A thermal-ablation bioheat model including liquid-to-vapor phase change, pressure- and necrosis-dependent perfusion, and moisture-dependent properties

A new bioheat model is applied to evaluate the use of elevated-temperature thermal therapies for the non-surgical ablation of diseased tissue. The new model is based on the use of the enthalpy method to account for liquid-to-vapor phase change. In addition, the model includes thermophysical property dependence on liquid content and variations of blood perfusion rates dependent on the local necrotic state of the tissue or external pressure applied by the therapy-delivering device. This model is applied here specifically to endometrial ablation for the treatment of menorrhagia. The results of the implementation of the model yielded the depth of tissue necrosis corresponding to a given application of heat at the exposed inner surface of the uterine tissue. These results definitively establish the occurrence of phase change and the complete suppression of perfusion as the major factors governing the necrosis depth. The accounting of moisture-dependent properties had a negligible effect on necrosis.