A new cavitation suppression technique for local ablation using high-intensity focused ultrasound

When soft tissues are coagulated instantaneously during a high temperature local heating therapy for cancer using high-intensity focused ultrasound, it is extremely important to have good control over the heated area. However, scattering of the ultrasonic energy by cavitation bubbles generated by sonication degrades the heating performance at the focal spot, and there is an undesirable rise in temperature along the ultrasonic path due to the absorption of ultrasonic energy. To overcome this problem, the authors developed a new method called Cavitation Suppression Technique (CAST) to promote cavitation collapse and remove gas bubbles by sweeping the driving frequency rapidly. In this study, best conditions for CAST were obtained by comparing the effect of cavitation suppression on various driving parameters. The cavitation suppression effect and control of the heating due to field overlap (near-field heating) during focus scanning were confirmed in in vitro and in vivo experiments.