# Temporal Change Rate in Sound Velocity Caused by Ultrasonic Heating for Evaluation of Steatotic Liver

## TL;DR

This study explores a noninvasive ultrasound-based method to detect steatotic liver diseases by measuring sound velocity changes caused by heating.

## Contribution

The novel contribution is using ultrasonic heating to measure sound velocity change rates for diagnosing steatotic liver disease.

## Key findings

- In vitro and in vivo measurements showed positive change rates in sound velocity for normal livers and negative for steatotic livers.
- The sound velocity change rate decreased with increasing lipid accumulation, as demonstrated using tissue-mimicking materials with glycerol.
- Results suggest that thermophysical properties can distinguish normal from steatotic livers.

## Abstract

The prevalence of steatotic liver diseases is on the rise globally, with metabolic dysfunction-associated steatohepatitis being a significant concern due to its potential to lead to irreversible fibrosis. This study investigated a noninvasive method of diagnosing steatotic liver diseases using ultrasound. It is known that the sound velocity of fat tissue decreases with heating, whereas that of non-fat tissue increases with heating. Therefore, the change rates in sound velocity were measured in vitro and in vivo on mouse livers from the control and steatotic liver groups by ultrasonic heating within safety standards. In both in vitro and in vivo measurements, there were positive values in the control group and negative values in the steatotic liver group. The results of these change rates in sound velocity indicated that it is possible to determine whether the liver is normal or steatotic.

Steatotic liver diseases are increasing globally, with metabolic dysfunction-associated steatohepatitis potentially causing irreversible fibrosis progression. This study focuses on an ultrasonic diagnostic method for steatotic liver disease based on temperature dependence of sound velocity for tissue characterization. Since the temperature coefficient of sound velocity in liver is expected to decrease with increasing lipid accumulation, the temperature coefficient of sound velocity in tissue-mimicking material as a function of glycerol concentration was measured. It decreased as glycerol concentration increased, changing from positive to negative value at 37.5% glycerol concentration. Change rates in sound velocity by ultrasonic heating were then measured in vitro on liver left lobes of mice with steatotic liver induced by choline-deficient, L-amino acid-defined, and high-fat diet. There were positive values in the control group, whereas there were negative values in the steatotic liver group. In vivo measurements of mouse livers using an electrocardiogram-synchronized system showed similar results, with positive values in the control group and negative values in the steatotic liver group. Thermophysical properties can determine whether the liver is normal or steatotic. However, to estimate the lipid accumulation rate from the change rate in sound velocity, it is necessary to reduce the measurement variation.