Acoustic cavitation detection in biomedical and underwater systems

In the past decade, significant progress has been made in detecting and localizing cavitation for treatment monitoring in biomedical acoustics. Here, we compare passive cavitation imaging (PCI) and passive cavitation detection (PCD) during histotripsy in tissue-mimicking polyacrylamide (PA) hydrogels; PCI and bubble Doppler ultrasound are also used to evaluate flow-induced cavitation in a water tunnel. A Philips/ATL L7-4 transducer driven with a research ultrasound system was used for both PCI and Doppler imaging; a Sonic Concepts Y-107 transducer was used for PCD. PA hydrogels were treated with 1.5 MHz focused ultrasound (10-ms pulses with p + = 127 MPa/p− = 35 MPa repeated at 1-Hz for 60 s). In the 12-in. water tunnel, cavitation on a 1-in. diameter steel cylinder was imaged through a 0.5-inch-thick acrylic window while flow increased from 30–35 ft/s. High-speed cameras were also used in both experiments. In PA hydrogels, cavitation was observed with both PCI and PCD, although signal trends differed over the treatment. In the water tunnel, both PCI and Doppler ultrasound detected and localized cavitation events such as the horseshoe vortex, with measured amplitudes increasing with flow speed. These results show that cavitation imaging can be applied to multiple areas of acoustics. [Tissue work supported by NIHR01EB032860].