Fat and fibrosis as confounding cofactors in viscoelastic measurements of the liver

TL;DR

This study investigates how fat and fibrosis affect viscoelastic measurements of the liver, revealing their joint influence on shear wave speed and attenuation, which is crucial for accurate liver disease assessment.

Contribution

It provides a comprehensive analysis combining theory, experiments, and simulations to quantify fat and fibrosis effects on liver viscoelastic measurements.

Findings

Fat and fibrosis jointly influence shear wave speed and attenuation.

Fibrosis stages significantly affect shear wave attenuation at constant fat levels.

The rate of shear wave attenuation increase with fat varies with fibrosis stage.

Abstract

Elastography provides significant information on staging of fibrosis in patients with liver disease and may be of some value in assessing steatosis. However, there remain questions as to the role of steatosis and fibrosis as cofactors influencing the viscoelastic measurements of the liver tissues, particularly shear wave speed (SWS) and shear wave attenuation (SWA). In this study, by employing the theory of composite elastic media as well as two independent experimental measurements on fat-in-gelatin phantoms and also finite element simulations, it is consistently shown that fat and fibrosis jointly influence the SWS and SWA measurements. At a constant level of fat, fibrosis stages can influence the SWA by factors of 2-4. Moreover, the rate of increase in SWA with increasing fat is strongly influenced by the stages of fibrosis; softer background cases (low fibrosis stages) have higher rate of SWA increase with fat than those with stiffer moduli (higher fibrosis stages). Meanwhile, SWS results are influenced by the presence of fat, however the degree of variability is more subtle. The results indicate the importance of jointly considering fat and fibrosis as contributors to SWS and SWA measurements in complex liver tissues and in the design and interpretation of clinical trials.