NUMERICAL-SOLUTION OF THE MULTIDIMENSIONAL FREEZING PROBLEM DURING CRYOSURGERY

A multidimensional, finite difference numerical scheme for the freezin g process of biological tissues during cryosurgery is presented, which is a modification of an earlier numerical solution for inanimate mate rials. The tissues are treated as nonideal materials, freezing over a temperature range and possessing temperature-dependent thermophysical properties, blood perfusion, and metabolic heat generation, The numeri cal scheme is based on the application of an effective specific heat, substituting the intrinsic property, to include the latent heat effect within the phase transition temperature range, Results of the numeric al solution were verified against an existing exact solution of a one- dimensional inverse Stefan problem in Cartesian coordinates, Results w ere further validated against experimental data available from the lit erature. The utility of the numerical solution for the design and appl ication of cryodevices is demonstrated by parametric studies of the fr eezing processes around spherical and cylindrical cryoprobes. The para meters studied are the cryoprobe cooling power and the dimensions of t he frozen region. Results are calculated for typical thermophysical pr operties of soft biological tissues, for angioma and for water.