Mutual convolution of dual modes to enhance passive acoustic mapping for high duty-cycle HIFU exposures monitoring

Passive acoustic mapping (PAM) has been developed for cavitation detection during high intensity focused ultrasound (HIFU) treatment. Recently, Gray, et al. [1] used two separate PAM frames, acquired from two perpendicular imaging arrays to mutually filter with each other, which demonstrated the spatial resolution could be better than 1 mm that broke through the fundamental physical limitation of the conventional diagnostic array aperture for pulsed HIFU monitoring. However, the use of dual-arrays increases the complexity of the monitoring system. Also, for high duty-cycle HIFU, the computation-load of PAM as a spatial filter is much higher than pulse-echo beamformers used for B-mode. To address these concerns, the $A_{50}$ [2] of the hyperechoic area in the interleaved B-mode was used as the spatial filter to convolute with PAM for high duty-cycle HIFU monitoring to mitigate the heavy computation-load compared to mutual filtering of two separate PAM frames. Furthermore, as the hyperechoic area may occur after hundreds of cycles' sonification or never have, the $A_{50}$ of focal pressure area with primary cavitation activities that were detected as a complementary spatial filter in the absence of hyperechogenicity in the B mode.