What is radiotherapy?
Radiation therapy refers to the use of radioactive isotopes, ordinary X-rays from X-ray machines, high-energy X-rays from gas pedals, and electron beams, protons, fast neutrons, negative neutrons and other heavy particles from various gas pedals to treat cancerous tumors.
Radiation therapy in a broad sense includes both radiation therapy for tumors in radiotherapy departments and internal isotope therapy in nuclear medicine departments (e.g. 131 iodine for thyroid cancer and hyperthyroidism, 32 phosphorus for cancerous pleural fluid, etc.). Radiation therapy in a narrow sense generally refers to the former only, i.e. what people generally call tumor radiation therapy. There are two types of radiation therapy: one is long-distance radiation therapy (external radiation), which means that the radiation source is irradiated at a certain distance from the patient’s body, and the radiation penetrates into the body from the patient’s body surface to a certain depth to achieve the purpose of treating tumor, and the other is brachytherapy (internal radiation), which means that the radiation source is sealed inside the tumor or on the surface of the tumor, such as into the natural cavity of the human body (e.g. tongue, tissues, etc.). The other type of radiation therapy is brachytherapy (internal irradiation), in which the radiation source is placed inside the tumor or on the surface of the tumor, such as inside the natural cavity of the body or inside the tissues (such as the tongue, nose, pharynx, esophagus, trachea and uterine body) for irradiation, i.e., intracavity, intertissue insertion and model dressing. In recent years, with the continuous improvement of medical equipment in each hospital, brachytherapy has also gradually become popular.
There are three basic differences between in vivo and external radiation therapy.
① Compared with external irradiation, the intensity of radiation source for internal irradiation is smaller, from a few milli-curie to about 100 milli-curie, and the treatment distance is shorter;
②In external irradiation, most of the radiation energy is shielded by collimators, beam limiters, etc., and only a small portion of the energy reaches the tissue; in internal irradiation, on the contrary, most of the energy is absorbed by the tissue;
③In vitro irradiation, the radiation must pass through the skin and normal tissues to reach the tumor, the tumor dose is limited by the tolerance of the skin and normal tissues, and in order to get a high and uniform tumor dose, it is necessary to select different energy rays and adopt multi-wild irradiation techniques, etc.; while in vivo irradiation, the rays reach the tumor tissues, and the deeper normal tissues are little irradiated.
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 to treat tumors.
Because after the normal tissues are damaged by radiation, the automatic stability control system starts to work, the cell proliferation cycle is shortened and the growth ratio of cells increases, so that the repair of the damaged normal tissues is completed quickly. In contrast, the tumor cell population has its own, different response system from normal tissue after being struck by radiation, and the response is extremely different between different tumors. During the observation of human tumor cells, it is found that there is a clear relationship between cell proliferation rate, cell loss and radiosensitivity. It requires higher doses to be effective. Since normal tissues have automatic stability control system and tumor tissues are different, the recovery and growth of normal and tumor tissues after fractionated irradiation are different.
(1) After irradiation, the normal tissue has a fast return to normal cell proliferation cycle, while the tumor tissue is slow to repair the radiation damage and the cell proliferation cycle is prolonged;
② Although tumors may have temporary accelerated growth after irradiation, this growth rate is not as fast as the proliferation of normal tissues to repair the damage;
(3) The growth rate of tumor cell population is larger than that of normal tissues, and more cells are in the cell cycle, so more cells are damaged by lethal injury than normal tissues, and more cells are damaged by different degrees than normal tissues.
Therefore, in clinical radiotherapy for tumor, the difference in radiotherapy effect between normal tissues and tumor tissues is used to carry out fractionated radiotherapy to achieve the purpose of killing tumor cells and protecting normal tissues as much as possible. In the clinical treatment of tumor, about 70% or more of tumor patients have received radiation therapy, including radical radiotherapy and palliative radiotherapy.
What is a gas pedal?
A gas pedal is a device or equipment that artificially uses the force of electric and magnetic fields to accelerate charged particles to high energy. Gas pedals can produce both high-energy electron beams, high-energy X-rays and fast neutrons in the energy range of 4 to 50 MeV.
What kinds of gas pedals are commonly used in radiotherapy and what are their characteristics?
The following three types of gas pedals are commonly used in radiotherapy: electron induction gas pedal, electron linear gas pedal and electron cyclotron. The characteristics are as follows: The advantage of electron induction gas pedals is that they are technically simple, cheap to manufacture, and easy to achieve high energies such as 25 MeV. Its generated electron lines, the output is large enough, the energy adjustable range is wide. The disadvantage is that the X-ray output is relatively low, and the irradiation field is also small. At the same time, this equipment is large, heavy, to the installation and medical treatment bring some difficulties. The advantage of the electron linear gas pedal is to overcome the above disadvantages, it has a high enough output for both electrons and X-rays, which has the potential to expand the irradiation field, and can use the deflection system to do isocentric treatment. The disadvantage is that the structure is complex, the cost is expensive, and the maintenance requirements are high. The electron cyclotron has both the economy of an electron induction gas pedal and the high output of a linear gas pedal, and its electron and X-ray energy are ideal for medical use. In short, it is a simple structure, small size, low cost, is the development direction of linear gas pedal.
What is an electron linear gas pedal?
The electron linear gas pedal is a radiation therapy device developed in the 1970’s. About 70% of all cancers can be treated with the gas pedal with good results. The linear gas pedal can produce X-rays with a wide range of energy and can produce high-energy electron beams of various energies. The radiation dose of X-rays is high, the field area is large, the radiation homogeneity is good, the focus of the radiation source is small, the accuracy is high, and the safety for patients is good. For example, when using high-energy electron beam to irradiate malignant tumors such as parotid gland and submandibular gland cancer that are confined to one side, the tongue and contralateral oral mucosa can be protected from damage. Whole body irradiation for skin cancer also has satisfactory efficacy. High-energy electron beam can also be used for intraoperative irradiation, for mid- to late-stage tumors and tumors that are not easily removed surgically, and for a single high-dose irradiation when the tumor is removed surgically. Because of the exposure irradiation, accurate positioning, and accurate irradiation range, it can receive effects that cannot be received by surgery alone or by external irradiation alone. High-energy X-rays can be used to irradiate the tumor for treatment before surgery, so that the tumor shrinks and the adhesions are loosened, thus increasing the resection rate of surgery, so that active tumor cells are killed or resisted, thus reducing cancer metastasis due to surgical operation and improving the survival rate of patients. For advanced deep cancer that has lost the chance of radical radiotherapy, it can be used as palliative radiotherapy, which can provide pain relief, improve the quality of survival and even prolong life.
BJ-14 medical standing wave electron linear gas pedal
BJ-14 medical standing wave electron linear gas pedal is a kind of medium energy medical gas pedal which can carry out both X-ray treatment and electron treatment. It won the second prize of Beijing Science and Technology Progress in 1999.
Main features.
Double photon (X-radiation) energy in accordance with Chinese characteristics, which can realize X-radiation treatment with arbitrary energy of 6MV, 8MV and 10MV.
With multi-grade electron radiation, the highest energy can reach 14 MeV. asymmetric radiation can be formed relative to the center of rotation of the radiation head to meet the needs of special radiotherapy.
With computerized automatic control system, software control is powerful and easy to use, and can assist engineering and physics personnel to complete most of the daily maintenance and calibration work.
Automatic wedge irradiation function, which can realize any angle from 0° to 60°.
Perfect automatic arc treatment function, especially suitable for use with X-blade.
GWXJ80 cobalt 60 teletherapy machine adopts asymmetric opening and closing independent collimator system design, microcomputer control management, equipped with advanced case management system, with superior performance, not only for conventional fixed beam treatment, and can perform isocentric moving beam treatment (rotation treatment, swing treatment, jump treatment). With complete functions, high accuracy of movement, smooth operation and high degree of automation, it is widely used in external radiation therapy for tumors.
What is 60 cobalt therapy machine and what are its advantages and disadvantages?
60 cobalt therapy machine is commonly called “cobalt gun”, 60 cobalt is a kind of artificially produced radionuclide. Cobalt gun” is a device that uses 60 cobalt as the radiation source, kills cancer cells with gamma rays and treats tumors. 60 cobalt machine consists of the following parts: a sealed radiation source; a source container and a protective head; a line shield device with a switch; a beam limiting cylinder with a directional beam limiting, a mechanical system to support the head and its attached equipment and a control panel). Its advantages are.
(1) High penetrating power of the rays i.e., it can treat tumors of considerable depth.
(2) Protection of the skin 60 cobalt rays have the greatest energy absorption at 4~5 mm under the skin, and the epidermal dose is relatively small.
(3) Equal absorbed dose for bone and soft tissue That is, when the rays pass through, the absorption of the rays by bone and soft tissue is basically the same, unlike ordinary X-rays, where the bone absorbs more than the soft group and causes more harm to the bone.
(4) Small bypass scattering Protects normal tissues outside the periphery.
(5) Economical, reliable, simple structure and easy maintenance.
Disadvantages are.
(1) Single 60 cobalt energy. (while gas pedals can have a variety of energy X-rays and electrons).
(2) 60 cobalt depth dose is low, in order to increase the dose at depth, the external exposure dose must be increased, resulting in an increase in the whole body exposure. The gas pedal depth dose is high, and the whole-body exposure is low.
(3)60 cobalt has a short half-life (about 5.3 years), and the radioactive source needs to be replaced regularly.
(4)60 cobalt is a radionuclide, with constant radiation release, complex protection and high dose for staff.
(5) 60 cobalt has the problem of penumbra, so that the normal tissue in the field is affected by a certain dose. In short, the low cost and easy maintenance of cobalt machine make it develop faster than other radiotherapy equipment, and it is still the main equipment of radiotherapy.
Radiation therapy simulator
Radiotherapy simulator is a kind of X-ray machine that is used to complete X-ray simulation examination and positioning under the guidance of high-definition X-ray TV system. Before radiotherapy, it is the first guarantee for patients to obtain accurate radiotherapy by calibrating and positioning the tumor to formulate and verify the treatment plan. The HMD–ⅠA curved-arm radiation therapy simulator introduced by our hospital adopts LCD touch screen terminal control, operation and display, with clear image and high positioning accuracy, and the image workstation can realize real-time image acquisition, sharpening, magnification, reduction, multi-frame monitoring, storage and other processing, and realize large-capacity filmless patient file management. Define the field or asymmetric opening and closing and symmetric opening and closing, and has a variety of safety measures, automatic solution of anti-touch function.
What is a deep X-ray machine and under what circumstances is it suitable for use?
A deep X-ray machine is usually an X-ray machine with a tube voltage between 180 and 400 kV. This machine has the same structure and X-ray generation principle as a contact treatment machine. However, since the tube voltage of this machine is higher than that of the contact therapy machine, the intensity and penetration ability of the X-rays produced are greater, so it is mostly used for the treatment of benign diseases and malignant tumors located more superficially. Therefore, it can be used as an adjunct to 60 cobalt treatment machine and gas pedal high-energy X-ray treatment to supplement the dose in superficial areas. According to the needs of treatment, the treatment machine can be designed into three types: fixed irradiation type, swing irradiation type and rotating irradiation type, which makes the application of deep X-ray therapy machine more extensive.
The deep X-ray therapy machine is commonly used for the treatment of benign diseases such as skin scar, axillary odor, neurodermatitis, corns, deeper parts of hemangioma and penile cavernous sclerosis with more ideal effect. It also achieves obvious efficacy for the supplemental radiotherapy of skin cancer, skin adnexal cancer and metastatic cancer of lymph nodes in the neck. The pain-relieving radiotherapy for bone metastases in shallower areas (such as rib or clavicle metastases) is more effective because the photoelectric effect of X-rays in this energy segment is larger and the X-money absorption of bone is higher. Because of the low energy of this treatment machine and the low dose in the deep part of the tissue, it 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 more superficial parts. In many areas of China, this machine is still widely used as a supplement to 60 cobalt treatment machine and gas pedal treatment.
Post-loading machine
The GJD14 remote-controlled radiation therapy machine uses iridium-192 as the radiation source to complete high-dose brachytherapy for common tumors such as esophageal cancer, cervical cancer, nasopharyngeal cancer, rectal cancer, skin cancer and bladder cancer by means of intracavitary, intracanal, insertional implantation, intraoperative and dressing. The rear-loader planning system and treatment system are both computer-controlled, which can precisely formulate radiotherapy plan and determine the best dose distribution.
What is intracavitary radiotherapy and what tumors can it treat?
Intracavitary therapy is a type of brachytherapy that uses the body’s own cavities and tubes to place treatment tubes. Intracavitary therapy is usually performed by placing a 1.7-2.0 mm diameter plastic tube in the treatment area through an endoscope or according to the anatomical site, and then treating it according to the corresponding steps. It can treat nasopharyngeal cancer, esophageal cancer, tracheal cancer, bronchial cancer, rectal cancer, cervical cancer, etc.
What is brachytherapy?
Brachytherapy is to place the radiation source applicator on the surface of the tumor in the human cavity or insert it into the tumor with a needle, and through the computer control system, the radiation source is directly applied to the surface of the tumor or inside the tumor for radiotherapy. At the beginning of this century, the medical staff used to manually place the radiation source on the tumor during brachytherapy, which was subjected to a large amount of radiation. In the 1950s, due to the unfolding of post-loading technology, the staff operated and positioned the radiation source without radiation, which greatly reduced the amount of staff subjected to and improved the accuracy of treatment. It includes five types of intracavitary, intraductal and intertissue insertion, intraoperative placement and model dressing.
What are the types of brachytherapy and what are the advantages and disadvantages of each?
There are two main types of brachytherapy. By dose rate, low dose rate is less than 2Gy per hour and high dose rate is more than 12Gy per hour. The characteristics of low dose rate brachytherapy are: the treatment time takes 37 hours to 3 days after placing the radiation source; less damage to normal tissues; and good efficacy in the treatment of gynecological cancer. Disadvantages.
①The nursing staff is exposed to large amount of radiation;
②Since the source is placed for a long time, the position of the applicator can be easily changed;
③The low dose rate radiation source cannot be miniaturized.
High dose rate proximity afterloading features.
①Short treatment time without hospitalization;
② accurate positioning;
③The 192 iridium radiation source used can be miniaturized (can be used for endotracheal, insertion implants, etc.) for a wide range of treatment uses.
Disadvantages.
① larger damage to normal tissue;
②Heavy local reaction.
Almost all of the current domestic brachytherapy is a high dose rate type.