Noninvasive Differentiation of Simple Steatosis and Steatohepatitis by Using Gadoxetic Acid-enhanced MR Imaging in Patients with Nonalcoholic Fatty Liver Disease: A Proof-of-Concept Study

Purpose: To determine whether gadoxetic acid-enhanced magnetic resonance (MR) imaging can be used to distinguish between simple steatosis and nonalcoholic steatohepatitis (NASH) in patients with nonalcoholic fatty liver disease (NAFLD), defined according to the steatosis activity and fibrosis (SAF) scoring system, which is based on the semi-quantitative scoring of steatosis activity and liver fibrosis. Materials and Methods: The local institutional review committee approved this study and waived written informed consent. This was a retrospective study of gadoxetic acid-enhanced 3-T MR imaging performed in 81 patients with NAFLD (45 men [56%]; mean age, 56 years; range, 25-78 years). The MR images were analyzed by using the relative enhancement (the ratio of signal intensities of the liver parenchyma before and 20 minutes after intravenous administration of gadoxetic acid). Univariate and multiple regression analyses were applied to identify variables associated with relative enhancement measurements. The ability of relative enhancement to allow differentiation between simple steatosis and NASH was assessed by using area under the receiver operating characteristic (ROC) curve analysis. Results: Relative enhancement negatively correlated with the degree of lobular inflammation (r = -0.59, P < .0001), ballooning (r = -0.44, P < .0001), and fibrosis (r = -0.59, P <= .0001), but not with steatosis (r = -0.16, P = .15). Patients with NASH had a significantly lower relative liver enhancement (0.82 +/- 0.22) than those with simple steatosis (1.39 +/- 0.52) (P < .001). Relative enhancement measurements performed well in the differentiation between simple steatosis and NASH, with an area under the ROC curve of 0.85 (95% confidence interval: 0.75, 0.91) (cutoff = 1.24, sensitivity = 97%, specificity = 63%). Conclusion: Gadoxetic acid relative enhancement was significantly lower in patients with NASH than in patients with simple steatosis, but further prospective studies are warranted. (C) RSNA, 2014