MRI‐Based Quantitative R2 Mapping at 3 Tesla Reflects Hepatic Iron Overload and Pathogenesis in Nonalcoholic Fatty Liver Disease Patients

Background The role of hepatic iron overload (HIO) in nonalcoholic fatty liver disease (NAFLD) pathogenesis has not been fully elucidated. Purpose This study aimed to investigate the effect of HIO and examine the diagnostic usefulness of magnetic resonance imaging (MRI)‐based R2* quantification in evaluating hepatic iron content (HIC) and pathological findings in NAFLD. Study Type Prospective and retrospective. Population A prospective study of 168 patients (age, 57.2 ± 15.0; male/female, 80/88) and a retrospective validation study of 202 patients (age, 57.0 ± 14.4; male/female, 113/89) with liver‐biopsy‐confirmed NAFLD were performed. Field Strength/Sequence 3 T; chemical‐shift encoded multi‐echo gradient echo. Assessment Using liver tissues obtained by liver biopsy, HIC was prospectively evaluated in 168 patients by atomic absorption spectrometry. Diagnostic accuracies of HIC and R2* for grading hepatic inflammation plus ballooning (HIB) as an indicator of NAFLD activity were assessed. Statistical Tests Student's t‐test and analysis of variance (ANOVA) with Scheffe's multiple testing correction for univariate comparisons; multivariate logistic analysis. P‐value less than 0.05 is statistically significant. Results HIC was significantly correlated with HIB grades (r = 0.407). R2* was significantly correlated with HIC (r = 0.557) and HIB grades (r = 0.569). R2* mapped an area under the receiver operating characteristic (AUROC; 0.774) for HIC ≥808 ng/mL (median value) with cutoff value of 62.5 s−1. In addition, R2* mapped AUROC of HIB for grades ≥3 was 0.799 with cutoff value of 58.5 s−1. When R2* was