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 sta ndardized cryo-iceball using a porcine kidney model in order to establish t he threshold temperature for tissue ablation. To evaluate the ability to pr edict 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 calcu lated using a thermal finite element model. The threshold temperature for t issue injury was established by directly correlating end temperature and hi stologic 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 tempe rature of -16.1 degreesC 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 mag become a powerful tool in cryosurgery, improving the as sessment of damage in normal and malignant tissue.