A semi-empirical treatment planning model for optimization of multiprobe cryosurgery

A model is presented for treatment planning of multiprobe cryosurgery. In t his model a thermal simulation algorithm is used to generate temperature di stribution from cryoprobes, visualize isotherms in the anatomical region of interest (ROI) and provide tools to assist estimation of the amount of fre ezing damage to the target and surrounding normal structures. Calculations may be performed for any given freezing time for the selected set of operat ion parameters. The thermal simulation is based on solving the transient he at conduction equation using finite element methods for a multiprobe geomet ry. As an example, a semi-empirical optimization of 2D placement of six cry oprobes and their thermal protocol for the first freeze cycle is presented. The effectiveness of the optimized treatment protocol was estimated by gen erating temperature-volume histograms and calculating the objective functio n for the anatomy of interest. Two phantom experiments were performed to ve rify isotherm locations predicted by calculations. A comparison of the pred icted 0 degrees C isotherm with the actual iceball boundary imaged by x-ray CT demonstrated a spatial agreement within +/-2 mm.