Numerical Simulation of Cryosurgery as a Potential Treatment for Uterine Fibroids

Nearly 80% of all women may suffer from menorrhagia caused by uterine fibroids (leiomyomas) which are benign tumors made up of muscle and fibrous tissue that grow from the muscular wall of the uterus. The vast majority of women whose symptoms are strong enough to require treatment obtain a hysterectomy. Other treatment options which are less invasive than hysterectomy include thermal therapies such as thermal ablation or cryosurgical removal of tissue. This project numerically evaluates the efficacy of a liquid-nitrogen-based cryotherapy for the treatment of uterine fibroids. A bioheat transfer model was utilized which includes both the effects of blood perfusion and the impacts of liquid-to-solid phase change. Changes in all physical properties including thermal conductivity, heat capacity, and perfusion rate were taken into account as the tissue passed through a range of temperatures where it would be transitioning from unfrozen to fully frozen. The numerical model was based on a one-dimensional unsteady bioheat equation. The results show that even for the direct-contact cooling, it is unlikely that intracellular ice would form during the procedure. On the other hand, based on data obtained from previous cell-survival studies, it was found that necrosis would occur when the cooling rates exceeded 30°/min. According to the present numerical results, necrosis would occur within the tissue up to a depth of approximately 5.8 mm, thereby ensuring that sufficient tissue would be cryosurgically destroyed to result in effective treatment.