Numerical simulation of 3-D freezing and heating problems for combined cryosurgery and hyperthermia therapy

Recently, a new tumor ablation modality based on freezing immediately followed by a rapid and strong enough heating has been proved to be more effective and flexible than conventional cryosurgery. In this study, a numerical algorithm based on the effective heat capacity method is established to solve three-dimensional (3-D) phase-change problems of biological tissues subject to combined freezing and heating. The accuracy of the numerical code thus compiled is validated through comparisons of the calculation results with a 1-D exact solution for a semi-infinite region solidification problem. Using the present algorithm, comprehensive analysis is performed on the freezing/thawing behavior of biological tissues with tumors. For treatment of large tumors, where strong cooling/heating power is required, a single probe will not be able to address a sufficiently large volume. For this case, freezing/heating problems using a three-probe system are solved for illustration purposes. The present algorithm is expected to be a valuable treatment-planning tool for combined cryosurgery and hyperthermia therapy.