Numerical simulation for prediction of thermal history in cryoprobe assisted biological tissue freezing

Cryosurgery is fast gaining popularity as a minimally invasive surgery for treatment of various types of cancers. It involves destruction of cancer cells within a limited spatial domain by exposing them to very low temperatures while minimizing injury to the surrounding healthy tissues. The volumetric extent of the critical isotherm in the ice ball decides the efficacy of the cryosurgical process. The thermal history within the ice ball during the freezing process remains an unknown and possesses a major challenge in any cryosurgical process. Numerical simulations prove to be very useful in this regard.

This paper presents an Enthalpy based numerical solution for phase change heat transfer in biological tissue cryo-freezing process using the Bio-heat transfer equation. The tissues are treated as non-ideal materials which freeze over a finite temperature range. The effects of blood perfusion and metabolic heat generation in the unfrozen tissues are also taken into account in the heat transfer model. This paper also discusses in brief the cell destruction mechanisms. Analytical solution for one dimensional water freezing was used for benchmarking the numerical model. Primary findings of these numerical investigations would prove to be useful in deciding the cryosurgical protocol and in the design and development of cryoprobes for future medical applications.