Thermal lesion development in bubble‐mediated HIFU: modeling

Fast heat deposition during high‐intensity focused ultrasound (HIFU) therapy is often accompanied by acoustic cavitation. In vivo and in vitro experiments have shown that with cavitation the heating rate is greatly enhanced and HIFU efficacy can be favorably improved. However uncontrolled cavitation usually results in irregular lesions and other undesirable effects. This work studies the interaction between the ultrasound pressure, cavitation and temperature field in a medium containing cavitation bubbles, with size distribution estimated by stability criteria and number density estimated from empirical observations. Treating the bubbly mixture as an effective medium with effective sound speed and attenuation coefficient determined from bubble dynamics, iterative computations on acoustic propagation and subsequent cavitation and thermal effects can be performed. The thermal lesion development is then simulated in a tissue‐like medium exposed to 1‐MHz HIFU in CW with MPa pressure amplitudes, and compared with experiment