Gamma knife is actually not a knife, but a form of radiotherapy. Gamma refers to gamma rays, the current application of radiotherapy gamma rays are generated by cobalt-60 radionuclide; the reason why it is called “knife” is because in the treatment can form a very high dose of radiation in the tumor site, and in the tumor around the radiation dose drops steeply, forming a “knife The reason why it is called “knife” is that it can create a very high radiation dose at the tumor site during the treatment, while the radiation dose around the tumor drops steeply, creating a “knife” like radiation effect. We can use a hypothesis to understand this problem, suppose a tumor grows in a certain part of the body, the tumor must be surrounded by normal tissue, if we heat the tumor site to 200 degrees, while the normal near the tumor is 5 degrees, so as to achieve to kill the tumor and normal tissue is not damaged. Gamma knife was first proposed by a doctor in Sweden and developed successfully, at first mainly used to treat intracranial tumors, now generally known as the head gamma knife (referred to as “head knife”), and later some domestic researchers on this basis developed the body gamma knife (referred to as the body knife), used to treat tumors other than intracranial tumors. In clinical practice, Gamma Knife has played a very good therapeutic role in some lesions to achieve the same effect as surgery, but all methods of disease treatment have indications and contraindications, if abused will not achieve the desired effect of treatment, Gamma Knife is also the case. At present, the domestic application of gamma knife is relatively chaotic, bringing confusion to patients. Some tumor patients blindly believe in Gamma Knife, but do not know whether it is suitable for Gamma Knife treatment, we look at the indications for Gamma Knife treatment of malignant tumors that is, when to apply Gamma Knife treatment. 1, the size of the tumor, gamma knife is suitable for less than 3cm tumor treatment, if you relax some tumor size should not exceed 5cm. why the size of the tumor has this strict limit? Because the tumor is small in order to reach the “knife” treatment results, such as tumors more than 5cm will not reach the “knife” effect, the damage to normal tissue with ordinary radiotherapy is the same, lost the meaning of gamma knife treatment (involving some radiation therapy dosimetry and At the same time, the cost of ordinary radiotherapy and gamma knife treatment is not the same, the cost of gamma knife treatment is much higher than ordinary radiotherapy. 2, must be used visible tumor lesions, if the tumor patient first underwent surgery, and the removal is very clean, postoperative CT, MRI review did not see the tumor or metastatic lymph nodes, and the patient needs radiotherapy, then you can not choose gamma knife, to choose ordinary radiotherapy or conformal intensity modulated radiotherapy. 3.It is suitable for single lesion or tumor with no more than 3-5 lesions, not for those with lymph node metastasis. If lymph node metastasis is found through CT examination, then there may be small metastatic lymph nodes that cannot be seen by CT. The application of Gamma Knife treatment alone will miss these lymph nodes, so general-pass radiotherapy should be used. 4, for patients who refuse surgery or patients who are not suitable for surgery, the above principles should also be followed. It should be noted that: the same site of radiotherapy can generally be carried out only one course of treatment in a lifetime, whether it is gamma knife or general radiotherapy and conformal intensity modulated radiotherapy. So be sure to consult with your radiologist before radiation therapy to find out exactly what type of radiation therapy is better.