Radiotherapy modalities can be divided into the following according to different irradiation methods: 1.Distant external irradiation: referred to as external irradiation, the radiation source is located in the machine outside the human body, and the radiation is focused on the patient’s tumor site through the equipment; 2.Intra-tissue irradiation: referred to as close irradiation, the radiation source is sealed and put into the human tissue or the natural cavity of the human body, such as nasopharyngeal cavity, esophagus, cervix, etc. Different radiation methods are chosen according to the patient’s condition. Currently, most of the treatment is external irradiation, and some tumors, such as cervical cancer and esophageal cancer, will be appropriately combined with the use of brachytherapy.