Fig. 2:

Summary of histotripsy-induced cavitation dynamics. For all forms of histotripsy, nanoscale nuclei intrinsic to the medium are present in the tissue. Left Column: For intrinsic threshold insonations, the cavitation nucleus is activated with a single-cycle pulse with tension below the intrinsic medium threshold (left arrow, middle row). The expanded bubble then undergoes an inertial collapse under ambient pressure (right arrow, middle row). Middle Column: In shock-scattering histotripsy excitations, the activated nucleus grows slowly over the course of several cycles (left arrow, middle row) and deforms due to the incident shock waves (right arrow, middle row). Additional bubbles form spatially and temporally in regions of constructive interference between the incident wave, and waves scattered by the deformed bubble. Right column: In boiling histotripsy, shock-enhanced heating alters cavitation nucleus (left arrow, middle tow) to reduce the requisite tension for bubble formation (right arrow, middle row). For all forms of histotripsy, the expansion and contraction of the bubble imparts lethal strain on the cellular and extracellular components of the tissue in close proximity to the bubble (depicted in left column, middle row only). Representative frames from high speed videography of histotripsy-generated bubbles are shown in the bottom row. Note: Bubble sizes and nuclei in second row not to scale.