2Bioengineering, University of Texas at Dallas, Richardson, TX, United States, 3Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, United States
Breath-held single shot TSE sequence is a widely used in abdominal imaging due to its speed combined with robustness to field inhomogeneities and motion. Fat suppression techniques, such as SPAIR and Dixon method are often used in SShTSE to increase the conspicuity of the anatomical details. However, SPAIR is sensitive to B0 inhomogeneity resulting in incomplete fat suppression and Dixon method requires prolonged acquisition times. In this work, we implement a dual-echo SShTSE acquisition acquiring the in-phase (IP) and out-of-phase (OP) echoes in the same repetition, providing a true single shot acquisition with robust fat/water separation.

Reproducibility of Brown Adipose Tissue Assessment in Healthy Volunteers based on Time-Resolved Dixon MRI
Vanessa Stahl1, Armin M. Nagel1,2, Martin T. Freitag3, Ralf O. Floca4, Moritz C. Berger 1, Reiner Umathum1, Mauricio Berriel Diaz5, Stephan Herzig5, Marc-André Weber6, Antonia Dimitrakopoulou-Strauss7, Peter Bachert1, Mark E. Ladd1, and Florian Maier1
1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany, 2Department of Diagnostic and Interventional Radiology, University Medical Center Ulm, Ulm, Germany, 3Department of Radiology, German Cancer Research Center, Heidelberg, Germany, 4Medical and Biological Informatics, German Cancer Research Center, Heidelberg, Germany, 5Institute for Diabetes and Cancer, Helmholtz Zentrum München German Research Center for Environmental Health, München, Germany, 6Diagnostic and Interventional Radiology, University Hospital of Heidelberg, Heidelberg, Germany, 7Clinical Cooperation Unit Nuclear Medicine, German Cancer Research Center, Heidelberg, Germany
Brown adipose tissue (BAT) is subject of ongoing metabolic and obesity research having the ability to dissipate energy through non-shivering thermogenesis. This study was performed to evaluate reproducibility of recently shown time-resolved fat-fraction (FF) MR measurements during cold exposure for BAT assessment. BAT mass and activity were compared to the previous results assessed in the interscapular BAT depots. Potential BAT depots were observed at reproducible anatomic positions, showing a reproducible FF evolution with a mean FF decrease of (-2.31±1.05)%/h during cold-activation.

A Free-breathing water/fat separation and T1, T2 quantification method using dual TR FISP in abdomen
Dongyeob Han1, Min-Oh Kim1, Honpyo Lee1, Taehwa Hong1, and Dong-Hyun Kim1
1Yonsei University, Seoul, Korea, Republic of
 A simultaneous, free-breathing water/fat separation and T1, T2 quantification method was proposed. Dual TR (in-phase and out-phase TR) and varying sinusoidal flip angle was used with FISP acquisition. For motion robustness, random rotating golden angle trajectories were applied. T1, T2 and Δφfat of fat were pre-determined using the fat dominant region mask, then water/fat signal combined dictionary was generated. The results show that the water/fraction maps from the proposed method were in good agreement with conventional breath-hold results. Furthermore, measured T1, T2 values were in good agreement with the values from the previous research.  

Improving Chemical Shift-Encoded Water-Fat Separation Based On A Detailed Consideration Of Magnetic Field Contributions
Maximilian N. Diefenbach1, Stefan Ruschke1, Hendrik Kooijman2, Anh T. Van3, Ernst J. Rummeny1, Axel Haase3, and Dimitrios C. Karampinos1
1Department of Diagnostic and Interventional Radiology, Technische Universität München, Munich, Germany, 2Philips Healthcare, Hamburg, Germany, 3Zentralinstitut fu¨r Medizintechnik, Technische Universita¨t Mu¨nchen, Munich, Germany
To avoid swaps in water-fat imaging a pre-processing step to standard fieldmap estimation methods is proposed. Based on spherical harmonic expansion the shimfield and the inhomogeneities of the main magnetic field are calculated. Thereby obtained details of the field inside the empty scanner are used to calculate an object-based fieldmap based on the tissue geometry and the susceptibility of tissue and air. The superposition of these three contributions to the fieldmap serves as an initial estimate for the water-fat separation algorithm and can reduce swaps in cases of large FOVs and when shimming is used.

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