Robotically-Assisted Sonic Therapy for Renal Ablation in a Live Porcine Model: Initial Preclinical Results

Purpose: To demonstrate the feasibility of Robotically Assisted Sonic Therapy (RAST)-a noninvasive and nonthermal focused ultrasound therapy based on histotripsy-for renal ablation in a live porcine model. Materials and Methods: RAST ablations (n = 11) were performed in 7 female swine: 3 evaluated at 1 week (acute) and 4 evaluated at 4 weeks (chronic). Treatment groups were acute bilateral (3 swine, 6 ablations with immediate computed tomography [CT] and sacrifice); chronic single kidney (3 swine, 3 ablations; CT at day 0, week 1, and week 4 after treatment, followed by sacrifice); and chronic bilateral (1 swine, 2 ablations). Treatments were performed using a prototype system (VortxRx; HistoSonics, Inc) and targeted a 2.5-cm-diameter sphere in the lower pole of each kidney, intentionally including the central collecting system. Results: Mean treatment time was 26.4 minutes. Ablations had a mean diameter of 2.4 +/- 0.3 cm, volume of 8.5 +/- 2.4 cm(3), and sphericity index of 1.00. Median ablation volume decreased by 96.1% over 4 weeks. Histology demonstrated complete lysis with residual blood products inside the ablation zone. Temporary collecting system obstruction by thrombus was observed in 4/11 kidneys (2 acute and 2 chronic) and resolved by 1 week. There were no urinary leaks, main vessel thromboses, or adjacent organ injuries on imaging or necropsy. Conclusions: In this normal porcine model, renal RAST demonstrated complete histologic destruction of the target renal tissue while sparing the urothelium.