Receiving acoustic emissions from cavitation bubbles to correct phase aberration and reduce rib heating during transabdominal histotripsy

In transabdominal histotripsy, tissues with varying speed of sound defocus ultrasound pulses, causing phase aberrations that distort and weaken the ultrasound beam focus. Additionally, intervening ribs strongly absorb ultrasound, causing local tissue heating. Together, these effects limit the safety and efficacy of histotripsy treatments. This talk will present work using the phase and amplitude information from cavitation emissions received by a therapy phased array to (1) determine and correct phase aberrations and (2) to detect and de-activatearray elements that cause heating at the ribs. In vitro experiments with excised porcine abdominal tissues showed that phase corrections determined from received cavitation emissions can restore focusing quality and recover nearly all focal pressure amplitude lost to aberration. In vivo, cavitation signal-based aberration correction improved focusing in the porcine liver to reduce the input acoustic power required to perform histotripsy by 26%, on average. Additionally, by analyzing the amplitude of received cavitation emissions, elements blocked by ribs were detected and turned off to reduce rib heating rates in vitro by as much as a factor of two while maintaining equivalent focal pressure. These results suggest that adaptive re-focusing methods based on received cavitation signals could help improve the safety and efficacy of transabdominal histotripsy treatments.