Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : November 12, 2022 - November 13, 2022
High Intensity Focused Ultrasound (HIFU) is utilized for a minimal invasive method to ablate tumors by the temperature rise at the focal point of the focused ultrasound. In HIFU therapy, the treatment time tends to be long due to the narrow region of the ablation. Hence, the ways to enhance the efficiency of HIFU therapy have been studied, and the usage of a dense cavitation bubble cloud is expected to enhance energy dissipation from acoustic energy to heat. However, the cavitation cloud may cause the damage of surrounding tissue due to shockwaves when it collapses. Therefore, it is necessary to control cavitation clouds for effective usage. Ogasawara et al. (2018) investigated the cavitation cloud formation in water by using a laser-induced bubble as a reflector of HIFU. In the present study, we investigate the influence of medium elasticity on the cavitation cloud formation by the backscattering of HIFU from microbubbles created by a focused laser beam in the elastic medium. As a tissue mimicking phantom, agarose gel is chosen because of its high optical clarity for photography and its wide usage in tissue engineering. Medium elasticity varies from approximately 2.7 kPa to 200 kPa. By using residual microbubbles in the gel as reflectors of HIFU, the cavitation cloud generation point can be controlled. It is shown that as gel stiffness increases, the maximum value of the top interface position of cavitation clouds decreases and the collapse time of cavitation clouds becomes shorter.
