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Radiation therapy

Radiation therapy (radiotherapy) is a treatment with ionizing radiation. It is mainly used to affect tumors in order to cure a patient (radical radiation therapy) or temporary relief of his condition (palliative radiation therapy). Radiation therapy can be used for some non-neoplastic diseases (inflammatory, processes such as mastitis, panaritium , hydradenitis, etc., eczema, neurodermatitis, etc.) in cases where other treatment methods have been unsuccessful.

Sources of ionizing radiation are radioactive isotopes (see), used in the form of specially manufactured preparations (see Radioactive preparations ), or radiation generated by devices (see X-ray machines . Gamma devices , Accelerators of charged particles ). Natural radioactive elements ( radium , radium-mesotory) are currently no longer used for therapy (radium therapy).

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The basis of radiation therapy of tumor diseases is a pattern known in radiobiology , indicating the unequal radiosensitivity (see) of healthy and tumor tissues. By virtue of, as a rule, greater radiosensitivity, the tumors, upon exposure to radiation, are damaged more strongly than the surrounding healthy tissues, which inevitably fall into the irradiation zone. The longer the radiosensitivity interval of healthy and tumor tissues (therapeutic interval), the easier it is to destroy a tumor by irradiation, without causing significant harm to healthy surrounding tissues. Naturally, high radiosensitivity tumors extend the therapeutic range. A therapeutic interval sufficient for treatment usually occurs in cervical cancer, tumors of the mammary gland , tonsils, pharynx, nasopharynx, larynx, and some other organs. Radiation therapy can be used as an independent method of treatment (for example, for tumors of the nasopharynx, lip cancer, etc.). Most often, radiation therapy is carried out in combination with a surgical treatment method or chemotherapy (combined radiation therapy). With combined radiation and surgical treatment methods, radiation therapy can be used both in preoperative (preoperative radiation therapy) and postoperative (postoperative, or prophylactic, radiation therapy) periods. Tumor irradiation is carried out mainly to suppress its activity; in cases where it is not possible to remove the tumor while preserving the principle of ablastics (see), the main goal of radiation therapy is an attempt to bring the patient into an operable condition. When conducting pre- and postoperative radiation therapy, not only the tumor or its container is exposed to radiation, but also areas of possible metastasis. For example, in breast cancer, the axillary cavities, supraclavicular and subclavicular regions, and the mediastinum are also irradiated.

There are the following methods of radiation therapy: application, internal, intracavitary, interstitial, remote.

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Applied radiation therapy - treatment with β- or γ-active drugs, located on special applicators that keep radioactive sources in a certain place and at the required distance from the surface of the body. It is used to treat diseases of the skin or mucous membranes. Dummy applicators that were previously used very widely are rarely used now. The most commonly used are so-called flexible β applicators intended for the treatment of superficial diseases - eczema , neurodermatitis, capillary hemangiomas , etc. They are made in the form of a flexible plastic plate containing uniformly distributed radioactive phosphorus , thallium or strontium , which is superimposed on the affected skin for a few minutes or even hours. When working with β-applicators, it is necessary to carefully monitor the safety of the plastic bag in which the applicator is located, since otherwise the patient’s skin may be contaminated with dust particles of radioactive drugs.

Internal radiation therapy is carried out by introducing into the body (per os or directly into the blood stream) radioactive drugs - more often I 131 (see Iodine, radioactive), P 32 (see Phosphorus, radioactive ), Au 148 (see Gold, radioactive) . It is used in diseases of the thyroid gland , blood diseases (for example, polycythemia , leukemia), lymphogranulomatosis. Patients receiving radioactive drugs inside, require isolation in special wards; their urine and feces within 10 days after taking the drug is collected in special containers (see. Radioisotope containers).

Intracavitary radiotherapy is the irradiation of tumors of the abdominal organs by applying radioactive preparations to them, most often cobalt-60 (see Cobalt, radioactive). Most often used in the treatment of cancer of the cervix and uterus, vagina , bladder, rectum , esophagus and nasopharynx. Drugs administered for several hours or even a day. Introduction is carried out only in specially equipped rooms - radio manipulation. With the introduction of drugs staff is behind a special lead screens.

Patients with radioactive drugs are contained in special wards (see Radiology Department). A special feature of patient care for whom treatment is performed is the close monitoring and prevention of drug release. After removing the drugs, patients can be in the general wards.

Interstitial radiation therapy - irradiation of tumors by inserting radioactive cobalt needles into them or flashing a tumor with nylon threads filled with thin wire segments made of radioactive cobalt, gold or iridium. Most often used for superficial tumors, as well as tumors of the tongue and oral cavity. Radioactive needles and threads are injected for several days, and then removed. Recently, instead of needles and threads, colloidal solutions of radioactive gold-198 or very small iridium grains are injected into the tumor by injection. The introduction of the grains is carried out using a special pistol, and colloidal solutions using syringes in lead protective cases (see Radiological instruments).

Remote radiation therapy - radiation with the help of special facilities that generate ionizing radiation, and the radiation source is located at some distance from the patient. The radiation source can be an X-ray unit - roentgenotherapy ; radioactive cobalt or cesium - telegrammatherapy; betatron or linear accelerator - megavolt therapy. Depending on what type of radiation the betatron uses - electronic (see Electronic radiation) or bremsstrahlung, they distinguish between megavolt therapy, electron or bremsstrahlung. Remote radiation therapy is the most common type of radiation therapy. It is carried out only in special treatment rooms, where radiation sources are installed permanently (see Gamma devices). When using devices "Beam" and "Rokus", characterized by good protection of the radiation source, the risk of exposure to personnel is very small.

Radiation therapy [synonym: cyuritherapy, radium therapy, radiotherapy (outdated names)] is a method of treating diseases with the help of various types of ionizing radiation of various energies.

As a clinical discipline, radiation therapy is closely associated with radiobiology (see), radiation physics to dosimetry (see), as well as with the technique of therapeutic use of radiation sources; Its main sections are methods for the therapeutic use of radiation and a radiological clinic.

Radiation therapy combines the therapeutic use of X-ray, gamma, electron, proton, neutron and other ionizing radiation (see Alpha-therapy, Beta-therapy, Gamma-therapy, Neutron therapy, Proton therapy, X-ray therapy, Electronic therapy).

The rational organization of radiation therapy provides for the concentration of various types of it within the framework of large centralized hospital (clinical) institutions.

Radiation therapy should be comprehensive; the success of treatment depends on it. Radiation therapy is carried out with the friendly work of radiologists and medical physicists who are jointly solving fundamental and particular clinical problems of optimal radiation exposure.

The tasks of radiation therapy: 1) dosimetric characteristics of radiation, assessment of dose fields created in lesions and healthy tissues; 2) radiobiological substantiation of radiation exposure, characteristic of tissue radiosensitivity, directional change of radiosensitivity; 3) elucidation of the reactions of healthy and pathological tissues and the whole organism to irradiation, the development of methods and tactics of irradiations, the fight against immediate and late complications.