BackgroundNonalcoholic fatty liver disease (NAFLD) is increasing worldwide and is a growing cause of liver cirrhosis and cancer. The performance of the magnetic resonance elastography (MRE) visco‐elastic parameters in diagnosing progressive forms of NAFLD, including nonalcoholic steatohepatitis (NASH) and substantial fibrosis (F ≥ 2), needs to be clarified.PurposeTo assess the value of three‐dimensional MRE visco‐elastic parameters as markers of NASH and substantial fibrosis in mice with NAFLD.Study TypeProspective.Animal ModelTwo mouse models of NAFLD were induced by feeding with high fat diet or high fat, choline‐deficient, amino acid‐defined diet.Field Strength/Sequence7T/multi‐slice multi‐echo spin‐echo MRE at 400 Hz with motion encoding in the three spatial directions.AssessmentHepatic storage and loss moduli were calculated. Histological analysis was based on the NASH Clinical Research Network criteria.Statistical TestsMann–Whitney, Kruskal–Wallis tests, Spearman rank correlations and multiple regressions were used. Diagnostic performance was assessed with areas under the receiver operating characteristic curves (AUCs). P value <0.05 was considered significant.ResultsAmong the 59 mice with NAFLD, 21 had NASH and 20 had substantial fibrosis (including 8 mice without and 12 mice with NASH). The storage and loss moduli had similar moderate accuracy for diagnosing NASH with AUCs of 0.67 and 0.66, respectively. For diagnosing substantial fibrosis, the AUC of the storage modulus was 0.73 and the AUC of the loss modulus was 0.81, indicating good diagnostic performance. Using Spearman correlations, histological fibrosis, inflammation and steatosis, but not ballooning, were significantly correlated with the visco‐elastic parameters. Using multiple regression, fibrosis was the only histological feature independently associated with the visco‐elastic parameters.ConclusionMRE in mice with NAFLD suggests that the storage and loss moduli have good diagnostic performance for detecting progressive NAFLD defined as substantial fibrosis rather than NASH.Evidence Level1Technical Efficacy Stage2

Nonalcoholic steatohepatitis (NASH) and significant metabolic liver disease (MLD) are progressive forms of nonalcoholic fatty liver disease (NAFLD). MR elastography parameters have been shown to be useful for assessing NAFLD/NASH and liver inflammation. To assess the role of viscoelastic parameters in diagnosing NASH and significant MLD, MRE hepatic examinations were performed in mice with NAFLD. Our results showed that the diagnostic performance of MR elastography was higher in significant MLD than in NASH. This may be explained by inflammation and fibrosis occurring in indeterminate NASH cases included in MLD, and by poor performance of MR elastography to detect hepatocyte ballooning.