Free-breathing 3D stack-of-radial MRI quantification of liver fat and R₂* in adults with fatty liver disease

Purpose: To investigate the agreement, intra-session repeatability, and inter-reader agreement of liver proton-density fat fraction (PDFF) and R₂* quantification using free-breathing 3D stack-of-radial MRI, with and without self-gated motion compensation, compared to reference breath-hold techniques in subjects with fatty liver disease (FLD).

Methods: In this institutional review board-approved prospective study, thirty-eight adults with FLD and/or iron overload (24 male, 58 ± 12 years) were imaged at 3T using free-breathing stack-of-radial MRI, breath-hold 3D Cartesian MRI, and breath-hold single-voxel MR spectroscopy (SVS). Each sequence was acquired twice in random order. To assess agreement compared to reference breath-hold techniques, the dependency of liver PDFF and/or R₂* quantification on the sequence, radial sampling factor, and radial self-gating temporal resolution was assessed by calculating the Bayesian mean difference (MD_B) of the posteriors. Intra-session repeatability and inter-reader agreement (two independent readers) were assessed by the coefficient of repeatability (CR) and intraclass correlation coefficient (ICC), respectively.

Results: Thirty-five participants (21 male, 57 ± 12 years) were included for analysis. Both free-breathing radial MRI techniques (with and without self-gating) achieved ICC ≥ 0.92 for quantifying PDFF and R₂*, and quantified PDFF with MD_B < 1.2% compared to breath-hold techniques. Free-breathing radial MRI required self-gating to accurately quantify R₂* (MD_B < 10s^-1 with self-gating; MD_B < 50s^-1 without self-gating). The radial sampling factor affected PDFF and R₂* quantification while the radial self-gating temporal resolution only affected R₂* quantification. Repeated self-gated free-breathing radial MRI scans achieved CR < 3% and CR < 27 s^-1 for PDFF and R₂*, respectively.

Conclusion: A free-breathing stack-of-radial MRI technique with self-gating demonstrated agreement, repeatability, and inter-reader agreement compared to reference breath-hold techniques for quantification of liver PDFF and R₂* in adults with FLD.