Evaluation of shear wave dispersion caused by fibrous structure and tissue viscosity using hepatic fibrosis progression and histological models

Shear wave elasticity imaging has been utilized for chronic hepatitis diagnosis. The relationship between hepatic fibrosis and elasticity or viscosity has been described recently. Therefore, it is expected that viscosity analysis will improve the accuracy of staging fibrosis, in addition to elasticity measuring. However, fibrous structures affect dispersion slope analysis, so it is necessary to investigate the effect of fibrous structure on dispersion slope analysis. In order to simulate shear wave propagation in liver tissue, we use two types of models representing fibrosis progression. One is created using a potential function, and the other is created from hepatic histological sections. Simulating shear wave propagation in these models without viscosity in order to examine the effect of fibrous structure alone, dispersion analysis was applied to the particle velocity data. We evaluated the dispersion slope and shear wave phase velocity at 200 Hz (c (200 Hz)). In both models, the dispersion slope increased significantly with fibrosis progression. The resulting dispersion slope is about 30% of the dispersion slope in in vivo measurements, indicating that the effect of fibrous structure is large enough for viscosity analysis.