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/m2) 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 R2 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 R2 = 0.98 (m = 1.1 [1.02, 1.16], b = –1.8 [–2.8, −1.1]) at 1.5T, and R2 = 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. J. Magn. Reson. Imaging 2015;42:811–817.