Boiling histotripsy of the kidney: Preliminary studies and predictors of treatment effectiveness

Abstract

Boiling histotripsy (BH), an ultrasound technique to mechanically homogenize tissue, has been described in ex vivo liver and myocardium. As a noninvasive, non-thermal based approach, BH may have advantages over clinically available thermal ablative technologies for renal masses. We aimed to characterize BH exposures in human and porcine ex vivo kidneys using a 7-element 1 MHz transducer (duty factor 1–3%, 5–10 ms pulses, 98 MPa in situ shock amplitude, 17 MPa peak negative). Lesions were successfully created in both species, demonstrating focally homogenized tissue above treatment thresholds (pulse number) with stark transition between treated and untreated cells on histologic assessment. Human tissue generally required more pulses to produce similar effect compared to porcine. Similarly, kidneys displayed tissue specific resistance to BH with increasing resistance from cortex to medulla to the collecting system. Tissue properties that predict resistance to renal BH were evaluated demonstrating correlation between tissue collagen content and tissue resistance. Subsequently, the impact of intervening abdominal wall and ribs on lesion generation ex vivo was evaluated. “Transabdominal” and “transcostal” treatment required approximately 5- and 20-fold greater acoustic power, respectively, to elicit boiling vs. no intervening tissue. [Work supported by NIH T32DK007779, R01EB007643, K01EB015745 and NSBRI through NASA NCC 9-58.]