Interexamination repeatability and spatial heterogeneity of liver iron and fat quantification using MRI-based multistep adaptive fitting algorithm

Abstract

Purpose To assess the interexamination repeatability and spatial heterogeneity of liver iron and fat measurements using a magnetic resonance imaging (MRI)-based multistep adaptive fitting algorithm. Materials and Methods This prospective observational study was Institutional Review Board-approved and Health Insurance Portability and Accountability Act-compliant. Written informed consent was waived. In all, 150 subjects were imaged on 3T MRI systems. A whole-liver volume acquisition was performed twice using a six-echo 3D spoiled gradient echo sequence during two immediately adjacent examinations. Colocalized regions of interest (ROIs) in three different hepatic segments were placed for R2∗ and proton density fat fraction (PDFF) measurements by two readers independently. Mean R2∗ and PDFF values between readers and acquisitions were compared using the Wilcoxon signed-rank test, intraclass correlation coefficients (ICCs), linear regression, Bland-Altman analysis, and analysis of variance (ANOVA). Results The mean R2∗ and PDFF values across all ROIs and measurements were 51.2±25.2 s-1 and 6.9±6.4%, respectively. Mean R2∗ and PDFF values showed no significant differences between the two acquisitions (P=0.05-0.87). Between the two acquisitions, R2∗ and PDFF values demonstrated almost perfect agreement (ICCs=0.979-0.994) and excellent correlation (R2=0.958-0.989). Bland-Altman analysis also demonstrated excellent agreement. In the ANOVA, the individual patient and ROI location were significant effects for both R2∗ and PDFF values (P<0.05). Conclusion MRI-based R2∗ and PDFF measurements are repeatable between examinations. Between-measurement changes in R2∗ of more than 10.1 s-1 and in PDFF of more than 1.7% are likely due to actual tissue changes. Liver iron and fat content are variable between hepatic segments.