Gamma Knife is a special modality of radiation therapy, which is a special case of precision radiotherapy. The rays are gathered in narrow beams from multiple angles and in different directions towards the target area of treatment. The multiple beams all intersect at one point, creating a kind of focal treatment. This allows for a high local dose at the focal point and a low dose around the focal point, which helps to protect the normal tissue around the lesion. The beam of the gamma knife is limited by a circular beam limiter that restricts the field size to 3 cm. Therefore, it is only suitable for the treatment of circular lesions not exceeding 3 cm. Anomalous lesions, which are more than 3cm in diameter, are not suitable. And most of the malignant tumors are irregularly growing, and there are few spherical lesions. Therefore, most malignant tumors are not suitable for radiotherapy with Gamma Knife. Gamma knife is suitable for many benign diseases, such as: functional neurological diseases, including intractable pain, Parkinson’s disease, epilepsy, primary trigeminal neuralgia, etc. Cerebrovascular diseases: intracranial arteriovenous malformations, intracranial arteriovenous tumors, cavernous hemangiomas, etc. Benign tumors: such as auditory neuroma, meningioma, pituitary adenoma, pineal area tumor, craniopharyngioma, etc. Gamma knife is used for malignant tumor treatment: smaller similar round spherical lesions. Some malignant tumors after radiation treatment, the need to make up the amount of residual lesions that resemble a circle, the gamma knife can be used as a tool to reduce the field to make up the amount. For example, nasopharyngeal carcinoma, some intracranial malignant tumors after radiotherapy or after surgery, etc. It is mostly not applicable for other malignant tumors. Because of the odd shape of the tumor, it is more suitable to use conformal radiotherapy technique.