Radiotherapy, or radiation therapy, consists of five parts: positioning, CT simulation scanning, planning, validation of the plan, and initiation of radiotherapy. 1. Positioning: The patient is positioned before radiotherapy using a body fixation method to assist in positioning, through the use of auxiliary fixation devices, such as some head, face and neck tumors and thyroid tumors, the use of body molding methods to assist: the patient is fixed to the bedpan, in order to expect to reduce the wobbling of the radiotherapy, and other auxiliary methods also include the body racks, vacuum pads and so on, which can assist in the fixation of the patient. 2. CT simulation scanning: Immediately after positioning the patient, a simulation scan is performed to scan and examine the lesion and the surrounding areas of the lesion, and then the target area is ticked off after completion. The clinician clarifies the extent of tumor invasion and the range of normal organs that need to be protected through the simulated images formed. 3. Formulation of plan: After determining the radiotherapy site, the clinician will submit the target area drawing to the radiotherapist, who will choose the treatment plan according to the radiotherapy range outlined by the clinician, try to increase the radiation dose to the tumor site and reduce the radiation dose to the surrounding normal parts, so as to treat the tumor without harming normal tissues. 4. Validation of the plan: In the clinic, the doctor will validate the treatment plan according to the chosen treatment plan and judge whether the treatment plan is consistent with the treatment requirements. 5. Start radiotherapy: After the above process, the patient can enter the daily routine treatment.