The quality of histotripsy produced tissue lesions can be remarkably insensitive to strong acoustic aberrations: Role of nonlinear phenomena.

Abstract

Cavitation induced by short high intensity pulses can produce confined lesions with remarkably narrow transition zones (often bisecting individual cells). This process (histotripsy) is a nonlinear phenomenon wherein energetic bubble clouds are produced only when the incident ultrasound beam is above the cavitation threshold. It has been shown that acoustic aberrations in the path of an acoustic beam tend to rob energy from the main lobe raising surrounding side-lobes, sometimes significantly. However, in many cases, the shape of the main lobe, while diminished in amplitude, retains its original confined Gaussian-shaped cross-section. If the transducer-driving electronics has sufficient head-room, the main lobe can be boosted to preaberration above-threshold levels while maintaining the original main lobe profile. If the boosted main lobe amplitude is above the side-lobe levels, the lesion producing bubble clouds often are indistinguishable from the nonaberration case thus producing a clean confined lesion with little collateral damage even in the presence of strong aberrations. Confirmation of this strategy with porcine and polymer rib aberration phantoms is presented with a study of lesion shape as well as collateral damage with and without aberrations. Boosted intensities can be kept below thermally significant levels by adjusting pulse repetition frequency and pulse width.