Passive and active cavitation detection methods: inception and persistence during HIFU sonication

High-intensity focused ultrasound (HIFU) is important for its application in clinical therapies. However, the phenomenon of acoustic cavitation associated with HIFU sonication in biological tissues must be carefully controlled. In this work, we aimed to investigate two aspects of this phenomenon: the generation of bubble clouds by acoustic cavitation and their evolution over time. For this study, we applied HIFU to an agar-agar phantom with exposure time of 0.6 s and driving frequency of 2 MHz. To monitor cavitation activity, we utilized both a passive and active method. A passive cavitation detector (PCD) was placed perpendicular to the HIFU transducer beam, allowing us to measure the wave from the cavitation cloud during HIFU application. Additionally, we utilized a 64-channel array to scan the phantom once HIFU ceased. Results show that both methods complement each other for the monitoring of the cavitation activity at different times during HIFU sequence. This provides information about the inception and persistence of the phenomenon, which can aid in the control and optimization of HIFU applications.