Abstract:
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Purpose: To combine a novel "Dixon" water-fat decomposition technique with CINE steady-state free precession (SSFP) cardiac imaging, to obtain uniform water-fat separation.
Methods and Materials: SSFP is a rapid imaging technique with high SNR and excellent contrast between blood and myocardium, and has gained recent widespread use for cardiac CINE imaging. SSFP is limited by the fact that water and fat both appear bright and are difficult to distinguish, possibly obscuring underlying pathology. Current fat supression techniques used with cardiac imaging and SSFP are relatively sensitive to Bo field heterogeneities. Typical "Dixon" water-fat decomposition techniques are relatively insensitive to field heterogeneities. Implementation with SSFP cardiac imaging is limited to small TE increments in order to maintain short TR, necessary to prevent image degradation from field heterogeneities. Short TE increments are not used with typical "Dixon" techniques. To address these challenges, water and fat CINE movies were decomposed with a novel iterative least-squares algorithm that was formulated for fitting data from images acquired at arbitrary (short) TE values. This algorithm requires no phase unwrapping and lends naturally to multi-coil reconstruction. Image acquisition was performed on a GE 1.5T CVI scanner with a retrospectively ECG-gated CINE SSFP sequence that sequentially obtains sets of CINE images at 3-4 TEs. A phased array torso coil was used, and imaging parameters were: TE=0.8, 1.7, 2.6ms; TR=4.7-5.0ms; FOV=32cm; slice=8mm; BW=+/-125kHz; Nx=224 (partial echo); Ny=128; views per segment=16, temporal resolution=16TR=75-80ms. 20 CINE phases were retrospectively reconstructed and breath-hold time was 20s per slice.
Results: CINE water, fat and source movies were obtained in different imaging planes (short axis, axial, 3 and 4 chamber views) from 2 normal volunteers and 4 patients. Excellent fat-water separation was obtained in all images, and distinction between pericardial fat and fluid was well demonstrated in all studies, as was fatty infiltration of the atrial septum of 1 patient.
Conclusion: Multi-coil "Dixon" techniques using an iterative least-squares fitting algorithm can be combined with SSFP cardiac CINE imaging to obtain water and fat movies with excellent fat-water separation. This facilitates improved visualization of water and fat structures within and around the heart while retaining the high CNR of SSFP imaging, and has potential for clinical applications that require uniform water-fat separation.
Reeder MD, PhD, S,
Multi-Coil Cardiac CINE Imaging with "Dixon" Fat-Water Separation and Steady-State Free Precession. Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3108408.html
