• B Dustin Pooler, Diego Hernando, Jeannine A Ruby, Hiroshi Ishii, Ann Shimakawa, and Scott B Reeder.
• Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA.
• J Magn Reson Imaging. 2018 Dec 1; 48 (6): 1578-1585.

BackgroundCurrent chemical-shift-encoded (CSE) MRI techniques for measuring hepatic proton density fat fraction (PDFF) are sensitive to motion artifacts.PurposeInitial validation of a motion-robust 2D-sequential CSE-MRI technique for quantification of hepatic PDFF.Study TypePhantom study and prospective in vivo cohort.PopulationFifty adult patients (27 women, 23 men, mean age 57.2 years).Field Strength/Sequence3D, 2D-interleaved, and 2D-sequential CSE-MRI acquisitions at 1.5T.AssessmentThree CSE-MRI techniques (3D, 2D-interleaved, 2D-sequential) were performed in a PDFF phantom and in vivo. Reference standards were 3D CSE-MRI PDFF measurements for the phantom study and single-voxel MR spectroscopy hepatic PDFF measurements (MRS-PDFF) in vivo. In vivo hepatic MRI-PDFF measurements were performed during a single breath-hold (BH) and free breathing (FB), and were repeated by a second reader for the FB 2D-sequential sequence to assess interreader variability.Statistical TestsCorrelation plots to validate the 2D-sequential CSE-MRI against the phantom and in vivo reference standards. Bland-Altman analysis of FB versus BH CSE-MRI acquisitions to evaluate robustness to motion. Bland-Altman analysis to assess interreader variability.ResultsPhantom 2D-sequential CSE-MRI PDFF measurements demonstrated excellent agreement and correlation (R2 > 0.99) with 3D CSE-MRI. In vivo, the mean (±SD) hepatic PDFF was 8.8 ± 8.7% (range 0.6-28.5%). Compared with BH acquisitions, FB hepatic PDFF measurements demonstrated bias of +0.15% for 2D-sequential compared with + 0.53% for 3D and +0.94% for 2D-interleaved. 95% limits of agreement (LOA) were narrower for 2D-sequential (±0.99%), compared with 3D (±3.72%) and 2D-interleaved (±3.10%). All CSE-MRI techniques had excellent correlation with MRS (R2 > 0.97). The FB 2D-sequential acquisition demonstrated little interreader variability, with mean bias of +0.07% and 95% LOA of ± 1.53%.Data ConclusionThis motion-robust 2D-sequential CSE-MRI can accurately measure hepatic PDFF during free breathing in a patient population with a range of PDFF values of 0.6-28.5%, permitting accurate quantification of liver fat content without the need for suspended respiration.Level Of Evidence1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:1578-1585.© 2018 International Society for Magnetic Resonance in Medicine.

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