• Charlie C Park, Catherine Hooker, Jonathan C Hooker, Emily Bass, William Haufe, Alexandra Schlein, Yesenia Covarrubias, Elhamy Heba, Mark Bydder, Tanya Wolfson, Anthony Gamst, Rohit Loomba, Jeffrey Schwimmer, Diego Hernando, Scott B Reeder, Michael Middleton, Claude B Sirlin, and Gavin Hamilton.
• Liver Imaging Group, Department of Radiology, University of California at San Diego, La Jolla, California, USA.
• J Magn Reson Imaging. 2019 Jan 1; 49 (1): 229-238.

BackgroundImproving the signal-to-noise ratio (SNR) of chemical-shift-encoded MRI acquisition with complex reconstruction (MRI-C) may improve the accuracy and precision of noninvasive proton density fat fraction (PDFF) quantification in patients with hepatic steatosis.PurposeTo assess the accuracy of high SNR (Hi-SNR) MRI-C versus standard MRI-C acquisition to estimate hepatic PDFF in adult and pediatric nonalcoholic fatty liver disease (NAFLD) using an MR spectroscopy (MRS) sequence as the reference standard.Study TypeProspective.Population/SubjectsIn all, 231 adult and pediatric patients with known or suspected NAFLD.Field Strength/SequencePDFF estimated at 3T by three MR techniques: standard MRI-C; a Hi-SNR MRI-C variant with increased slice thickness, decreased matrix size, and no parallel imaging; and MRS (reference standard).AssessmentMRI-PDFF was measured by image analysts using a region of interest coregistered with the MRS-PDFF voxel.Statistical TestsLinear regression analyses were used to assess accuracy and precision of MRI-estimated PDFF for MRS-PDFF as a function of MRI-PDFF using the standard and Hi-SNR MRI-C for all patients and for patients with MRS-PDFF <10%.ResultsIn all, 271 exams from 231 patients were included (mean MRS-PDFF: 12.6% [SD: 10.4]; range: 0.9-41.9). High agreement between MRI-PDFF and MRS-PDFF was demonstrated across the overall range of PDFF, with a regression slope of 1.035 for the standard MRI-C and 1.008 for Hi-SNR MRI-C. Hi-SNR MRI-C, compared to standard MRI-C, provided small but statistically significant improvements in the slope (respectively, 1.008 vs. 1.035, P = 0.004) and mean bias (0.412 vs. 0.673, P < 0.0001) overall. In the low-fat patients only, Hi-SNR MRI-C provided improvements in the slope (1.058 vs. 1.190, P = 0.002), mean bias (0.168 vs. 0.368, P = 0.007), intercept (-0.153 vs. -0.796, P < 0.0001), and borderline improvement in the R2 (0.888 vs. 0.813, P = 0.01).Data ConclusionCompared to standard MRI-C, Hi-SNR MRI-C provides slightly higher MRI-PDFF estimation accuracy across the overall range of PDFF and improves both accuracy and precision in the low PDFF range.Level Of Evidence1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:229-238.© 2018 International Society for Magnetic Resonance in Medicine.

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