Water–fat separation with IDEAL gradient‐echo imaging
ABSTRACT PurposeTo combine gradient-echo (GRE) imaging with a multipoint water–fat separation method known as “iterative decomposition of water and fat with echo asymmetry and least squares estimation” (IDEAL) for uniform water–fat separation. Robust fat suppression is necessary for many GRE imaging applications; unfortunately, uniform fat suppression is challenging in the presence of B0 inhomogeneities. These challenges are addressed with the IDEAL technique.Materials and Methods
Echo shifts for three-point IDEAL were chosen to optimize noise performance of the water–fat estimation, which is dependent on the relative proportion of water and fat within a voxel. Phantom experiments were performed to validate theoretical SNR predictions. Theoretical echo combinations that maximize noise performance are discussed, and examples of clinical applications at 1.5T and 3.0T are shown.ResultsThe measured SNR performance validated theoretical predictions and demonstrated improved image quality compared to unoptimized echo combinations. Clinical examples of the liver, breast, heart, knee, and ankle are shown, including the combination of IDEAL with parallel imaging. Excellent water–fat separation was achieved in all cases. The utility of recombining water and fat images into “in-phase,” “out-of-phase,” and “fat signal fraction” images is also discussed.ConclusionIDEAL-SPGR provides robust water–fat separation with optimized SNR performance at both 1.5T and 3.0T with multicoil acquisitions and parallel imaging in multiple regions of the body. J. Magn. Reson. Imaging 2007;25:644–652. © 2007 Wiley-Liss, Inc.
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ABSTRACT: To develop an acceleration method for MR temperature estimation using model-based proton resonance frequency (PRF) shift method.Magnetic Resonance Imaging 10/2014; 33(2). DOI:10.1016/j.mri.2014.10.006 · 2.02 Impact Factor
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ABSTRACT: Objective: To compare quantitative magnetization transfer (qMT) parameters of patellar cartilage measured using cross-relaxation imaging (CRI) in asymptomatic volunteers and patients with osteoarthritis. Design: The study was performed with Institutional Review Board approval and with all subjects signing informed consent. CRI of the knee joint was performed at 3.0T on 20 asymptomatic volunteers and 11 patients with osteoarthritis. The fraction of macromolecular bound protons (f), the exchange rate constant between macromolecular bound protons and free water protons (k), and the T-2 relaxation time of macromolecular bound protons (T-2(B)) of patellar cartilage were measured. Mann-Whitney-Wilcoxon rank-sum tests were used to compare qMT parameters between asymptomatic volunteers and patients with osteoarthritis. Results: Average f, k, and T-2(B) of patellar cartilage was 12.46%, 7.22 s(-1), and 6.49 mu s respectively for asymptomatic volunteers and 12.80%, 6.13 s(-1), and 6.80 mu s respectively for patients with osteoarthritis. There were statistically significant differences between groups of subjects for k (P < 0.01) and T-2(B) (P < 0.0001) but not f (P = 0.38) of patellar cartilage. Conclusion: Patients with osteoarthritis had significantly lower k and significantly higher T-2(B) of patellar cartilage than asymptomatic volunteers which suggests that qMT parameters can detect changes in the macromolecular matrix of degenerative cartilage.Osteoarthritis and Cartilage 10/2014; 22(10):1568-76. DOI:10.1016/j.joca.2014.06.004 · 4.66 Impact Factor