Acoustic streaming effect on flow and heat transfer in porous tissue during exposure to focused ultrasound

High-intensity focused ultrasound (HIFU) is a minimally invasive technique of regional treatment in which ultrasound waves are focused on targeted tissue. Nevertheless, the precise localization of the target area of HIFU ablation remains challenging. This study investigated acoustic pressure, fluid flow, and heat transfer in porous tissue during exposure to HIFU. The effects of the heat transfer model, tissue permeability, and exposure time on fluid flow and temperature distribution in the tissue were numerically investigated. Additionally, the heating-region shape and heating position were studied. The acoustic pressure, fluid flow, and temperature distributions in the porous tissue during exposure to HIFU were calculated using the numerical simulation of acoustic wave propagation and heat transfer models. The heat transfer models used were formulated based on the conventional bioheat model and porous media theory. With the porous media model, the temperature distributions were observed to be different from those of the conventional bioheat model; this was caused by the acoustic streaming effect. Permeability affected the flow pattern and temperature distribution in the tissue. In particular, tissue permeability also has a significant effect on the position of the target area and lesion shape within the tissue.