Assessment of an image-guided histotripsy system for renal cell carcinoma

Renal cell carcinoma cancer (RCC) is the sixth most common cancer in the United States. Although surgery remains the primary treatment approach, the number of patients who qualify decreases annually due to an aging population with multiple comorbidities. An alternative to surgery is histotripsy, a non-thermal focused ultrasound technique that disrupts tissue through the generation of bubble clouds. In this study, an image-guided histotripsy system for targeting RCC was built and characterized. A focused transducer was developed with an elliptical geometry (12/9.6-cm major/minor dimensions), 8-cm focal length, and 1-MHz fundamental frequency. The transducer was capable of generating bubbles in scattering phantoms and in vivo porcine kidneys with pulses 10 cycles in duration for pulse peak negative pressures greater than 20 MPa. The transducer was equipped with a port for coaxial treatment monitoring with a curvilinear imaging probe. An image processing pipeline was developed that achieved a bubble-to-tissue ratio greater than 70 dB for ultrafast active imaging and passive detection of bubble-based emissions with a signal-to-interference ratio of 35 dB. Overall, this system has the capacity to serve as a tool for pre-clinical investigations to monitor the histotripsy treatment of RCC.