Histotripsy: An overview

Abstract

Histotripsy produces non-thermal lesions by generating dense highly confined energetic bubble clouds that mechanically fractionate tissue. This nonlinear thresholding phenomenon has useful consequences. If only the tip of the waveform (P-) exceeds the intrinsic threshold*, small lesions less than the diffraction limit can be generated. This is called microtripsy (other presentations in this session). Moreover, side lobes from distorting aberrations can be “thresholded-out” wherein part of the main lobe exceeds the intrinsic threshold producing a clean bubble cloud (and lesion) conferring significant immunity to aberrations. If a high frequency probe (imaging) waveform intersects a low frequency pump waveform, the compounded waveform can momentarily exceed the intrinsic threshold producing a lesion with an imaging transducer. Multi-beam histotripsy (other presentations in this session) allows flexible placement of both pump and probe transducers. Very broadband P- “monopolar” pulses*, ideal for histotripsy, can be synthesized in a generalization of the multi-beam histotripsy (other presentations in this session) case wherein very short pulses from transducer elements of many different frequencies are added at the focus of what is called a frequency compounding transducer (other presentations in this session). Ultrasound image guidance works well with histotripsy. Bubble clouds are easily seen simplifying both lesion targeting and continuous validation of the ongoing process. Hypoechoic homogenized tissue allows real-time quantification of lesion formation.