Calibration of a Novel, Laparoscopic, 12-mm, Ultrasound, Image-guided, High-intensity Focused Ultrasound Probe for Ablation of Renal Neoplasms

Objective To calibrate a 12-mm high-intensity focused ultrasound (HIFU) probe to produce histologically verifiable complete tissue necrosis through thermal energy delivery while maintaining safety in ablation of porcine renal tissue. Methods The study was approved by the animal research committee at our institution. A HIFU probe on a fixed arm was introduced, and ablation was subsequently carried out robotically (under computer control) at 2 planned locations within each kidney at varying energy levels. After 4 days of survival, kidneys were retrieved and pathologic analysis of the lesions was carried out for necrotic volume. Planned volume was compared with pathologic necrotic volume. Results A series of optimizations were carried out as the experiment progressed. Near optimal ablation zone dimensions with complete cell death were achieved when the energy density was between 400 and 460 calories/cm 3 . Pathologic analysis demonstrated the average ratio of necrotic zone volume to planned zone volume was 1.0 (standard deviation, 0.18) in the 7 lesions with energy density between 400 and 460 calories/cm 3 . All animals survived the surgeries, and no device-related complications were identified during the study. No acute renal failure was identified in analysis of the blood work. Conclusion A novel 12-mm laparoscopic HIFU probe was successfully calibrated for the ablation of porcine renal tissue. The safety profile of the Sonatherm probe was found to be excellent with no complications identified.