Measurement and prediction of thermal behavior and acute assessment of injury in a pig model of renal cryosurgery.

PURPOSE To analyze in vivo end temperatures and histologic injury in a standardized cryo-iceball using a porcine kidney model in order to establish the threshold temperature for tissue ablation. To evaluate the ability to predict end temperatures using a thermal finite element model. MATERIALS AND METHODS A single freeze/thaw cryolesion was created in five pig kidneys and the temperature history recorded. End temperature was calculated using a thermal finite element model. The threshold temperature for tissue injury was established by directly correlating end temperature and histologic injury. RESULTS Reproducible geometry and temperature profiles of the cryo-iceball were found. End temperature could be accurately predicted through thermal modeling, and correlation with histologic injury revealed a threshold temperature of -16.1 degrees C for complete tissue ablation. CONCLUSION Thermal modeling may accurately predict end temperature within a cryo-iceball. Provided threshold temperatures for tissue destruction are known, modeling may become a powerful tool in cryosurgery, improving the assessment of damage in normal and malignant tissue.