Role of high-frame-rate imaging for monitoring high-intensity focused ultrasound treatment

During high-intensity focused ultrasound (HIFU) treatment, tissue change, and acoustic cavitation as its precursor, should be monitored both in and outside the HIFU focal zone, to ensure the intended therapeutic effect and to prevent potential adverse effects, respectively. Unlike boiling-induced bubbles, cavitation-generated microbubbles are difficult to detect with conventional B-mode imaging because their life is significantly shorter than the typical image repetition period. An image repetition period less than a few milliseconds is required to detect them. This can only be accomplished by high-frame-rate imaging with plane or diverging waves. In-vivo as well as ex-vivo experimental results evidencing the effectiveness of such imaging to detect cavitation-generated microbubbles will be shown in this paper. A number of researches are underway to ultrasonically detect HIFU-induced tissue change, which occurs at much lower temperature than boiling. During echo data acquisition for detecting such tissue c...