A method for quantitative evaluation of steatotic liver by measurement of sound velocity change caused by ultrasonic heating has been proposed. This method utilizes the fact that the temperature coefficients of the sound velocity in fat tissue and non-fat tissue are negative and positive, respectively. This study measured the temporal rate of the sound velocity change in the TMM with a glycerin concentration of 43.00% and estimated the temperature rise due to ultrasonic heating. The temperature coefficient for the TMM was −0.41 ± 0.03 m/s/°C. The rate of sound velocity change was −0.43 ± 0.08%. As a result, the estimated temperature rise was 0.26 ± 0.04°C, when the ultrasonic heating time was 20 ms and the sound pressure was 2.0 MPa. The temperature rise due to ultrasonic heating in this method satisfies the maximum acoustic output regulation for ultrasonic diagnostic equipment, which is 1.5 °C or less. The thermal expansion of tissue due to ultrasonic heating is negligible and is not taken into account. Work supported by AMED (JP24ym0126814).
Itsubo et al. (Wed,) studied this question.