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

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.

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.

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.

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.