Expansion of the cavitation region using ultrasound focus scanning in the direction of ultrasound propagation for an efficient method of histotripsy

Abstract

Histotripsy is a non-invasive high-intensity focused ultrasound (HIFU) based therapy using mechanical effect of cavitation bubbles. In this paper, we experimentally examined the effectiveness of a proposed method of scanning the HIFU focus in the direction of propagation to expand the region of bubble cloud and increase the treatment throughput. First, the continuous generation of cavitation bubbles was observed with a high-speed camera, and it was confirmed that the region of bubble cloud generation could be expanded by focus scanning. Next, we performed ex vivo experiments. Tissue treated with histotripsy is disrupted and homogenized at subcellular level, resulting in a decrease in the backscatter intensity of the ultrasound. Therefore, we observed the progression of tissue homogenization with histotripsy by evaluating the reduction of echo intensity in ultrasound imaging. The results suggest that focus scanning can improve the time efficiency of treatment.