Radiation therapy instruments The purpose of radiation therapy is to use radioactivity to kill tumor cells so that the tumor can be controlled. There is a long history of using radiation to treat malignant tumors. Conventional radiotherapy is now widely used. Many years of research and clinical practice have confirmed that the dose of Υ-rays and X-rays decays exponentially with depth after entering the human body, and most of the dose is lost in the skin and normal tissues in front of the tumor. This poses a great difficulty for treatment, on the one hand, to ensure that tumor tissues receive sufficient lethal dose, and on the other hand, to prevent normal tissues from receiving too much irradiation dose and causing damage. The traditional conventional radiotherapy is to use multiple segmentation irradiation method to kill the tumor cells through the accumulation of doses, taking advantage of the fact that normal tissues can be easily repaired after irradiation, while tumor tissues are not easily regenerated. Over the past half century, conventional radiotherapy equipment has made a lot of improvements in terms of energy, dose rate, irradiation field, beam current characteristics and radiation protection, and the treatment methods and levels have also made substantial progress, but in general, the expected therapeutic effects have not been achieved. It is recognized that conventional radiotherapy lacks precise stereotactic means, and it is difficult to ensure the maximum killing of tumor tissues while avoiding damage to healthy tissues by adopting fixed path or merely isocentric irradiation methods. In 1951, Professor Leksell, a famous Swedish neurosurgeon, firstly proposed the stereotactic radiotherapy method, in which the radiation is directed to the lesion from different directions to create a high-dose focusing effect in the center of the lesion while reducing the damage to healthy tissues, thus causing necrosis of the lesion and achieving the effect of surgical removal of the tumor. Professor Reichel’s stereotactic radiotherapy approach has become a classic in stereotactic radiosurgery, with two distinctive technical features: (1) precise stereotactic means; and (2) multi-path irradiation to create a great focal ratio (the ratio of dose per unit volume of diseased tissue to healthy tissue) that far exceeds that of conventional radiotherapy. From the perspective of clinical radiation dosimetry, the stereotactic radiation therapy method achieves accurate and uniform dose irradiation to tumor tissues, which ensures maximum killing of tumor tissues while greatly reducing the damage to healthy tissues. In this way, it brings revolutionary changes to radiation therapy methods. Through the computerized treatment planning system, it is possible to apply high doses of lethal irradiation to tumor tissues at one time and remove tumors like surgery. It is called “radiation scalpel”. After decades of efforts, with the development of modern medical image diagnostic devices and computer technology, from the 1970s stereotactic radiosurgery technology began to be used in clinical practice, and continue to develop, forming static, dynamic rotary scanning and arc center three categories of stereotactic methods, and the formation of static gamma knife for the treatment of brain tumors, rotary gamma knife and head X knife three series of ray scalpel products. The ray scalpel has achieved recognized therapeutic effects and cured tens of thousands of brain tumor patients. As long as the treatment protocols are strictly followed, it has been proven that the radiation scalpel is a safe and effective radiation therapy with minimal side effects.