[Radiation injury of the normal brain tissue after external radiotherapy of brain tumor].

The calculated dose expressed by neuNSD (or neuret) shows a significant relationship between a therapeutic dose and a post-radiation time in the normal brain injury. An aged patient and a patient with the vulnerable brain in the irradiated field had the high risk of radiation injury. Radiotherapy needs to consider the cost-benefit balance for those risk patients. The hyalinization of the vessels and demyelination were observed even in low-dose radiation areas in non-aged patients, and in aged patients fibrinoid necrosis was observed in low-dose radiation areas. The combination of intraarterial chemotherapy and radiotherapy increased the injury of the brain. If the low-density area existed within the irradiated field on CT, it could be a cause of radiation injury. Steroid and anticoagulant drugs should be given to recover from the condition before radionecrosis.