Investigation of the dependence of temperature attenuation of the layered bio-tissue

Abstract

Abstract High-intensity focused ultrasound for solid tumor ablation is a noninvasive ultrasound hyperthermia technique wherein ultrasound is transmitted through multiple layers of biological tissues, focusing on the target area. The resulting heat accumulates in the target tissue, leading to irreversible cell death or protein necrosis, achieving tumor ablation. During treatment, the efficiency of acoustic energy converting to heat is closely related to temperature attenuation in the layered tissues. To obtain an accurate prediction of thermal damage, variations in the acoustic parameters should be measured at different temperatures. This study used two methods to induce heating to the tissues: the water heating method (WHM), which involves heat transfer from the outside to the inside, and the ultrasound heating method (UHM), wherein the heat source is located inside the tissue. The finite-amplitude insertion-substitution method was utilized to determine the attenuation coefficients of various bio-tissues such as porcine fat, muscle, and liver as the temperature increased. To mitigate the effects of viscous heating artifacts, the ‘wait then measure’ (WTM) thermometric approach was utilized using wire thermocouples to measure the temperature of the ultrasound-heated tissue. Experimental results demonstrate that the attenuation coefficient of bio-tissues varies with temperature under different heating methods. This study presents the variation in tissue attenuation using WHM at 5 MHz, while tissue categories using UHM are modeled with formulas at a frequency of 2 MHz.