Finite Element Simulation of Multi-probe Cryosurgery with a Urethral Warmer

From a clinical point of view, it is very important to control the ice ball growth in view of sparing healthy tissues or vital structures such as the urethral lining, as well as to increase cryoinjury as much as possible to cancerous tissues. This paper is concerned with the thermal analysis of the freezing of a prostate using a multi-cryoprobe system including a urethral warmer. We address the effect of a urethral warmer (heat source) in combination with cryoprobes (heat sinks) in order to determine more realistically the actual temperature field in the prostate during cryosurgery. To improve the killing effects (mainly due to solution injury), the concept of dynamic cryosurgery in terms of both spatial and temporal thermal waves is examined. The evolutions of the temperature distribution, iceball size, shape, and location with respect to the urethral warmer and the cryoprobes are quantitatively illustrated by plotting contours of key governing field variables, e.g. freezing exposure index, and cooling rate. It is hoped that the present work will give valuable information and guidance to cryosurgeons before carrying out an operation in similar cases.