Reproducibility of MR‐based liver fat quantification across field strength: Same‐day comparison between 1.5T and 3T in obese subjects

PURPOSE: To examine the reproducibility of quantitative magnetic resonance (MR) methods to estimate hepatic proton density fat-fraction (PDFF) at different magnetic field strengths. MATERIALS AND METHODS: This Health Insurance Portability and Accountability Act (HIPAA)-compliant study was approved by the Institutional Review Board. Following informed consent, 25 severely obese subjects (mean body mass index BMI: 45 ± 4, range: 38-53 kg/m(2) ) were scanned at 1.5T and 3T on the same day. Two confounder-corrected multiecho chemical shift-encoded gradient-echo-based imaging methods were acquired to estimate PDFF over the entire liver: 3D complex-based (MRI-C) and 2D magnitude-based (MRI-M) MRI. Single-voxel MR spectroscopy (MRS) was performed in the right liver lobe. Using linear regression, pairwise comparisons of estimated PDFF were made between methods (MRI-C, MRI-M, MRS) at each field strength and for each method across field strengths. RESULTS: 1.5T vs. 3T regression analyses for MRI-C, MRI-M, and MRS PDFF measurements yielded R(2) values of 0.99, 0.97, and 0.90, respectively. The best-fit line was near unity (slope(m) = 1, intercept(b) = 0), indicating excellent agreement for each case: MRI-C (m = 0.92 0.87, 0.99, b = 1.4 0.7, 1.8); MRI-M (m = 1.0 0.90, 1.08, b = -1.4 -2.4, -0.5); MRS (m = 0.98 0.82, 1.15, b = 1.2 -0.2, 3.0). Comparing MRI-C and MRI-M yielded an R(2) = 0.98 (m = 1.1 1.02, 1.16, b = -1.8 -2.8, -1.1) at 1.5T, and R(2) = 0.99 (m = 0.98 0.93, 1.03, b = 1.2 0.7, 1.7) at 3T. CONCLUSION: This study demonstrates that PDFF estimation is reproducible across field strengths and across two confounder-corrected MR-based methods.