Differential PI-Based Subharmonic Cavitation Imaging During Pulsed High Intensity Focused Ultrasound Exposures

Cavitation monitoring and imaging is necessary for high intensity focused ultrasound therapy (HIFU) especially for pulsed HIFU (pHIFU). This paper developed a differential PI- based subharmonic imaging technique to monitor cavitation bubble activities during pulsed HIFU exposures. The method is a combination of differential imaging and PI- based subharmonic imaging, and it was validated by in vitro porcine muscle experiments. The effects of parameters of pHIFU on cavitation activities, including pulse length and duty cycle, were studied using the differential PI- based subharmonic imaging. It was found that the greater was the cavitation degree the greater the randomness of cavitation was, and the longer was the pulse length the more effect on cavitation activities the duty cycle would have. On the whole, the cavitation bubbles would accumulate with pHIFU exposure number of times approximately following a linear law.