Viscoelasticity and shear wave velocity of liver tissue evaluated by dynamic mechanical analysis

The frequency dependence of shear wave velocity provides significant information for evaluating viscoelastic character of tissue relating to liver fibrosis. Although Voigt model has been often used in viscoelastic analysis, several studies showed that the frequency dependence measured by dynamic mechanical analysis (DMA) test was not consistent with the theoretical prediction. To experimentally investigate the relationships of the change of the tissue structure and the viscoelasticity of tissue, the shear wave velocity of fatty and fibrotic livers of rat model was quantitatively measured by using shear wave elastography (SWE) and DMA test. In DMA test, shear wave velocity was calculated from the complex elasticity modulus; storage and loss elastic modulus. The difference in shear wave velocity between fatty and fibrotic livers was evaluated to be 0.27 m/s in SWE and 0.20 m/s in DMA test.