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

Abstract

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.