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 choice for the initial treatment, the number of patients who qualify decreases annually due to an aging population with multiple comorbidities. Histotripsy, a non-thermal focused ultrasound technique that ablates tissue through the generation of bubble clouds, has emerged as a promising non-invasive treatment for RCC. In this study, an image-guided histotripsy system for targeting RCC was build and characterized. A focused histotripsy transducer was developed with an elliptical geometry (12/9.6-cm major/minor dimensions), 8-cm focal length, and 1-MHz fundamental frequency. The acoustic field of the transducer was assessed in the linear and nonlinear regimes. Histotripsy pulses with a 10-cycle duration were capable of generating bubbles for peak negative pressures greater than 20 MPa. The transducer was equipped with a port for a curvilinear imaging probe to facilitate therapy guidance. Bubble detection was performed in a scattering phantom with ultrafast imaging. An image processing pipeline was developed that achieved a bubble-to-tissue ratio greater than 19 dB. Overall, this system has the capacity to serve as a prototype tool for both preclinical and clinical investigations into histotripsy treatment of RCC.