On the study of the freeze–thaw thermal process of a biological system

The key objective of cryosurgery is to kill cells within a closely defined malignant region. To effectively kill cells within the biological tissue, it is important to control the cooling/thawing rate over some critical range of temperatures and freezing states in order to regulate the spatial extent of injury during freezing. The present paper has developed a model to study the freeze–thaw thermal process of a biological system. A thermal simulation algorithm has been employed to generate transient temperature profiles, to visualise isotherms in the anatomical region of interest and to provide essential information for estimating the amount of freezing damage to the targeted biological tissue. Calculations may be made for any given freezing/thawing period and desired set of operating parameters. Extensive validation of the proposed model has been performed by comparing with experimental results obtained from an experimental setup as well as data from literature. Transient temperature profiles and freezing-front positions were compared between model and experiments. Validating with in vitro data from freezing porcine liver samples, the model demonstrated good agreement of up to 6.8%. The effects of implementing different freeze–thaw cycle schemes on the ice-ball development and temperature profiles within the biological tissue were quantitatively investigated. In addition, connecting the model with cell survival signature, the degree of cellular injury within the biological tissue was studied.