Numerical Study and Experimental Verification of Tissue Cryofreezing Based on Flexible Cryoprobe System.

Cryosurgery is effectively used for treating various diseases including cancer and tumor. But there is difficulty accurately quantifying the spatial temperature profile needed to determine diseased tissue destruction.A novel flexible cryosurgical probe was developed that can pass through the natural cavities of human body to minimize the damage to normal tissues. The present study aims to study the design of the flexible cryoprobe by 3D heat transfer modeling and experimental verification.A 3D model, on the basis of the flexible cryoprobe system, was developed to predict the temperature distribution during cryosurgery in porcine liver. In vitro experiments and pathological analysis with TUNEL staining of tissue samples were performed for verification.The results of numerical simulation based on the Pennes equation exhibited good agreement with experimental measurements for the flexible cryoprobe system. The simulation shows that the tissue within the range of 0 to 6 mm along the cryoprobe is effectively destroyed and the temperature in this domain decreases to the range -35°C to -40°C. Due to the non-uniform distribution, the temperature in the z-axis direction decreases to -40°C faster, with more serious tissue damage; whereas the x-axis direction has the greater distance of tissue destruction. Pathologic analysis of tissue after in vitro cryosurgery has verified the efficacy of the flexible cryoprobe system.Numerical simulation and experimental verification demonstrate the efficacy of the flexible cryoprobe system. The 3D heat transfer model can be a valuable tool for optimizing the design of the flexible cryoprobe system.