Overview of Radiation Oncology Radiation oncology is an independent discipline that combines multidisciplinary and high-tech technologies. About 70% of tumor patients need to receive radiation therapy to varying degrees in order to cure their tumors or relieve their symptoms and improve their quality of life. At present, the five-year cure rate of nasopharyngeal cancer, laryngeal cancer, rectal cancer and other early-stage or stage Ⅰ tumors can reach more than 80-95% after simple radiotherapy, and the five-year survival rate of nasopharyngeal cancer, cervical cancer, Hodgkin’s lymphoma, prostate cancer, etc. can reach 40-50% in all stages. Radiotherapy combined with surgery, chemotherapy and other therapies can make 40% of all kinds of cancers clinically cured. The relief rate of radiotherapy for intractable pain caused by bone metastases of malignant tumors can reach 80-90%, and it can achieve the purpose of local control of tumors to different degrees. In recent years, as the theory and viewpoint of comprehensive treatment of tumors are recognized and clinically implemented, as well as the development and improvement of radiotherapy equipments and techniques, especially the clinical application of conformal intensity-modulated three-dimensional radiotherapy technology, it expands the range of radiotherapy indications and improves the therapeutic efficacy of radiotherapy for tumors. The fact that radiotherapy has become one of the important and effective means to treat and control tumors has been widely recognized. Radiation oncology, like all other disciplines, is still developing and improving, and will continue to make great contributions to the defense of human health for a long time to come. What are the advantages of radiation therapy? Radiation therapy is one of the three major clinical tumor treatments (surgery, radiotherapy and chemotherapy). Its advantages are as follows: 1. Wide scope of application, can treat almost any tumor in all parts of the body. 2. 2. It does not require high requirements for the patients to receive treatment. Patients who cannot tolerate other therapies due to old age, poor physique, multiple surgeries, etc. can receive radiotherapy. 3.The treatment effect is real and the treatment method is reliable. 4, the treatment process is simple, painless, does not necessarily require hospitalization, easy to be accepted by patients. 5, treatment side effects are very few, can avoid anesthesia accident caused by surgery, blood transfusion reaction, postoperative infection, and chemotherapy caused by hair loss, vomiting and other side effects. 6. Radiation therapy is non-traumatic and can preserve the physiological functions of the diseased organs. The goal pursued by tumor radiotherapy technology The ability to maximize the radiation dose concentrated to the lesion (target area), killing tumor cells, while making the surrounding normal tissues and organs less or free from unnecessary irradiation, so as to be protected, this is the goal pursued by tumor radiotherapy. Technical classification of radiotherapy: I. Conventional radiotherapy: Conventional radiotherapy technology features: 1. Irregularly shaped irradiation field in two-dimensional direction obtained by regular shape or shielding with lead mold. 2. 2, the dose distribution of each point in the irradiation field is relatively uniform. Advantages: the requirements of equipment and technical conditions are low, the operation is relatively simple, and it is mostly used for preoperative and postoperative radiotherapy of malignant tumors. Disadvantages: the shape of irradiation field and the shape of tumor in three-dimensional direction are not completely consistent, and more normal tissues are included in the irradiation field, which is not suitable for cases where there are sensitive tissues and vital organs around the tumor. Precision radiotherapy (taking intensity-modulated conformal radiotherapy as an example) Features of precision radiotherapy: 1. What is conformal? From the three-dimensional direction, multiple irradiation fields and angles are used to irradiate, and the cross-section shape of each field is consistent with the corresponding tumor cross-section shape. 2. What is intensity adjustment? According to the tumor condition, using CT scanning, the reverse 3D treatment planning system designs a reasonable and changing dose distribution to make the tumor surface and internal points receive uniform dose. Advantages: It can increase the irradiation dose to the tumor and kill the tumor cells more effectively, and it can also achieve the purpose of protecting normal tissues and organs more effectively, improving the therapeutic effect, improving the quality of life, and expanding the scope of radiotherapy indications. Disadvantages: It is necessary to use spiral CT scanning three-dimensional imaging, simulation positioning system and reverse three-dimensional treatment planning system, which is more expensive and technically complex.