Regulating the cryo-freezing region of biological tissue with a controlled thermal device

Cryoablation is a minimally invasive technique that kills tissue in situ through freezing and is used to destroy unresectable benign and malignant tumors. A key objective of this therapeutic technique is to kill cells within a closely defined malignant region while inflicting minimal thermal injury to the surrounding healthy tissue. The extremely low temperatures used in cryoablation inevitably cause varying degrees of damage to the surrounding healthy tissue. Thus, we proposed a simple, effective, and non-invasive heating device that can be easily incorporated into the existing cryosurgical technology. The chief aim of this device is to reduce the over-freezing of neighboring healthy tissue. A model was developed to study the performance of the proposed device during cryo-freezing of a biological tissue, for example porcine liver. The model, validated with the in vitro experimental data, demonstrated good agreement of up to 6.3%. The performance of the proposed device was evaluated using a dimensionless parameter termed the heating coil coefficient. Results demonstrated that the implementation of a heating coil is instrumental for reducing the size of undesired boundary lesions. The adoption of a 50-mm-diameter heating coil reduced the freezing of neighboring tissue by up to 56% within a freezing time of 10 min. This study establishes a framework for the selection of a correctly sized heating device to reduce the over-freezing of neighboring healthy tissue optimally.