Diffusion-weighted magnetic resonance imaging for the staging of liver fibrosis

Background: Diffusion-weighted magnetic resonance (MR) imaging (DWI) has been suggested for staging liver fibrosis. The aim of this study was to evaluate the diagnostic accuracy of DWI for the noninvasive assessment of hepatic fibrosis. Methods: We retrospectively compared DWI from clinically acquired MR scans with histologic methods. Liver biopsy specimens were staged F0-F4 in accordance with the METAVIR score. Hepatic steatosis was classified on a 5-point scale. Hepatic iron was graded on a 3-point scale. Liver inflammation was scored according to the modified hepatic activity index. Nonparametric methods, linear regression models, and receiver operating characteristic analyses were used to determine diagnostic accuracy and apparent diffusion coefficient (ADC) cutoff values. Results: Liver ADC values were inversely correlated with fibrosis stage: P=-0.54 (P<0.0001). Although there was substantial overlap in the ADC distributions, the differences in ADC values by METAVIR stages F0 versus (vs.) F1-4, F0-1 versus F>1, F0-2 versus F3-4 and F0-3 versus F4 were all significant. For prediction of fibrosis stage 1, stage 2, stage 3, and stage 4 area under the receiver operating characteristic curve of 0.79, 0.77, 0.77, and 0.79 were obtained, respectively. Inflammation also correlated significantly with ADC values (P=-0.23, P=0.03), but iron content (P=0.17) or steatosis (P=0.63) did not correlate with ADC measurements. Conclusions: Liver ADC can be used to predict liver fibrosis with acceptable diagnostic accuracy. DWI should be included in further prospective studies to validate a comprehensive MR imaging protocol for the noninvasive assessment of hepatic fibrosis.