Histotripsy setup and procedure. (a) Histotripsy therapy transducer, driven by custom-built driver electronics, is interfaced with a computer which delivers histotripsy pulses to generate focal cavitation. Single focus is scanned to cover desired target volume by using motorized positioner to control movement of the therapy transducer and the imaging probe. (b) The 1 MHz histotripsy therapy transducer constructed as an 8-element ring configuration with the coaxially aligned imaging probe in the center. (c) Ultrasound imaging of the rat liver and tumor was performed prior to placing the rat on the treatment platform to determine tumor location. The tumor location is marked before the rat is placed on the treatment platform, which contains an aperture to allow the tumor region intended for treatment to be immersed in water (ultrasound coupling medium). (d) Generation of hyperechoic cavitation cloud (yellow arrow and two small circles mark the axial extent of the cavitation) in liver tumor (dashed lines).