Evaluation of nonlinear imaging strategies for histotripsy monitoring

Real-time monitoring is necessary for histotripsy to ensure accurate targeting of tumors. Delineating the bubble cloud can be challenging when the tumors are deep-seated. In this talk, I will discuss collaborative work on harnessing nonlinear signal processing to visualize the histotripsy-induced bubble cloud. Specifically, we employed chirp-coded excitation, Volterra filtering, and the subharmonic component of the scattered signal to visualize the bubble cloud relative to the background. Histotripsy exposures were performed on agarose and red-blood cell-doped phantoms. The bubble cloud was visualized at ultrafast frame rates and tracked over time. Our results showed the ability of the nonlinear imaging approach to improve bubble cloud visualization relative to the background. Further, the detected cloud sizes were consistent with the treatment zone. These findings could enable the use of histotripsy for patients where the bubble cloud is not clearly visible in standard B-mode ultrasound images.