Evaluation and analysis of radiation exposure to normal tissues during gamma knife radiosurgery for vestibular schwannoma

Background: a follow-up study of gamma knife radiosurgery has shown that postoperative radiation necrosis, radiation-induced edema, and malignant metastasis may occur. this may be due to secondary radiation exposure, therefore, it becomes necessary to actively reduce exposure to normal organs. materials and methods: in this study, the secondary radiation dose to the surrounding normal organs was measured during gamma-knife radiosurgery for vestibular schwannoma disease. using a human pediatric phantom and a glass dosimeter, a treatment plan was established according to the tumor volume, and then the exposure dose to important normal organs in both eyes, thyroid gland, sternum, and both lungs was measured. results: according to this study, the cancer occurrence probability due to secondary exposure was calculated to be 7 cases per 100,000 people up to the case of the eye and thyroid gland. exposure doses of 100.2±0.79 mgy or more were measured in both eyes, which is approximately 1000 times that of a chest x-ray or a flight from seoul to new york. this indicates exposure through gamma knife surgery. the dose to the thyroid gland was 12.7±0.05 mgy, which exceeds the effective dose of 10 msv in abdominal computed tomography. conclusion: by measuring the secondary exposure dose to normal organs during gamma-knife surgery for vestibular schwannoma disease, it was confirmed that the eyes and thyroid gland were exposed dangerously. therefore, for pediatric patients specifically, a treatment plan that actively reduces secondary exposure is required.