Acoustic cavitation localization during histotripsy using transmit-receive capable arrays

The nucleation and collapse of cavitation generated during histotripsy results in point-like emissions of shockwaves. Owing to the short duration acoustic pulses utilized during histotripsy the acoustic background from pulse reflections off intervening tissues is minimal and temporally isolated. This allows acoustic cavitation emission (ACE) shockwaves to be differentiated from the background in measured signals using simplified approaches such as peak detection and time gating, even in signals acquired using narrow bandwidth receivers such as the transmitting elements of the histotripsy array. The array elements allow acquisitions from across the array's entire aperture, which in turn allows cavitation to be localized in 3D. Here we describe multiple methods for localizing cavitation and evaluating induced tissue damage based on ACE signals measured using transmit-receive capable histotripsy arrays. The speed and accuracy of the methods were evaluated in ex vivo and in vitro experiments. Cavitation could be localized in 3D at rates >100Hz. Mean localization errors, with respect to measurements from optical images, were <2 mm (approximately the diameter of the generated bubbles). Cavitation lifespans could be assessed concurrently with the bubbles' 3D locations and correlated well with histological observations of induced damage, allowing 3D assessments of damage.