Hepatic R2* is more strongly associated with proton density fat fraction than histologic liver iron scores in patients with nonalcoholic fatty liver disease.
NAFLD; NASH; PDFF; R2*; hepatic steatosis; nonalcoholic fatty liver disease; nonalcoholic steatohepatitis; proton density fat fraction
BACKGROUND: The liver R2* value is widely used as a measure of liver iron but may be confounded by the presence of hepatic steatosis and other covariates.
PURPOSE: To identify the most influential covariates for liver R2* values in patients with nonalcoholic fatty liver disease (NAFLD).
STUDY TYPE: Retrospective analysis of prospectively acquired data.
POPULATION: Baseline data from 204 subjects enrolled in NAFLD/NASH (nonalcoholic steatohepatitis) treatment trials.
FIELD STRENGTH: 1.5T and 3T; chemical-shift encoded multiecho gradient echo.
ASSESSMENT: Correlation between liver proton density fat fraction and R2*; assessment for demographic, metabolic, laboratory, MRI-derived, and histological covariates of liver R2*.
STATISTICAL TESTS: Pearson's and Spearman's correlations; univariate analysis; gradient boosting machines (GBM) multivariable machine-learning method.
RESULTS: Hepatic proton density fat fraction (PDFF) was the most strongly correlated covariate for R2* at both 1.5T (r = 0.652, P < 0.0001) and at 3T (r = 0.586, P < 0.0001). In the GBM analysis, hepatic PDFF was the most influential covariate for hepatic R2*, with relative influences (RIs) of 61.3% at 1.5T and 47.5% at 3T; less influential covariates had RIs of up to 11.5% at 1.5T and 16.7% at 3T. Nonhepatocellular iron was weakly associated with R2* at 3T only (RI 6.7%), and hepatocellular iron was not associated with R2* at either field strength.
DATA CONCLUSION: Hepatic PDFF is the most influential covariate for R2* at both 1.5T and 3T; nonhepatocellular iron deposition is weakly associated with liver R2* at 3T only.
LEVEL OF EVIDENCE: 4 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018.
Bashir, Mustafa R; Wolfson, Tanya; Gamst, Anthony C; Fowler, Kathryn J; Ohliger, Michael; Shah, Shetal N; Alazraki, Adina; Trout, Andrew T; Behling, Cynthia; Allende, Daniela S; Loomba, Rohit; Sanyal, Arun; Schwimmer, Jeffrey; Lavine, Joel E; Shen, Wei; Tonascia, James; Van Natta, Mark L; Mamidipalli, Adrija; Hooker, Jonathan; Kowdley, Kris V; Middleton, Michael S; and Sirlin, Claude B, "Hepatic R2* is more strongly associated with proton density fat fraction than histologic liver iron scores in patients with nonalcoholic fatty liver disease." (2018). Articles, Abstracts, and Reports. 783.