Gamma knife is now widely used in the treatment of residual and recurrent glioma, and satisfactory results have been achieved in the treatment of intracranial metastases. Relative to benign tumors small doses can achieve satisfactory tumor control rate, in the treatment of malignant tumors, a single large dose of radiation therapy may lead to serious radiation reactions, in order to reduce radiation reactions, and may lead to a shortage of effective treatment dose and affect the efficacy. For large tumors, craniotomy is preferred, and for tumors in deep brain and functional areas, surgery has high disability and mortality rates. For this reason, we combined the theory of conventional radiotherapy dose fractionation with the characteristics of gamma knife high-dose simple irradiation of tumors, and used the gamma knife dose fractionation treatment method to treat gliomas and metastases in deep brain and functional areas from May 2005 to March 2006. 16 cases of metastatic tumors. General data and methods 1. Clinical data: 16 cases of malignant tumors, 9 males and 7 females, aged 41-70 years old, average 55 years old, were treated with gamma knife dose-splitting fractionation from May 2005 to March 2006. All cases were diagnosed by clinical manifestations and imaging data, including 10 cases of glioma, 1 case of recurrence after surgery, pathology of glioma grade II-III, 6 cases of metastases, 2 cases with a history of lung cancer surgery, 1 case of adenocarcinoma of the lung, and 1 case of small cell carcinoma of the lung. One case of glioma recurrence had a history of radiotherapy before gamma knife treatment. Glioma imaging classification: 2 cases of low-grade malignant glioma and 8 cases of highly malignant glioma. Metastatic tumor single lesion in 3 cases, 2 cases with 2 lesions, and 1 case with 3 lesions. Clinical manifestations: headache and dizziness in 7 cases, numbness and weakness of limbs in 12 cases, dizziness, unstable walking in 1 case, choking and coughing in 2 cases, and convulsions in 1 case. Tumor sites, basal ganglia area in 4 cases, parietal ventricle in 3 cases, thalamus in 3 cases, pontine brain in 2 cases, medulla oblongata in 1 case, parietal lobe in 3 cases, temporal lobe in 4 cases. The tumor volumes ranged from 4.5 to 105 cm3, with an average of 48.97 cm3. 2. Methods: The treatment planning was performed by using the OUR-GDX rotary gamma knife with a positioning head frame and r-TRS after MRI scanning and positioning. According to the size and location of the tumor, the number of divisions was 2-5, with a median of 3. The dose of each division was 2-8 Gy, with a mean of 5.45 Gy. The isodose curve was 30%-50%, and the median isodose curve was 45%. Different segmentation methods were used according to the condition and patient tolerance. (3 times/2 days) in 5 cases, (2 times/1-2 days) in 7 cases, no removal of the positioning head frame during treatment, (2 times/day) repositioning at one week interval (2 times/day) in 3 cases. One case of medullary tumor was treated twice in one day, repositioned one week later for two more treatments in one day, and repositioned two weeks later for one additional treatment. The interval between the two treatments was at least 8 hours, and 250 ml of mannitol plus 10 mg of dexamethasone was administered two to three times daily during treatment to reduce the cerebral edema response. The follow-up rate was 94.8%, with 15 cases of 16 patients followed up by clinic visits and telephone calls and 1 case lost. The follow-up period was 3-10 months, with an average of 6 months. 1 case died 3 months after treatment due to exacerbation of the disease. There were 6 cases of complete remission of clinical symptoms, 7 cases of improvement, and 2 cases of exacerbation, with a remission rate of 86.7%. 14 cases were followed up with imaging at 1-6 months, with 3 cases of disappearance, 8 cases of shrinkage, 2 cases of no change, and 1 case of enlargement of the lesion. There were 2 cases with worsening clinical symptoms, 1 of which was a death case, and 1 case with enlarged tumor on imaging review. The tumor disappeared on imaging review in 2 cases as metastases. 1 case of occupancy in the basal ganglia area (glioma, lymphoma possible), and the tumor basically disappeared after 1 month, which tended to be considered lymphoma by the efficacy of treatment. 4 cases with symptomatic remission or improvement were aggravated after 2-3 months, 2 cases were suggested to be recurrence on imaging review, and 2 cases were suggested to have tumor shrinkage on MRI review in the 1st month and 2nd month after treatment, but in 2 In two cases, although the tumor shrunk on MRI at month 1 and month 2 after treatment, the symptoms worsened again 2 months later due to severe cerebral edema reaction. Discussion Gamma knife dose fractionation therapy is firstly based on the theory that tumor cells are in different proliferation cycles. Tumor cells in M phase (mitotic phase) and S phase (DNA synthesis phase) are sensitive to radiation, while G1 and G2 phases are relatively insensitive, as well as the presence of G0 phase (dormant phase) cells. After one treatment, the cell cycle is redistributed and the surviving cells enter the sensitive phase and are treated again, improving the inactivation rate of tumor cells. Meanwhile, the reoxygenation of depleted cells in the tumor center and necrotic area in the inter-irradiation period. It also increases the killing rate of tumor cells. And the repair ability of late responding normal tissues to radiation damage is higher than that of tumor cells, and the high-dose focused irradiation of gamma knife increases the killing ability of tumor on the one hand, and reduces the damage of surrounding normal brain tissues at the same time. Studies by domestic and foreign scholars have shown that gamma knife dose fractionation treatment significantly improves the efficacy.