OBJECTIVES: Chemical Shift Encoded Magnetic Resonance Imaging (CSE-MRI)-based quantification of low-level (< 5% of proton density fat fraction-PDFF) fat infiltration requires highly accurate data reconstruction for the assessment of hepatic or pancreatic fat accumulation in diagnostics and biomedical research. MATERIALS AND METHODS: We compare three software tools available for water/fat image reconstruction and PDFF quantification with MRS as the reference method. Based on the algorithm exploited in the tested software, the accuracy of fat fraction quantification varies. We evaluate them in phantom and in vivo MRS and MRI measurements. RESULTS: The signal model of Intralipid 20% emulsion used for phantoms was established for 3 T and 9.4 T fields. In all cases, we noticed a high coefficient of determination (R-squared) between MRS and MRI-PDFF measurements: in phantoms <0.9924-0.9990>; and in vivo <0.8069-0.9552>. Bland-Altman analysis was applied to phantom and in vivo measurements. DISCUSSION: Multi-echo MRI in combination with an advanced algorithm including multi-peak spectrum modeling appears as a valuable and accurate method for low-level PDFF quantification over large FOV in high resolution, and is much faster than MRS methods. The graph-cut algorithm (GC) showed the fewest water/fat swaps in the PDFF maps, and hence stands out as the most robust method of those tested.

Christian Doppler Laboratory for Clinical Molecular Imaging MOLIMA Medical University of Vienna Währinger Gürtel 18 20 1090 Vienna Austria

Department of Biomedical Engineering Columbia University Fu Foundation School of Engineering and Applied Science 1210 Amsterdam Ave New York NY 10027 USA

Department of Biomedical Imaging and Image Guided Therapy High Field MR Centre Medical University of Vienna Währinger Gürtel 18 20 1090 Vienna Austria

Division of Endocrinology and Metabolism Department of Medicine 3 Medical University of Vienna Währinger Gürtel 18 20 1090 Vienna Austria

Institute of Scientific Instruments of the CAS Kralovopolska 147 612 64 Brno Czech Republic

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Feasibility of Hepatic Fat Quantification Using Proton Density Fat Fraction by Multi-Echo Chemical-Shift-Encoded MRI at 7T