Rapid, Accurate 3-D Localization of Inertial Cavitation Events Using a Large Aperture, Narrowband, Receive-Capable Focused Ultrasound Array.

Accurate, real-time localization of cavitation events is critical for ensuring the safety and efficacy of histotripsy treatments. Current methods, such as 2-D passive acoustic mapping (PAM) and B-mode imaging, lack the necessary speed and spatial resolution for the high-treatment rates (> 100 Hz) of histotripsy. In this study, we present two computationally efficient, time-domain methods-trilateration acoustic cavitation emission (TRACE) and bandwidth-limited, large-aperture, active-acoustic, and spatio-temporal mapping (BLAST)-for rapid 3-D cavitation localization using a large-aperture, narrowband, and receive-capable focused ultrasound (US) array. TRACE estimates cavitation locations by measuring time-of-arrival (TOA) differences of cavitation collapse's shockwave emissions across an array, enabling direct localization with minimal computation. BLAST, a modified version of PAM, actively detects and time-windows collapse shockwave signals to improve processing efficiency. Experimental validation using synchronized optical imaging demonstrated submillimeter cavitation localization accuracy for both methods. TRACE achieved localization rates $\ge 100$ Hz with a computation time of 7 ms per pulse, while BLAST achieved rates exceeding 60 Hz. Results also confirmed a prefocal shift in cavitation center-of-mass relative to the array's geometric focus, highlighting the effect of focal pressure on bubble cloud dynamics. These findings suggest that TRACE and BLAST provide viable solutions for real-time 3-D cavitation monitoring, improving the precision and control of histotripsy treatments.