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.