Real-Time Monitoring and Quantitative Evaluation of Cavitation Bubbles Induced by High Intensity Focused Ultrasound Using B-Mode Imaging

A software-based method is proposed to eliminate the flooding interference strips in B-mode images, and to evaluate the cavitation bubbles generated during high intensity focused ultrasound (HIFU) exposures. In vitro tissue phantoms are exposed to 1.12 MHz HIFU pulses with a fixed 100 Hz pulse repetition frequency. HIFU-induced cavitation bubbles are detected as hyperechoic regions in B-mode images. The temporal evolution of cavitation bubbles, generated by HIFU pulses with varying driving amplitude and pulse length, is analyzed by measuring the time-varying area of the hyperechoic region. The results show that: first, it is feasible to monitor HIFU-induced cavitation bubble activity in real-time using B-mode imaging; second, more cavitation bubbles can be generated with higher acoustic energy delivered; third, the hyperechoic region is observed to shrink gradually after ceasing the HIFU pulses, which indicates the dissolution of cavitation bubbles. This work will be helpful for developing an effective tool to realize real-time monitoring and quantitative evaluation of HIFU-induced cavitation bubble activity using a current commercialized B-mode machine.