The Effect of Steatosis on Shear-Wave Velocity and Viscoelastic Properties Related to Liver Fibrosis Progression in Rat Models

Objective: Hepatic fibrosis has recently been evaluated using ultrasonography or magnetic resonance elastography. Although the shear wave velocity (SWV) obtained using point shear wave elastography (pSWE) provides a valuable measure of fibrosis, underlying steatosis may affect its measurement. Methods: Using hepatic fibrosis samples, this study evaluated the effect of steatosis on the shear wave velocity of pSWE (V-s) and viscoelastic properties (assessed by dynamic mechanical analysis) of rat liver. Fifty rats with various grades of steatosis and fibrosis underwent open abdominal in vivo V-s measurements using a commercial ultrasound scanner. The mechanical properties of hepatic tissue were also characterized under ex vivo conditions using dynamic mechanical analysis and the Zener model of viscoelasticity. Results: Fibrosis and steatosis progression influenced V-s and elasticity. The SWV computed using the Zener model and V-s showed a substantial correlation (r > 0.8). Fibrosis progression increased SWV. Steatosis was also related to SWV. Steatosis progression obscured the SWV change associated with fibrosis progression. Conclusion: We conclude that steatosis progression affects the evaluation of fibrosis progression. This finding could aid discrimination of non-alcoholic steatohepatitis from non-alcoholic fatty liver disease using SWV.