1, what is radiation? In a night in December 1895, Germany, a world-famous physicist Röntgen (ROentgen 1845 ~ 1923) in the physics laboratory for the study of cathode rays characteristics of the test found that: the discharge of glass tubes not only emit visible light, but also emit some kind of invisible rays, which are very penetrating rays that can penetrate the glass, boards, and muscles, etc., and can also penetrate the Black paper so that the film wrapped in light-sensitive, but also can make the cardboard coated with barium cyanate flashes light green fluorescence, but it is difficult to penetrate the bone. Röntgen also used this ray to take photographs of his wife’s hand bones. He thought that the newly discovered ray nature is very mysterious, can only be counted as an unknown, so the math in the number of “X” borrowed, called “X-rays”. Later, after many years of research by scientists, only to recognize the essence of “X-rays”, in essence, it is a photon stream, an electromagnetic wave, with the characteristics of light, is a member of the family of spectra, only its oscillation frequency is high, the short wavelength is just, its wavelength in the 1 ~ 0, 01 Å (1 Å = 10-10 meters). X-rays in the spectrum of the highest energy, the widest range, from ultraviolet until dozens or even hundreds of megaelectronvolts (Mv) (M). hundreds of megaelectronvolts (MeV). Because of their high energy, they can penetrate a certain thickness of material. The higher the energy, the thicker the penetration, so it can be used in medicine for fluoroscopy, photographs and radiation therapy. In the course of radiation research, scientists have also discovered that radioisotopes can emit three types of rays when they decay: α, β, γ rays. α ray is essentially the helium nucleus flow, its ionization ability is strong, but weak penetration, a thin sheet of paper can be blocked; β ray is essentially the electron flow, ionization ability is weaker than α rays, and stronger penetration, it is commonly used in radiation therapy; γ rays are essentially the same as the X-rays, is a wavelength of a very short, high-energy electromagnetic waves, a photon flow, uncharged, and the same as X-rays, a photon flow. A photon stream, not charged, moving at the speed of light, with a strong penetrating power. Therefore, it is often used in radiation therapy. 2.What is radiation therapy? Radiation therapy refers to the use of radioisotope rays, ordinary X-rays produced by X-ray therapy machines, high-energy X-rays produced by gas pedals, as well as electron beams produced by various gas pedals, protons, fast neutrons, negative muons, and other heavy particles, etc., which are used to treat cancerous tumors. Radiation therapy in a broad sense includes both radiation therapy for tumors in the Department of Radiation Therapy and internal isotope therapy in the Department of Nuclear Medicine (e.g., 131 iodine for the treatment of thyroid cancer and hyperthyroidism, and 32 phosphorus for the treatment of carcinomatous pleural fluid, etc.). Radiation therapy in a narrow sense generally refers only to the former, i.e., what is commonly known as radiation therapy for tumors. Radiation therapy has two types of irradiation: one is long-distance radiotherapy (external irradiation), i.e. the radiation source is irradiated at a certain distance from the patient’s body, and the rays penetrate from the patient’s body surface to a certain depth in the body, so as to achieve the purpose of treating tumors, which is the most widely used and the most dominant; and the other is short-distance radiotherapy (internal irradiation), i.e. the radiation source is sealed and placed in or on the surface of the tumors, such as placed in the natural cavities or tissues (e.g. tongue, nose, nose). The other one is brachytherapy (internal irradiation), in which the radiation source is sealed and placed inside the tumor or on the surface of the tumor, such as into the natural cavity of the human body, or inside the tissues (such as the tongue, nose, pharynx, esophagus, trachea and the uterus and other parts of the human body), i.e., using the intracavity, inter-tissue insertion, and modeling, etc., to carry out treatment, which is an auxiliary means of the treatment of cancer by the remote 60-cobalt therapy machine or gas pedal. In recent years, with the continuous improvement of medical equipments in hospitals, brachytherapy has been popularized gradually. There are three basic differences between in vivo and ex vivo radiotherapy: ① compared with in vitro irradiation, in vivo irradiation, the intensity of the radiation source is smaller, from a few milli-curies to about 100 milli-curies, and the therapeutic distance is shorter; ② for in vitro irradiation, most of the energy of radiation is shielded by collimator, beam limiter, etc., and only a small portion of the energy reaches the tissues; in vivo irradiation is the opposite, and most of the energy is absorbed by the tissues; ③ for in vivo irradiation, the radiation ③In vitro irradiation, the radiation must pass through skin and normal tissue to reach the tumor, and the tumor dose is limited by the tolerance of skin and normal tissue. In order to get a high and uniform tumor dose, it is necessary to choose rays with different energies and adopt multi-field irradiation techniques, etc. In vivo irradiation, the rays will not reach the tumor tissues, and the irradiation of the deeper normal tissues will be very small. 3. Some people call radiation therapy as “baking electricity”, right? Some people call radiation therapy as “baking electricity”, which is an inaccurate term used by common people for radiation therapy. This is an inaccurate term used by the general public for radiation therapy. It may originate from the fact that radiation therapy causes the skin in the radiation field to redden and even turn “black” due to increased pigmentation, which is associated with similar skin changes caused by baking the skin with electric lamps or other electrical equipment. It is not known that the mechanism of action of the two is not the same. Radiation therapy is the use of radiation therapy equipment such as X-ray therapy machine, 60 cobalt therapy machine and gas pedal generated by the invisible, touchless, smelling rays (X-rays, & gamma; line and electron beams, etc.) to irradiate the tumor, so that the proliferation of the tumor cells of the deoxyribonucleic acid chain (DNA) damage, and then the loss of its ability to proliferate, resulting in cell death. Of course, radiation also damages normal tissues in the irradiation field, such as skin epithelium and epidermal capillary endothelial cells, which increases capillary permeability and exudes erythrocytes and inflammatory cells from blood vessels, resulting in inflammatory reactions; in addition, the increase in hyperpigmentation deepens the color of the local skin, which becomes red or even “black”. In this process, there is still the body’s own stabilization system plays a role, so that the skin epithelial damage repair, proliferation acceleration, repair and replacement of damaged epithelium. The use of electric lamps and other electrical equipment baking skin (“baking electricity”) is due to the local temperature rise, high heat caused by the skin surface capillary expansion, increased permeability, intravascular inflammatory cells and erythrocytes and other oozing, inflammatory response, so that the epidermis becomes red; of course, high temperatures will also be damage to the epidermal cells, damage to the endothelial cells in the capillaries to make it more permeable to increase the inflammatory response increased pigmentation and so on to make the skin red, even “black”. The skin becomes red, or even “black”, and finally the body repairs the damaged skin. Therefore, it is inaccurate to call radiation therapy as “baking electricity”. 4. Why can radiation treat tumors? People make use of the different effects and damages of radiation on normal cell groups and tumor cell groups of various tissues and organs, as well as the difference of their recovery ability, so that radiation therapy becomes one of the main means of treating tumors. Because after the normal tissues are damaged by rays, the automatic stability control system starts to work, the cell proliferation cycle is shortened, and the growth ratio of the cells is increased, so that the repair of damaged normal tissues is completed very quickly. On the other hand, the tumor cell population has its own, different reaction system from the normal tissue after being struck by rays, and the reaction is extremely different among different tumors. During the observation of human tumor cells, it is found that there is an obvious relationship between cell proliferation rate and cell loss and radiosensitivity, where the fastest average growth rate, high growth rate and cell renewal rate of tumors are more sensitive to radiation: general embryonic tumors are the most sensitive to radiation; lymphoid tumors are the second; epithelial tumors are again; and mesenchymal tumors are the least sensitive and need higher doses to play a role. The mesenchymal tumors are the least sensitive and require higher doses to be effective. Since normal tissues have automatic stability control system and tumor tissues are different, the recovery and growth of normal tissues and tumor tissues are different after irradiation: ① After irradiation, the cell proliferation cycle of normal tissues will return to normal quickly, while tumor tissues are slow in repairing the damage caused by radiation, and the cell proliferation cycle is prolonged; ② After irradiation, although the tumor may have a temporary accelerated growth phenomenon, the growth rate is still not as fast as the normal tissues to repair the damaged tissues. Although the tumor may have a temporary accelerated growth phenomenon after irradiation, the growth rate is not as fast as the proliferation of normal tissues for repairing the damage; ③ The growth rate of tumor cells is larger than that of normal tissues, and there are more cells in the cell cycle, so there are more lethal injuries than that of normal tissues, and the ones with different degrees of injuries are more than that of normal tissues. Therefore, in the clinical radiotherapy of tumor, the different radiotherapy effects of normal tissue and tumor tissue are used to carry out fractionated radiotherapy, so as to achieve the purpose of killing tumor cells and protecting normal tissue as much as possible. In the clinical treatment of tumor, more than 70% of tumor patients have received radiotherapy, including radical radiotherapy and palliative radiotherapy. 5. Does radiation damage normal tissues? In the process of clinical radiotherapy, radiation will inevitably have certain effects on normal tissues of human body, thus causing certain radiation reaction and damage. However, oncology radiotherapists firstly consider how to completely eliminate the tumor while avoiding and reducing the damage to normal tissues as much as possible, so as to achieve the purpose of curing the tumor, protecting the function, improving the quality of life and prolonging the life. Radiation damage to tissues and organs is related to many factors. The sensitivity of tissues to radiation (referring to the degree of damage) is directly proportional to their proliferative ability and inversely proportional to their differentiation degree, i.e., the stronger the proliferative ability the more sensitive the tissues are, and the lower the differentiation degree the more sensitive they are, and vice versa. For example, lymphatic tissue, bone marrow, testes, ovaries, small intestine epithelium, etc. are the most sensitive to radiation and are most easily damaged; followed by skin epithelium, cornea, oral and nasal cavity, crystals, stomach and bladder epithelium, etc.; the least sensitive tissues are muscle and nerve tissue. Under a certain irradiation dose, the larger the irradiated area, the greater the damage; the smaller the area, the smaller the damage. For a given irradiated area, the greater the rate of irradiation (single irradiation dose), the greater the damage. The degree of radiation response is affected by the general state of health as well as concomitant diseases, such as malaise, infectious diseases, and cardiopulmonary and vascular diseases. Age is also a factor, with adolescents being more sensitive than adults, but sensitivity increases again in old age. Radiation-induced normal tissue reactions are generally categorized into early primary reactions and late secondary reactions. Early radiation reaction generally refers to radiation-induced damage to the tissue cells themselves, as well as possible concomitant inflammation, such as acute radiation reaction of the oral and nasal mucosa causing localized mucosal redness, swelling, pain, shallow ulcers and pseudomembrane formation, etc.; acute dry or wet radiation reaction of the skin and so on. Late radiation reaction refers to radiation-induced occlusion of small blood vessels and coir tissue fibrosis and affect the function of tissues and organs, such as glandular hyposecretion caused by dry mouth, lungs, skin and subcutaneous tissue fibrosis contraction. The more serious radiation damage, such as radiological paraplegia, cerebral necrosis, osteonecrosis and intestinal necrosis, etc. are absolutely not allowed. 6.What are the advantages and disadvantages of treating tumor with radiation? As we all know, more than 70% of tumor patients have received different degrees of radiation therapy, what are the advantages and disadvantages of radiation therapy? (1) Advantages of radiotherapy: ① Many tumor patients can be cured and get long-term survival through radiotherapy, such as early nasopharyngeal cancer, lymphoma and skin cancer, etc.; ② The efficacy of radiotherapy is even as good as the efficacy of surgery for some patients, such as early cervical cancer, vocal cord cancer, skin cancer, tongue cancer, esophageal cancer and prostate cancer, etc., and the patients’ functions of speaking, pronouncing, mastication, eating and defecation are intact, and their appearances are preserved intact as well; After early breast cancer is treated by minor surgery and major radiotherapy, not only the survival time is the same as that of radical surgery, but also the appearance of the breast is preserved basically intact, which is accepted by female breast cancer patients in all countries in the world; ③ Some tumor patients cannot be treated surgically or have difficulty in resection at the beginning, but after preoperative radiotherapy, most of the patients’ tumors are shrunken, and the chances of tumor spreading are reduced in the operation, the resection rate is improved, and the survival rate is increased after the operation, for example, the middle- to late-stage cancers of the head and neck, the more However, after preoperative radiotherapy, most patients have their tumors shrunk, the chance of intraoperative tumor dissemination reduced, the resection rate increased, and the survival rate improved, such as middle and advanced head and neck cancer, more advanced esophageal cancer, breast cancer and rectal cancer, etc.; (4) Some patients need postoperative radiotherapy, which not only destroys the residual lesions but also improves the local control rate and the survival rate, such as lung cancer, esophageal cancer, rectal cancer, breast cancer, soft tissue sarcoma, head and neck cancer, and brain tumors, etc.; (5) For some other patients with poor physical condition, or with comorbidities that can not or are not willing to be operated, the effect of radiotherapy is also good. For those patients with advanced stage of disease or cancer caused by bone pain, dyspnea, increased intracranial pressure, broken superior vena cava and cancerous hemorrhage, radiotherapy can often reduce the symptoms and achieve the purpose of prolonging the life; (7) In recent years, due to the continuous improvement of radiotherapy equipments, the treatment planning system has been developed from two-dimensional to three-dimensional planning, such as the application of γ or X-knife, so that the tumors can be killed by a higher dose, and the amount of the surrounding normal tissues is greatly reduced. greatly reduced; the more precise irradiation of the tumor by conformal radiotherapy will certainly be welcomed by the majority of tumor patients in the near future. (2) Disadvantages of radiotherapy: (1) Radiation therapy equipment is expensive and the treatment cost is high; (2) Radiation therapy staffs are required to be comprehensive and skillful, including qualified radiotherapists, radiophysicists, radiobiologists, and skillful radiation technicians; (3) The cycle of radiation therapy is long, usually taking 1 to 2 months; (4) Radiation complications are more, even causing partial loss of function; (5) The effect of radiation therapy is not complete in some tumors, especially in the late stage tumors. ⑤ Some tumors, especially advanced tumors, are not well treated by radiation therapy. What kind of tumors can be treated by radiation therapy? Radiotherapy is one of the main treatments for malignant tumors and most patients need radiotherapy. Due to the different purposes of radiotherapy, it can be used as simple radical radiotherapy or palliative radiotherapy, or combined with surgery or chemotherapy. (1) Head and neck tumor: Radiotherapy is preferred for nasopharyngeal cancer and early vocal cord cancer; other tumors can be treated with combined treatment of radiotherapy and surgery or simple radiotherapy. (2) Thoracic tumors: Early esophageal and lung cancers should be treated with surgery; middle and late esophageal and lung cancers should be treated with radiotherapy or surgery; small cell undifferentiated lung cancer should be treated with combination of chemotherapy and radiotherapy. (3) Lymphatic system tumors: Hodgkin’s lymphoma, stage I, II, IIIA radiotherapy is the main treatment, stage IIIB, IV chemotherapy is the main treatment, with local radiotherapy; non-Hodgkin’s lymphoma, stage I, II radiotherapy is the main treatment, stage III, IV chemotherapy is the main treatment, or can be combined with local radiotherapy. (4) Genitourinary system tumors: most of them are mainly treated by surgery, or supplemented by radiotherapy after surgery. Testicular spermatogonia is mainly treated with radiotherapy. (5) Gynecological tumors: radiotherapy is the main treatment for cervical cancer; surgery and radiotherapy are feasible for uterine and ovarian cancers, and the latter can be treated with chemotherapy. (6) Digestive system tumors Surgery for gastric and intestinal cancers is the mainstay; radiotherapy is feasible for pancreatic and biliary tract cancers; rectal cancer can be treated with surgery or palliative radiotherapy. (7) Bone tumors: Osteosarcoma is mainly treated by surgery, and radiotherapy and chemotherapy can improve the therapeutic efficacy; reticulocyte sarcoma of bone and Ewing’s tumor can be treated by radiotherapy, which can be used in conjunction with chemotherapy; and bone metastases can be treated with pain relieving radiotherapy. (8) Neurological tumors Most primary intracranial tumors need postoperative radiotherapy; but medulloblastoma, ventriculoblastoma and germ cell tumor still need to be irradiated for the whole central nervous system; intracranial metastatic tumors are preferred to palliative radiotherapy. (9) Skin and soft tissue tumors: Early stage skin cancers have the same efficacy of radiotherapy and surgery; advanced cancers can be treated with radiotherapy or surgery; melanoma and soft tissue sarcoma are mainly treated by surgery, and the efficacy can be improved by radiotherapy and chemotherapy after surgery. (l0) Breast cancer: early stage cancer can be treated with minor surgery plus radical radiotherapy, which has the same efficacy as radical surgery but preserves the appearance and function of the breast; intermediate stage cancer can be treated with postoperative radiotherapy and chemotherapy to improve the local control; advanced cancer can be treated with preoperative radiotherapy or chemo-radiotherapy and radiotherapy. (l1) Certain benign diseases, such as epidermal hemangioma, long-lasting eczema, skin keloid, neurodermatitis, etc., can also be treated with radiotherapy. 8.What is the position of radiation therapy in the treatment of malignant tumors? Radiotherapy has a history of nearly one hundred years. As early as after the discovery of radium by Madame Curie and the discovery of X-rays by Roentgen, radiation was quickly used in the treatment of malignant tumors. In the 1920s and 1930s, due to the availability of reliable X-ray equipment, radiophysical and radiobiological research made significant progress. in the 1940s, artificial radioisotopes were manufactured, and in the 1950s, cobalt 60 machines were applied to clinical treatment, and the efficacy of radiotherapy began to improve significantly. after the 1960s, various types of gas pedals were produced, and high-energy X-rays and electron beams were used for the treatment of tumors and gradually replaced the ordinary X-ray machines and the 60-second X-rays. After the 1960s, various kinds of medical accelerators were produced to treat tumors with high-energy X-ray and electronic wire, and gradually replace ordinary X-ray machines and 60-cobalt treatment machines. In some developed countries and regions, fast neutrons, protons, negative mesons and heavy particles have also been experimented and gradually applied in clinics. At present, malignant tumors have become the common and frequent diseases in the world, the incidence rate increases year by year, and its mortality rate accounts for the first or second place of various causes of death. Radiotherapy has become one of the main means in the treatment of malignant tumors, and more than 70% of patients with tumors need radiotherapy (including comprehensive treatment and individual treatment). Some malignant tumors can be cured with radiotherapy alone. Moreover, radiotherapy has become a specialized discipline called tumor radiotherapy, including clinical radiophysics, clinical radiobiology and clinical radiotherapeutics, and has developed rapidly in the past 40 years. Some early malignant tumors have high cure rate with radiotherapy alone, such as early nasopharyngeal cancer, cervical cancer, vocal cord cancer, Hodgkin’s lymphoma, skin cancer and so on. The 5-year survival rate of early esophageal cancer, prostate cancer, tongue cancer, etc. are similar to that of surgery, while the functional cosmetic preservation is more satisfactory. Generally speaking, 70% to 80% of the tumor patients who come to the hospital are in the middle or late stage, and most of the patients are inoperable, or have difficulty in resection, or have contraindications to surgery, or are unwilling to have surgery, most of them need to undergo radiotherapy, and many of the patients have better therapeutic effect. Radiotherapy also occupies an important position in the comprehensive treatment of tumors, such as preoperative, intraoperative and postoperative radiotherapy with surgery; radiotherapy before, during and after chemotherapy with chemotherapy; and radiotherapy, surgery and chemotherapy with integrated treatment. In conclusion, radiotherapy is an important and indispensable treatment means for most malignant tumor patients, and malignant tumor patients should pay attention to the radiotherapy department for consultation and treatment. 9. Can radiation therapy cure all diseases? Radiation therapy cannot cure all diseases. However, among malignant tumor patients, most of them need to receive radiotherapy treatment, including radical radiotherapy and palliative radiotherapy. Many cancer patients who come to the hospital for consultation have already reached the middle or late stage of the disease. Radiotherapy can kill most of the tumor cells, so as to achieve temporary control of the tumor, alleviate the symptoms of the patients and prolong their lives, and most of the patients need to cooperate with the surgery or chemotherapy in order to achieve complete control of the local area or to eliminate the potential and existing distant metastatic foci, so as to obtain better therapeutic effects. Radiotherapy is only a localized treatment, and it is often limited by the dose tolerance of normal tissues and organs in the radiation field. In the treatment of many middle and late stage patients, a very high dose is often needed to control the tumor, which will inevitably cause serious early and late damage to the normal tissues next to the tumor in the irradiation field, resulting in unnecessary pain and injury to the patient, which is what the radiotherapists do not want to see. The principle of radiotherapy is to kill the tumor as thoroughly as possible while protecting the function of normal tissues and organs as much as possible, i.e., to increase the irradiation dose of the tumor area and reduce the irradiation of the surrounding normal tissues and organs as much as possible. In clinical tumor treatment, many head and neck tumors, such as maxillary sinus cancer, nasal sieve sinus cancer, oral cavity cancer and laryngeal cancer, etc. still need to be treated with surgery; while parotid adenocarcinoma, thyroid carcinoma and intracranial primary tumors are generally preferred to be treated with surgery. Surgery is generally preferred for gastrointestinal tumors, urinary tract tumors, early lung cancer and esophageal cancer. As for middle and late stage lymphoma, lung small cell undifferentiated cancer and bone marrow tumor, chemotherapy is often the main treatment means. 10.What are the commonly used radiation lines in radiotherapy? There are three types of radiation used in radiotherapy: ① the α, β, γ lines emitted by radioisotopes; ② X-ray therapy machines and various types of gas pedals produce X-rays with different energies; ③ various types of gas pedals produce beams of electrons, fast neutrons, proton beams, negative Woody’s meson beams, and other heavy particles, etc. The first type of radiation can be used as the body’s internal body beam. The first type of radiation can be used for internal and external irradiation; the second, three types of radiation can only be used for external irradiation. Radioisotope radiation α, β, γ three kinds of rays. Due to α ray ionization ability, but weak penetration, an ordinary thin paper can be blocked, radiotherapy basically do not use such rays; β, γ two ray use more, especially γ line is widely used. Natural radium source γ line, in the early days of radiation therapy is used more, but because of its high requirements in terms of protection and many shortcomings, it is now replaced by artificial radioisotopes such as 60 cobalt, 137 cesium and 192 iridium. 60 cobalt γ line is mainly used for external irradiation, while 137 cesium, 192 iridium γ line is mainly used for intracavitary or intertissue insertion therapy. 90 strontium β line is often made β money dresser for the treatment of superficial lesions (such as cornea), but also used 90 strontium β line treatment of skin surface residual lesions. Ordinary X-ray therapy machine produces low-energy (16KV ~ 400KV) X-rays, mainly for the treatment of more superficial tumors. The high-energy (more than 2MeV) X-rays produced by various gas pedals can treat almost any part of the tumor, especially good for the deeper tumor treatment; and the electron beams produced by them are commonly used for the treatment of superficial or eccentric tumors. For various gas pedals produce fast neutrons, protons, Woods negative mesons and heavy particle streams such as helium, carbon, nitrogen, oxygen, neon, etc., their applications are not widely used in developed countries because one of the reasons is that the price is too expensive, and the clinical effect is not certain in most tumors except for a small number of tumors with good effect. There is only one fast neutron therapy for parotid adenocarcinoma, prostate cancer or tumor with poor effect of general radiotherapy, such as soft tissue sarcoma or other recurrent tumors in Beijing area of China. 11. What is the difference between X-ray and Y-ray? People usually called X-rays and γ photons, just with the word “light” to illustrate the nature of such rays, because they are members of the family of spectra. They and visible light, radio waves, are essentially electromagnetic waves, have the characteristics of light, just different energy. x-ray energy is the highest, the widest range, from ultraviolet up to dozens or even hundreds of megaelectronvolts (MeV), followed by visible light, infrared light, until the lowest energy of radio waves. Due to the high energy of X-rays, can penetrate a certain thickness of material; the higher the energy, the thicker the penetration, so the medical commonly used to fluoroscopy, photographs and radiation therapy. X-rays and wires are not fundamentally different from each other, only in the way they are generated. From history and custom, people by high-pressure equipment (such as gas pedal, deep, medium and contact therapy machine) artificially produced by the invisible rays called X-rays; and the radioactive isotopes produced by the rays are called & gamma; line, such as 60 cobalt therapy machine 137 cesium, 192 iridium rear-loaded therapy machine is produced by the y line. Due to the different energies of different energy X-ray therapy machines and gas pedals produce different energies of X-rays, there are different applications in clinical radiotherapy. High-energy X-ray (more than 2MeV) application range with 60 cobalt γ line (average energy 1, 25MeV), they have the following advantages compared with low-energy X-rays (below 400KV): ① strong penetration, high percentage of depth of the dose, suitable for the treatment of deeper tumors; ③ protection of the skin, because the maximum absorbed dose in the skin at a depth of 4 ~ 5mm or deeper, the dose of skin relatively small; ③ bone and soft tissues, skin and soft tissues. Small; ③ Bone and soft tissue have the same absorbed dose, small damage to bone, and the treatment dose is more accurate; ④ Small side scattering, protecting the normal tissues outside the edge of the shot field and reducing the whole body dose; ⑤ 60 cobalt & gamma; line therapy machine still has the advantages of economy, reliability and so on. 12, what is the electron line, what are its characteristics? Electrons are the smallest charged particles, different from X-ray or γ line, it is accelerated to a certain high energy in electron gas pedal, and is directly induced (electron beam) to treat tumor. The high-energy electron beam can directly kill or ionize cells. Its tissue absorbed dose distribution characteristics are as follows: (1) From the surface of the skin to a certain depth, the dose is high and relatively uniformly distributed, and with the increase of energy, this depth is also increasing. Dose built-up area is very narrow, and quickly reach 100%. The size of the surface dose varies according to the energy: low energy, low surface dose; high energy, high surface dose. For example, at 7 MeV, the surface dose is 85%; at 18 MeV, the surface dose is 98%. Thus, it cannot protect the skin. (2) After a certain depth, the dose suddenly drops. If the clinician selects the lesion in the 80% area, the normal tissue after the lesion will receive a very small amount. However, as the energy increases, this feature gradually disappears, and for 45 MeV electron beam, this feature is almost completely lost. Therefore, the electron energy of the electron gas pedal is selected too high is of no practical significance, generally the most useful electron energy is selected within 25MeV. (3) Different radiation field has an effect on the percent depth dose: at low energy, the effect of the field is small; at high energy, the effect of the field is very large, i.e., the field increases, the depth dose increases. (4) It can also be seen from the equivalent dose distribution curve: the curve of the incident surface is concentrated, gradually spread out with the increase of depth, and there is a large side scattering; the curvature of the curve varies with the depth, the area of the field and the electron energy, and the range of variation is relatively large. In general, and especially for large fields, the center portion of the curve is parallel to the incident surface, regardless of whether the incident surface is flat or curved. This is beneficial to the clinician when considering irregular surface incidence. 13. Under what circumstances is treatment with electron beams used? It was mentioned earlier that there are four major characteristics of the dose distribution of electron beams absorbed in tissues, and the most important are the first two characteristics: ① From the incident surface to a certain depth, the dose is high and uniformly distributed; with the increase in energy, this depth is also increasing. The built-up area of the dose is very narrow and reaches 100% very quickly, so it cannot protect the skin effectively. ②After a certain depth, the dose suddenly decreases. If the clinician selects the lesion in the 80% area, the normal tissue behind the lesion receives very little dose, so it can protect the normal tissue and organs behind the tumor very well. However, with the increasing energy, this feature gradually disappears, and the best choice of electron energy for clinical application is within 25MeV. According to the above characteristics, high-energy electron beam is very suitable for the treatment of those superficial and eccentric tumors, and it is mostly used for single-field irradiation, i.e. irradiation from one direction. If necessary, tissue equivalents can be used appropriately to improve the dose distribution and meet the needs of clinical treatment. Complementary radiotherapy of cervical lymph nodes is aimed at protecting the deep cervical spinal cord from over-irradiation; irradiation of the chest wall and internal breast lymphatic chain after breast cancer surgery are irradiated with electron beams in order to reduce the amount of deep lung tissues received to improve the quality of survival; there are also skin tumors, such as skin cancers, melanoma and mycosis fungoides, etc.; and nasal sieve sinus tumors are also often treated with electron beams. Because the electron energy induced from the gas pedal is adjustable, the appropriate electron energy can be selected for treatment according to the different depths of the lesions. In addition, the use of multi-field and appropriate application of other technologies can also be used to treat deep tumors, but this treatment technology is basically not used clinically, and replaced by high-energy X-ray or 60 cobalt & gamma; line treatment. In addition, intraoperative radiotherapy can also be considered to be treated with electron beam, because the exposed tumor lesion can receive high dose irradiation, and the normal tissue behind the lesion is protected by low dose. 14.What is contact therapy machine? What diseases can it treat? A contact therapy machine is an X-ray machine with a tube voltage between 10 and 60 kVT. X-rays are generated by electrons emitted by a cathodic tungsten filament in a high vacuum tube sphere after a high-speed movement against an anodic target. Due to the low voltage of the tube, the X-rays produced are of low energy, with very low penetration capability and a relatively small irradiation area. Clinically, it is generally used for the treatment of superficial skin surface or body cavity diseases. Such as epidermal hemangioma, long lasting eczema, neurodermatitis, hand or foot parts of the fingers, toes warts and other benign lesions; can also be used for eyelids, oral cavity, superficial lesions, or other parts of the skin of the body basal cell carcinoma and other lesions. Generally, patients who receive this treatment will have radiation dermatitis and darkening of the skin due to pigmentation, which are normal skin reactions. This is a normal skin reaction. The reason for this is that the maximum absorbed dose of X-rays from the treatment machine is on the surface of the body or mucous membranes, which results in too much exposure. When the treatment is over, the skin of the irradiated area will gradually return to normal. Of course, acute radioactive mucositis can also occur in the oral cavity, and the irradiated mucosa will gradually return to normal after radiotherapy. Please don’t worry about it, and complete the treatment on time under the doctor’s guidance. 15.What is a deep X-ray machine and under what circumstances is it suitable for use? Deep X-ray therapy machine usually refers to the X-ray machine with tube voltage between 180 and 400 kVT, which is the same as the contact therapy machine in terms of structure and the principle of X-ray generation. However, because the tube voltage of this machine is higher than that of the contact therapy machine, the intensity and penetrating ability of the X-rays produced by it are larger, so it is mostly used for the treatment of benign diseases and malignant tumors located in the more superficial area. Therefore, it can be used as an auxiliary means of 60 cobalt treatment machine and gas pedal high-energy X-ray treatment, supplementing the insufficient dose of superficial parts. According to the needs of treatment, the treatment machine can be divided into fixed irradiation type, swing irradiation type and rotating irradiation type 3 kinds in the design, so that the deep X-ray treatment machine is more widely used. Deep X-ray machine is often used in the treatment of benign diseases such as skin scar, armpit odor, neurodermatitis, corns, deeper parts of hemangioma and penile cavernous sclerosis, and the effect is more ideal. For skin cancer, skin adnexal cancer, neck lymph node metastatic cancer, complementary radiotherapy has also achieved obvious efficacy. Pain relief radiotherapy for bone metastatic cancers in shallower parts (such as rib or clavicle metastatic cancers) has better efficacy, which is due to the larger photoelectric effect of the X-ray of this energy band and the higher X-money absorption of the bone. Due to the low energy of this treatment machine, the dose in the deep part of the tissue is low, which is not suitable for the treatment of deep tumors, and the skin reaction is heavy, so it can only be used for the treatment of tumors in the more superficial parts. In many areas of our country, this machine is still widely used as a supplement of 60 cobalt therapy machine and gas pedal therapy. 16.What is 60 cobalt therapy machine and what are its advantages and disadvantages? 60 cobalt therapy machine is commonly known as “cobalt cannon”, 60 cobalt is a kind of artificially produced radionuclide. Cobalt cannon” is to 60 cobalt as a radioactive source, with & gamma; ray killing cancer cells, the implementation of tumor treatment device. 60 cobalt machine consists of the following parts, a sealed radioactive source; a source container and protection head; with a switch of the wire device; with a directional beam limiting light limiting cylinder, supporting the mechanical system of the head and its ancillary equipment and a console composition). The advantages are: (1) high ray penetration i.e. can treat tumors of considerable depth. (2) protection of the skin 60 cobalt ray in the subcutaneous 4 ~ 5 mm at the maximum absorption of energy, the epidermal dose is relatively small. (3) Bone and soft tissue have the same absorbed dose, i.e., when the ray passes through, the bone and soft tissue absorb basically the same ray, unlike the common X-ray, the bone absorbs more than the soft group, which causes great harm to the bone. (4) Small side scattering Protect the normal tissues outside the periphery. (5) Economical, reliable, simple structure, easy maintenance. Disadvantages: (1) 60 cobalt energy single. (While the gas pedal can have a variety of energy X-rays and electron beams). (2) 60 cobalt depth dose is on the low side, in order to improve the dose in the depth, it is necessary to improve the external irradiation dose, resulting in an increase in the whole body dose. Gas pedal depth dose is high, and systemic exposure is low. (3) The half-life of 60 cobalt is short (about 5 or 3 years), so it is necessary to replace the radioactive source regularly. (4) 60 cobalt is a radionuclide, there is a continuous release of rays, the protection is complicated, the staff is subject to a large amount. (5) 60 cobalt penumbra problem, so that the field of normal tissue affected by a certain dose. In short, “cobalt machine low cost, easy maintenance, so that it is faster than other radiotherapy equipment development, is still the main equipment for radiation therapy. 108, what is a gas pedal? Gas pedal is the artificial use of electric and magnetic fields of force, the charged particles accelerated to high energy of a device or equipment. Gas pedal can produce both high-energy electron beams, high-energy X-rays and fast neutrons, the energy range of 4 to 50 MeV. 17. What kinds of gas pedals are commonly used in radiotherapy and what are their characteristics? There are three types of gas pedals commonly used in radiotherapy: electron induction gas pedal, electron linear gas pedal and electron cyclotron. The advantages of electron induction gas pedals are that they are technically simple, low in manufacturing cost, and can easily achieve high energies such as 25 mega electron volts. The electron lines it produces, the output is large enough, the energy adjustable range is wider. The disadvantage is that the X-ray output is relatively low, the irradiation field is also small. At the same time, this equipment is large in size and heavy in weight, which brings certain difficulties to the installation and medical treatment. The advantage of electron linear gas pedal is to overcome the above shortcomings, it has a high enough output for both electron and X-ray, which has the potential to expand the irradiation field, and can use the deflection system to do isocenter treatment. The disadvantages are complex structure, expensive cost and high maintenance requirements. Electron cyclotron has both the economy of the electron induction gas pedal, but also has a linear gas pedal of high output characteristics of the electron and X-ray energy in the medical use are ideal. In short, it is simple structure, small size, low cost, is the development direction of linear gas pedal.
18.Is the therapeutic efficacy of the gas pedal necessarily better than that of 60 cobalt? There is no significant difference between the efficacy of the two treatments. Since the introduction of gas pedals in China in the late 70s, many patients and even some medical personnel are often superstitious that it has special effects, and from the clinical observation in the past ten years, the efficacy of gas pedal treatment has no more superiority. The radiotherapy department of our hospital summarized the radiotherapy of nasopharyngeal cancer patients in 88 years, and the gas pedal group (301 cases), compared with the 60 cobalt group (293 cases), the two groups were similar in terms of the treatment results such as the 5-year survival rate, the local recurrence rate, the mortality rate, the radiological sequelae, and the labor force after the treatment, and the therapeutic efficacy was also basically the same. Of course, due to the leap of social economy and science and technology development, taking into account the 60 cobalt machine still has some shortcomings, such as the depth of the amount of low, energy is relatively single, can not meet the patient and radiotherapy workers of a variety of needs, while its radiation hazards caused by the staff, poor protection, etc., so that the gas pedal is more and more widely used. However, the gas pedal is expensive, difficult to maintain, once the machine failure will also affect the patient treatment. So for developing countries (including our country), 60 cobalt machine is still the main radiotherapy equipment, and its economic, reliable, easy maintenance by the majority of medical workers favor. 19.What is fast neutron therapy and what are its characteristics? Fast neutron therapy is what people call “neutron therapy for cancer”, which is to use neutron beam current to effectively kill cancer cells and achieve the purpose of improving the local control rate of cancer and prolonging the survival period of cancer patients. Neutrons are non-electrically charged particles, which can be categorized into thermal neutrons, slow neutrons and fast neutrons according to the energy they possess. Fast neutrons are high LET rays (it is a specialized term, short for linear energy transfer). It has the characteristics of high LET rays, which are as follows: biological aspects: ① low oxygen enhancement ratio, can overcome the lack of oxygen tumor cell resistance to rays, treatment of general radiation resistant tumors; ② strong relative biological effect, the biological effect produced by the same absorbed dose, the neutron is about 3 times larger than the role of ordinary X-rays; ③ tumor cell dynamics, the cell cycle of the different phases of the same time with the sensitivity of the neutron has no difference, and thus Fast neutrons have strong killing effect on tumor cells. Physical characteristics: ①Fast neutron beam is similar to X-ray (photon beam). Depth dose decreases exponentially; ② poor penetration, the depth dose can increase with the distance from the surface of the neutron source; ③ fast neutron beam penumbra is large, the dose of the edge of the field is large, the skin and the subcutaneous tissue reaction is large. In conclusion, fast neutrons rely on its superior radiobiological properties to effectively kill certain tumors, and have its strict indications. 20. What is the current status of fast neutron therapy in China? The current status in China is led by the Institute of High Energy Physics of the Chinese Academy of Sciences (IHEP), which has established the Beijing Fast Neutron Cancer Research Collaboration Group and is responsible for the implementation of the fast neutron clinical treatment. The Institute of High Energy Physics (IHEP) has a fast neutron cancer research device, which was completed in June 1989 and started in November 1991 to provide fast neutron clinical treatment. The work centers around two major topics: the correct selection of cases for fast neutron indications and high-level physical and technical work, with the aim of improving the local control rate and reducing the radiation damage caused by neutrons, which is also a common problem in the international research field of fast neutron therapy for cancer. Over the past six years, more than 300 patients have been admitted and treated for various cancers, including: parotid gland cancer, prostate cancer, soft tissue sarcoma, lung cancer, mesothelioma, pelvic cancer, head and neck cancer, intestinal cancer and so on. The most successful fast neutron radiotherapy is for malignant parotid tumors, and a comparative study of the efficacy and side effects of simple fast neutron radiotherapy and hybrid radiation radiotherapy has been done for certain cases. At present, the research on fast neutron therapy is continuing, and a consensus has been reached on the status of fast neutron therapy for cancer in radiotherapy. With the deepening of clinical work and research, work and research with Chinese characteristics are being explored under the strong support of the National Science and Technology Commission and other departments. 21.What is brachytherapy? Brachytherapy is to place the radioactive source applicator on the surface of the tumor in the lumen of the human body or implant it into the tumor with a needle, and then through the computer control system, the radioactive source is used to carry out radiotherapy directly on the surface of the tumor or inside the tumor. At the beginning of this century, when the brachytherapy, the medical staff use the manual operation to place the radiation source in the tumor body, and suffer from a large amount of radiation, and in the 50’s due to the unfolding of the rear-loading technology, the staff carry out the operation and position under the non-radiation, which greatly reduces the amount of the staff suffer from the tumor body, and improves the accuracy of the treatment. It includes five types of intracavitary, intratubular, intertissue insertion, intraoperative placement and model dressing. 22.What are the types of brachytherapy and what are the advantages and disadvantages of each? There are two main types of brachytherapy. Categorized by dose rate, less than 2Gy per hour for low dose rate, more than 12Gy per hour for high dose rate. The characteristics of low-dose-rate brachytherapy are: the treatment time after placing the radioactive source is 37 hours to 3 days; the damage to normal tissues is small; and the efficacy is good for the treatment of gynecological cancer. Disadvantages: ① nursing staff are exposed to large amounts of radiation; ② due to the long time of placing the source, the position of the applicator is easy to change; ③ low-dose-rate radioactive sources can not be miniaturized. High-dose-rate brachytherapy features: ① short treatment time without hospitalization; ② accurate positioning; ③ the 192 iridium radioactive source can be miniaturized (can be used for endotracheal tube, implantation, etc.) wide range of therapeutic uses. Disadvantages: ① greater damage to normal tissue; ② heavy local reaction. At present, almost all of the domestic brachytherapy is a high dose rate type. 23. What is intracavitary radiotherapy and which tumors can it treat? Intracavitary therapy is a kind of brachytherapy that utilizes the body’s own cavity and tubes to place treatment tubes. The tube is usually placed in the treatment area through endoscope or according to the anatomical part of the body and the plastic tube of 1.7~2.0mm in diameter is placed in the treatment area, and then the treatment is carried out according to the corresponding steps. It can treat nasopharyngeal cancer, esophageal cancer, tracheal cancer, bronchial cancer, rectal cancer, cervical cancer and so on. 24. What are the operation steps of Intracavitary Radiotherapy and what are the precautions? (1) After choosing suitable patients, the doctor should explain the purpose and method of treatment to the patients before treatment and obtain their cooperation. (2) Treatment of local lesions and control of inflammation are carried out before treatment, and auxiliary examinations such as blood phase and X-ray are done at the same time. (3) After local anesthesia, the tube is placed and positioned, and the tube is inserted into the lesion with the corresponding applicator, and the positioning film is taken after positioning and correction under the simulator. (4) On the localization film, the doctor in charge draws out the treatment range, determines the treatment dose, and designs the treatment plan through the computer. (5) The technician in charge sends the patient into the machine room, connects the applicator to the brachytherapy machine and starts radiotherapy. (6) After the treatment is finished, pull out the applicator and take a short rest, and the patient can leave only if he/she is not uncomfortable. Precautions: (l) after the treatment, to the patient to explain the possible reactions and treatment; (2) operation, the technique should be gentle, to reduce unnecessary stimulation; (3) routinely tell the patient to take X-rays or imaging films, as an observation of the efficacy of the treatment and follow-up comparison; (4) such as difficulties in eating and hemoptysis after the treatment, no need to be nervous, and find the doctor to prescribe the symptomatic treatment can be improved. 25.What is intertissue implantation and which tumors can it treat? Intertissue implantation refers to a kind of brachytherapy technique in which intertissue implantation needles or treatment tubes are directly inserted into the tumor body for radiotherapy in a certain order. It is suitable for patients with recurrent or residual tumors after radical radiotherapy, where the anatomical site permits or is necessary to maintain function, and where the lesion is located on and near the surface of the body. It can treat breast cancer, tongue cancer, oral cavity cancer, prostate cancer, pleural mesothelioma, brain tumor and so on. 26.What are the operation steps of inter-tissue insertion and implantation technique and what precautions are there? The steps are as follows: (1) Adopt different positions according to different parts of the lesion and perform local anesthesia. (2) According to CT, isotope scanning, magnetic resonance imaging, etc. to determine the target area of treatment, the number of layers of implanted needles, the number of roots, the depth, the layout of needle spacing, etc.. (3) Design the treatment plan and determine the treatment dose. (4) Make templates, punch holes, and prepare for treatment, then implement treatment. Precautions: (1) Strictly follow the aseptic technique. (2) Insertion must be based on the principle of Paris dosimetry system. (3) Before inserting the needle each needle hole with 2% lidocaine line infiltration anesthesia, after the end of the treatment in order to pull out the needle, the needle hole with a sterile dressing package. (4) There is localized pain at the eye of the needle, symptomatic pain relief is sufficient. 27, what is the analog positioning machine, what is its role? Simulation positioning machine is a simulation of radiation therapy machine (such as medical gas pedal), the geometric conditions of treatment and set out the irradiation site of radiation therapy auxiliary equipment, it is actually a special X-ray machine. It is a special X-ray machine. Its function is just like its name, which is to simulate positioning. So what is meant by simulated positioning? It is actually: when the patient is diagnosed with tumor and prepared for radiotherapy, a thorough radiotherapy plan should be made before the radiotherapy, and then the irradiated part should be determined on the positioning machine and marked well before the medical gas pedal or 60 cobalt treatment machine can be used to carry out the radiotherapy. This is where the simulator comes in. 28 Why is it necessary to make a mark on the skin with red ink during radiotherapy? When a patient is diagnosed with a tumor and needs radiotherapy, the doctor has to give the patient a good pre-radiotherapy examination and then make a radiotherapy plan for his/her lesion based on the results of physical examination, X-ray, CT and MRI. The patient’s tumor site will be projected onto the corresponding skin by setting the irradiation range through the anatomical structure or simulated positioning machine, so the doctor will have to make skin marks on the skin with red ink. When the patient undergoes radiation therapy, the technician positions the patient and then uses the radiation therapy machine to deliver radiation therapy to the patient against the skin marks. It is important to let the patient know the importance of the skin mark and to keep the skin irradiation field as clear as possible to ensure successful completion of radiation therapy. 29. Why are modules of various shapes sometimes made of low melting point lead? We all know that the melting point of lead is as high as 327 degrees, which is not conducive to making modules of various shapes, unlike low melting point lead, which belongs to an alloy consisting of 50% bismuth, 26,7% lead, 10% cadmium, 13,3% tin, and has a melting point of about 70 degrees. Using this feature of low melting point lead, together with the thermal resistance wire cutting technology to make different shapes and sizes of foam made of inner mold, it is easy to process into a variety of different shapes of the module. The module is firmly fixed to the gas pedal and can be freely used for treatment at different angles. The module can be positioned quickly and accurately, and the low-melting-point lead can be recycled after treatment. By utilizing the above characteristics of low-melting-point lead, various modules are made to fit the size and shape of the irradiated area according to the irradiation range, e.g., if the irradiation range is elliptical, the inner contour of the module will be elliptical. At the same time, the use of modules can also protect normal tissues and important organs in the irradiation field from unnecessary irradiation, for example, in order to protect the eyeballs during radiotherapy, a cylindrical module can be made, and the module can be fixed in the corresponding position during radiotherapy, blocking off the rays that irradiate the eyeballs, so as to avoid radiation damage. 30. Why is wax block sometimes used and what is its function? The relevant properties of wax are the same as human tissues, it is “human tissue equivalent material”, and its scattering and absorbing effects on radiation are similar to those of human tissues; in addition, the melting point of wax is very low, so it can be easily made into different shapes, sizes and thicknesses according to different needs after dissolution, and it can be pressed to make the wax block and the surface of the human body fit well when it has not yet been cooled down completely. By utilizing the above features, the wax blocks can be placed at the corresponding positions to improve the dose distribution in the irradiated area and make the dose distribution more reasonable. For superficial tumors, such as skin cancer and superficial metastatic lymph nodes, due to the existence of the “dose completion zone” from the body surface to the dose maximum (when irradiated with high-energy X-rays, such as 6MV-X-rays or 8MV-X-rays, and electron rays, the radiotherapy dose gradually increases from the body surface to the body, and the maximum dose is reached at a certain depth, which is referred to as the “dose completion zone”). We call the area from the surface of the body to the maximum dose the “dose build-up area”), which results in insufficient irradiation dose to the relatively superficial part of the tumor. Therefore, a wax block of appropriate thickness can be placed on the surface of the tumor, for example, when irradiating with 6MV-X or 8MV-X, the thickness of the wax block should be 1~1.5 cm, so that the area of maximum dose can be “lifted up” to the part of the tumor that needs to be irradiated, and thus the tumor area can be irradiated in a more reasonable way to get a better therapeutic effect. 31. Why is it sometimes necessary to put treated pig skin on the skin? The composition and structure of pig skin is almost the same as human tissue, which is a better “human tissue equivalent material”, and the pig skin has good adhesion to the human body surface, so it is easy to take the material, and it can be preserved and used for a long period of time after being treated with some chemical drugs. Therefore, for patients with skin cancer, breast cancer, chest wall involvement and other superficial tumors, the treated pig skin can be placed on the surface skin of the tumor when radiotherapy is performed with electron beam, so that the surface of the body can be raised to the maximum radiation dose, i.e., the “dosage built-up area”, to the needed and more superficial part of the skin, so that the skin can get a larger radiation dose to get a better radiotherapeutic effect. Of course, because the pig skin is generally thinner, so it is mostly used for radiotherapy with lower energy electron beams. 32.What are the common positions used in radiotherapy? The position of radiotherapy is decided according to the location of the tumor, different treatment methods and the actual condition of the patient, etc. At the same time, the position must be repeatable and easy to be accepted and realized by the patient. Generally, the commonly used positions are supine position and prone position. Of course, sometimes, in order to facilitate treatment and acceptance by patients, it is necessary to put pillows on the head or back, or let patients raise their hands up or put them in a fixed position. For example, for the more common esophageal and lung cancers, basically, supine and prone positions are used in the whole treatment, and most of them are supine and prone alternately, i.e., supine today, prone tomorrow; of course, if the patient is weak and old, supine can also be used only. When horizontal field irradiation is needed for esophageal cancer and lung cancer, in order not to expose both upper limbs to irradiation, it is necessary to hold both hands over the head. If the doctor tells you to hold your head when radiotherapy is given, it is not possible to put both hands on both sides of the body as usual, in this way, the scope of radiotherapy will change and the effect of treatment will also be affected. In addition, side-lying position is also commonly used, such as head and neck tumor and brain tumor radiotherapy commonly used side-lying position. 33. How does the different body position during each treatment affect the treatment? As mentioned above, the position of radiotherapy is decided according to the site of lesion, different treatment methods and the specific conditions of the patient. The treatment position must be reproducible, easy to be accepted by the patient and convenient for treatment, and these factors are necessary to achieve good radiotherapy results. Only the same body position each time can ensure the same range of irradiation each time, and also can make the irradiated tumor area get enough radiotherapy dose, and at the same time, make the surrounding normal tissues and vital organs not be irradiated or less irradiated as far as possible. On the contrary, if the body position is different during each irradiation, the irradiation range will be changed each time, and the irradiated tumor area will not get enough radiotherapy dose, while the surrounding normal tissues and organs that should not be irradiated will be over irradiated. This may reduce the efficacy of radiotherapy for tumor, make the tumor easy to recur and metastasize, and increase the radiation damage of normal tissues and organs, and even cause serious sequelae of radiotherapy, such as tissue ulceration, skin fibrosis and hardening affecting the blood supply, and even complete loss of organ function, such as inability to lift the upper limbs and paralysis. Therefore, patients should remember the instructions of medical personnel, remember the position of radiotherapy, and try to make the position consistent each time, in order to get the best radiotherapy effect. 34. What are the methods of fixed position and what are the advantages and disadvantages of each? Fixed position refers to fixing the patient’s position in a suitable position with the help of some fixation devices. This ensures the repeatability of the patient’s position during radiotherapy, thus ensuring the accuracy of radiotherapy. There are many methods, and the commonly used methods are described as follows: (1) Use foam board to cushion the head or body. When nasopharyngeal carcinoma or brain tumor is treated in side-lying position, a certain height of foam board is used to make a cushion pillow on the head, so that the level of radiotherapy site is parallel to the treatment bed; in addition, when medulloblastoma is treated in whole-brain and whole-spinal cord radiotherapy, the patient should take the prone position with foam board on the chest, abdomen and body part, and the head is cushioned with chin-frontal pillow, which makes the spine straighten up as much as possible and facilitates the treatment. Although this method is simple and easy to take materials, the production method is simple, but not fine enough. (2) When radiotherapy is performed on chest wall and inner breast area after radical mastectomy for breast cancer, in order to make the irradiated area level with the bed surface, a wedge-shaped board of 10 degrees or 15 degrees can be padded on the back. This method is more practical but not delicate enough. (3) When breast cancer patients undergo further radiotherapy after breast preservation surgery, a wedge-shaped plate made of plastic sheet should be placed on the back, and there is a handle on the head side of the plate, which is specially used to fix the uplifted hand in a relatively constant position. This can make the irradiated part parallel to the bed surface and have a relatively fixed position during radiotherapy, and can make the irradiated area fully exposed, and does not cause the sick side of the upper limb to be irradiated, but this wedge-shaped plate is a little poor in adjustability. (4) In the treatment of pituitary tumor, the patient takes the supine position and puts a “B”-shaped pillow on the head, which is consistent with the physiological curvature of the human body, so it can fix the head better, and puts a suitable wedge plate under the “B”-shaped pillow on the basis of which, it can better satisfy the needs of patients with different pituitary tumors in different treatments. This method is practical and easy to implement, and is more frequently used in radiotherapy of brain tumor. (5) The best fixation method is to make specific fixator according to different treatment needs of different patients, such as making specific plastic mask for patients with brain tumor or nasopharyngeal carcinoma, so that the patients are fixed no matter what position they are in. In addition, specific grooves can also be made for the body, so that the patient’s body can have better repeatability and accuracy in radiotherapy, but this method is more expensive and has not been popularized yet. 35. What is computerized treatment planning system and what is its importance to radiotherapy? Computerized treatment planning system is in radiotherapy before the patient’s CT, MRI or other information into the computer, the computer according to these data and treatment requirements of radiotherapy dose distribution calculation, and the treatment program for the preferred system. Its importance lies in: (l) Using computerized treatment planning system, the dose distribution of different treatment methods can be calculated on the computer before radiotherapy, and the most reasonable dose distribution plan for tumor treatment can be selected according to the calculation results and put into practice. (2) Radiotherapy for tumor should not only make the tumor get the maximum lethal dose, but also make the surrounding normal tissues, especially the important organs, such as the spinal cord, brain stem and eyeballs, suffer the least radiation damage, that is to say, try to make the normal tissues and organs suffer less from radiation exposure. Through the computerized treatment planning system, we can get the dose size of the surrounding normal tissues and organs under different treatment plans before radiotherapy, from which we can choose the appropriate treatment plan to ensure the minimum radiation damage to the surrounding normal tissues and organs. Of course, sometimes the irradiation of normal tissues and organs around the tumor is unavoidable, but it can not exceed a certain limit, such as the spinal cord can not be more than 4,000 hgf, otherwise it will cause paralysis of the patient. (3) For patients with intracavitary radiotherapy, computerized treatment planning system is more important, through which the residence time and travel speed of radiation sources in different parts of the tumor can be determined to ensure the reasonable dose distribution in the tumor area, so as to make the tumor get more effective radiotherapy. 36. How to make treatment plan by computer? (1) Firstly, make CT or X-ray localization film of the tumor site (for intracavitary treatment), or take out the outer contour of the body part where the tumor is located (e.g. for breast cancer radiotherapy); (2) Determine the irradiation range on the CT or X-ray localization film and give the irradiation limit of the surrounding normal tissues and important organs, and the conditions and methods of irradiation, etc.; (3) Physicists input the relevant information and conditions into the computer, which applies the corresponding software to determine the dose distribution under this condition. (3) The physicist inputs the relevant information and conditions into the computer, and the computer applies the corresponding software to calculate and optimize the various treatment plans under these conditions, from which the most ideal treatment data are derived, such as the most suitable type of radiation (X-ray or electron beam), the angle of the gas pedal rack, the size of the irradiation range, the dose size of each irradiation field, whether or not to add wedges and blocks, etc. Of course, the final implementation of the treatment plan must be carried out. Of course, the final implementation of the treatment plan must also be confirmed by the clinician under the simulator. 37.At present, the common method of radiotherapy is to irradiate once a day and five times a week, what is the rationale for this? One of the basic principles of tumor treatment by radiotherapy is to make the tumor achieve maximum control and “kill”, while the normal tissues and organs around the tumor only suffer minimum damage. As far as the tumor tissue is concerned, the more sensitive it is to radiation, the better the therapeutic effect of radiotherapy is likely to be. The radiosensitivity of the tumor tissue is related to the number of tumor cells in each “growth stage” and the oxygen content in the tumor tissue. Tumor cells have different “growth stages”, among which the cells in the “cell division stage” are the most sensitive to radiation, while the cells in the “quiescent stage” are not sensitive to radiation. Each time when the tumor tissue is irradiated, only the more sensitive cells are selectively killed, while the insensitive cells are still alive and continue to carry out the proliferation activities of their different “growth stages”, from which some cells enter the more sensitive “growth stage”, and then selectively kill the sensitive cells when the next radiotherapy is given, so that the tumors will get smaller and smaller after the radiotherapy. In terms of the oxygen content of the tumor tissue, the higher the oxygen content is, the more sensitive it is to radiation, on the contrary, when the oxygen content is low, it is not sensitive to radiation. Each time when radiotherapy is given, the tumor cells with high oxygen content can be fully killed, so there are more cells with low oxygen content left, and some of these cells with low oxygen content can be transformed into cells with high oxygen content in the intervals between radiotherapy, and when the next radiotherapy is given, these cells with high oxygen content will be more sensitive to radiation, and then some tumor cells will be killed, and then the tumors will be gradually reduced after radiotherapy one at a time. Therefore, from the perspective of tumor tissue, fractionated radiotherapy can better achieve the therapeutic purpose. As far as normal tissues are concerned, each radiotherapy can also cause a certain degree of damage (of course, much smaller than the damage of tumor tissues), and after fractionated radiotherapy, normal tissue cells have sufficient time to repair during the intervals, thus reducing the damage of radiotherapy to normal tissues. Some studies have shown that increasing the radiotherapy dose and shortening the total duration of radiotherapy will increase the damage of radiation to normal tissues, therefore, fractionated radiotherapy is also conducive to the repair of normal tissues. As for the standard program of radiotherapy once a day and five times a week, it is developed from decades of experience and is a better mode of radiotherapy. 38. Why do some patients need to be irradiated twice or thrice a day and what are the benefits of this treatment? In the clinic, we call this radiotherapy method of irradiating twice or three times a day, with an interval of 4-6 hours, with a daily dose smaller than the conventional dose of 200 sigmoid (mostly 115-120 sigmoid each time), with the total course of treatment remaining unchanged or slightly prolonged, and with an increase in the total dose, “hyperfractionated radiotherapy”, which is a useful improvement in order to increase the effect of radiotherapy for tumors. The advantage of this treatment is that it improves tumor control and is expected to increase patient survival; at the same time, it does not increase the damage to normal tissues and organs in the long run. This treatment is mainly beneficial for slower growing tumors such as head and neck tumors and bladder cancer, but not for tumors that are sensitive to radiotherapy, such as lymphomas and seminomas. Of course, during this kind of treatment, the patient’s radiotherapy reaction at that time may be aggravated, for example, when patients with recurrent nasopharyngeal cancer are treated with this method, the possibility of redness, swelling and even rupture in the patient’s oral cavity is much greater than that of ordinary one-day radiotherapy. 39. In the course of radiotherapy, the treatment is interrupted for a period of time due to various reasons, how does it affect the efficacy? In the past years, there is a radiotherapy method called “segmental radiotherapy”, which is to divide the conventional continuous radiotherapy into two phases, with an interval of 2-3 weeks between the two phases, and as a result, after many years of clinical observation, it is found that this treatment method reduces the effect of tumor radiotherapy. This also shows that it is inappropriate to interrupt the treatment for a period of time during radiotherapy for various reasons, and the result is that the therapeutic effect of the patient decreases, which is related to the “repopulation” of tumor tissues in the intervals. Therefore, from the patients’ point of view, they should try their best to cooperate with the doctor’s treatment, for some overcoming radiotherapy reactions such as mild eating pain and mild nausea, besides the doctor’s appropriate treatment, the patients should set up firm confidence and try their best to overcome them, and they should not stop or give up the treatment on their own initiative when they have a little discomfort; from the perspective of the family members, they should not make the patients pause the radiotherapy because of some family or social trivial matters. Of course, if the reaction of radiotherapy is very serious and the patient can not tolerate it, the patient can take a proper rest under the guidance of the competent doctor, but the shorter the rest time, the better. 40. How long does a course of radiotherapy take? The time needed for one course of radiotherapy depends on the nature of the tumor. It depends on the nature of the tumor, the early or late lesion, the purpose of treatment, the physical condition of the patient and other factors, and generally takes 4 to 6 weeks. For relatively early lesions, radical radiotherapy with radiotherapy as the main treatment requires longer time, generally 5-7 weeks, such as esophageal cancer radical radiotherapy generally requires 6-7 weeks; palliative radiotherapy for late lesions requires shorter time, generally 3-5 weeks, such as multiple metastatic tumors in the brain, which can generally be controlled and completed within 3-5 weeks. Radiotherapy for sensitive tumors generally requires shorter time, such as 3½ to 5½ weeks for lymphoma; while tumors with poor sensitivity to radiotherapy, such as fibrosarcoma, require 6 to 8 weeks. Preoperative radiotherapy for improving surgical resection rate and reducing recurrence usually takes 4 to 5 weeks, such as preoperative radiotherapy for cervical esophageal cancer which takes 5 weeks; postoperative radiotherapy for consolidating therapeutic effect usually takes 5 to 6 weeks, such as postoperative radiotherapy for rectal cancer which takes 5 weeks. For those who are old and weak and have other chronic diseases at the same time, in order to prevent radiation damage, the dose of radiotherapy is generally lower, so the time needed is shorter, for example, radiotherapy for lung cancer combined with chronic bronchitis takes about 5 weeks instead of the conventional 6-7 weeks; in order to prevent growth and development from being affected by the damage caused by radiotherapy for the young, the time needed for radiotherapy is shorter than that for the adults, for example, radiotherapy for children’s lymphoma generally takes 3-4 weeks. 41. Can the same part of tumor be treated with radiation therapy repeatedly? One of the main problems encountered in radiotherapy is that the radiation damage of normal tissues and organs around the tumor limits the radiotherapy dose to the tumor, i.e., while the tumor is being treated, the radiotherapy dose received by normal tissues and organs around the tumor must be controlled within a certain range, so that the normal tissues and organs around the tumor do not suffer from serious radiation damage. For example, the spinal cord can’t receive more than 4000 higory, otherwise it may cause paralysis; the small intestine and stomach can’t exceed 4500 higory, otherwise it may cause ulcer, perforation and bleeding. Moreover, in terms of the tumor tissue itself, the efficacy of radiotherapy is also reduced when re-programming radiotherapy due to the decreased sensitivity of tumor cells to radiotherapy. Therefore, under general circumstances, repeated radiotherapy cannot be applied to one part of the tumor, especially when the interval is too short (e.g. 2-3 months between two courses of radiotherapy), when the tumor is not sensitive to radiotherapy, or when the tumor is in close proximity to organs such as brainstem, spinal cord, kidney, and so on. Of course, if the interval time is long, such as more than one year between two courses of radiotherapy, the physical condition of the tumor patient is good, the normal tissues around the tumor have less damage in the last radiotherapy, or the recovery of the radiotherapy damage is good, and there is no other suitable treatment for the tumor in the same area, then the re-course radiotherapy can be considered as well. However, more serious radiotherapy injuries must be taken into consideration when retreatment radiotherapy is given. For example, retreatment radiotherapy for nasal DI cancer may further aggravate the fibrosis and hardening of the skin in the neck, thus affecting the blood supply of head and face of the patient, and the patient will have obvious facial swelling and even memory loss; it may also cause fibrosis of the soft palate affecting eating; facial fibrosis affecting the opening of the mouth. Therefore, it is necessary to irradiate more than one radiation field when re-programming radiotherapy, and to have the smallest possible radiotherapy range and the lowest possible radiotherapy dose. 42. What are the skin changes in the radiotherapy area and how to deal with them? The earliest manifestation of the skin in the radiotherapy area is erythema of the skin, which appears a few days after radiotherapy, which is the result of vascular reaction after radiotherapy. This is the result of vascular reaction after radiotherapy. With the increase of the number of radiotherapy sessions, the erythema area will be further expanded, and there will be mild swelling, accompanied by itching, and the skin in the radiotherapy area will be darkened by hyperpigmentation, and the skin will be peeled off after about 20 sessions of irradiation, and even ulcers will be formed, but of course, at the same time, the surrounding unirradiated normal skin cells will keep moving into the peeled off and ulcerated area, so as to make it repair and heal continuously. After high dose radiotherapy, the skin in the radiotherapy area will show hyperpigmentation or hypopigmentation with macular changes, and there are changes such as expansion of capillaries and hardening of skin fibrosis. However, due to individual variability, each person’s reaction is not the same. For these reactions, especially when the skin ulcers patients need to pay attention to: the skin should be fully exposed to avoid friction, underwear and collars should be soft, clean, as far as possible, do not wear chemical fiber underwear; can not let the sun and wind blowing; can not use too hot water bath; can not use irritating washing products; not to scratch with their hands, otherwise it will make the ulcerated area become larger and is not easy to heal. Of course, the doctor will do the corresponding treatment in different reaction period, such as redness and swelling can be used some astringent anti-itching drugs such as peppermint starch, hydrogenated oil; and skin peeling ulcers, can be used to promote the healing of the skin of the medication, such as hydrogenated oil, if there is a combination of inflammation, but also can be used for some topical anti-inflammatory drugs, such as erythromycin ointment, and so on. Later skin pigmentation, maculopapular changes do not need to make special treatment, generally irreversible. For the hardening of skin fibrosis, some drugs can be used to soften the knots and activate blood circulation, such as compound danshen tablets, vasculitis tablets, etc., but the effect is also very limited. 43.How to deal with the broken skin and running water in the irradiation area? Irradiation area skin ulceration, running water is radiotherapy to a certain time when the skin occurs more serious radiotherapy reaction, is irradiated by the region of the skin cells are damaged faster than the normal skin cell repair speed results. From the patient’s point of view, we should pay attention to fully expose the broken area, and fluid skin breakout should be more on the same side of the upper limb lifting, so as to fully expose the axillary skin; to reduce the local friction, avoid scratching; underwear to be soft and clean, try to wear cotton underwear and less chemical fiber underwear; to reduce the local stimulation, such as the use of irritating soaps and other toiletries, do not use too hot water to take a bath, can not be exposed to the sun, and so on. Doctors in the treatment to promote skin healing to reduce the inflammatory response and anti-inflammatory treatment when necessary. The medication made in our hospital: Hydrodi oil with hydrocortisone and cod liver oil as the main ingredients, can effectively reduce the inflammatory reaction, stop itching, and can promote skin healing. For the bacterial infection combined with skin breakout, if it is mild and limited, anti-inflammatory ointment can be used externally, such as erythromycin and chloramphenicol ointment; when the infection is heavy, anti-inflammatory drugs can be injected into the muscle or static point of anti-inflammatory drugs. In conclusion, the skin ulceration in irradiated area is a normal radiotherapy reaction, as long as the patient cooperates with the doctor, reasonable treatment can be cured. 44: Why will patients with head and neck tumors have dry mouth after radiotherapy and how to prevent it? Normal people’s saliva is secreted by parotid gland, submandibular gland, sublingual gland, especially parotid gland to keep the mouth moist and help digestion of food, while patients with malignant tumors of head and neck undergo radiotherapy, most of the above glands are in the radiation field. After receiving a high dose of radiotherapy, the glandular cells of the normal glands cannot secrete enough saliva, which becomes little and sticky, so the patient will feel dry mouth. This condition begins during radiation therapy and can last a lifetime. Although there is no good way to normalize the salivary secretion function, the following methods can reduce the symptoms: ① When making the treatment plan, the doctor should avoid irradiation of parotid glands and other glands or excessive irradiation of these glands by all kinds of treatments if they can be avoided, especially when the patient has tongue cancer, gingival cancer, and buccal mucous membrane cancer on one side of the body; ② Apply many kinds of treatment plans, such as radiotherapy and surgery, external radiotherapy and interposition of tissue or implantation of tissue. radiotherapy with intertissue implantation or intracavitary treatment, controlling the dose of radiotherapy for a large area and intensifying the local dose. Even if the damage of the gland is reduced. The tumor can also be well controlled; (3) patients should drink small amount of water many times in the course of treatment and eat more vitamin-rich food and fruits, such as vegetables, pears, watermelon, strawberries, etc.; (4) eat less spicy food and “tonic medicines” (e.g. ginseng, etc.), and avoid smoking and alcohol; (5) pay attention to oral hygiene and gargle; (5) cooperate with the traditional Chinese medicines that can generate fluids and remove the fire, such as Fatty Hai Hai, Maitong, chrysanthemums, and green tea brewing and taking. 45. Patients with head and neck tumors will have white film and ulceration of oral mucosa during radiotherapy, what is the reason for this and how to deal with it? For patients with head and neck tumor, because not only the tumor area receives treatment, but also its corresponding preventive treatment range, generally the oral cavity, pharynx and throat are in the radiation therapy field, so the range of normal tissues is larger. Correspondingly, the reaction to radiotherapy is also larger. When the radiotherapy dose reaches 20～30 Gray, due to acute congestion and edema of oropharyngeal mucosa, patients will feel dry mouth and sore throat, especially when swallowing, and quite a number of patients said “even swallowing saliva is very difficult”. With the increase of radiotherapy dose, some mucous membrane breaks down to form ulcers, and some necrotic material is deposited there to form a white film, which we call “white film”, when the doctor examines, he will find that the oropharynx is congested with blood, erosion, ulceration, and there is a white film, which is usually found in the soft palate, buccal mucous membranes and other parts of the body. At this time, the patient’s reaction is very heavy, and some patients even drip not people. At this time, for the patient should be more gargling, keep the mouth clean, eat more light food, like milk, egg custard, rice porridge, pear water, watermelon juice, etc., avoid spicy food and tobacco and alcohol. For the doctor, you can give the patient oral large doses of vitamin Bz group, C, E, etc., to oral ulcer jelly, ketamine spray throat liquid local anti-inflammatory, can also be taken orally half an hour before the meal dicaine sugar cubes, to reduce hypopharyngeal pain, in order to facilitate eating, but also with the Chinese herb