RADIATION THERAPY

From Big Medical Encyclopedia

RADIATION THERAPY — a method of treatment of various diseases by means of ionizing radiation. Major importance of L. t. has at treatment of malignant new growths. It is based on achievements experimental and a wedge, oncology, radiology, biophysics, radiobiology, physics, etc. For L. t. use electromagnetic radiations (x-ray and gamma radiation), and also corpuscular radiations (electrons, neutrons, protons, deuterons, pi mesons, alpha particles, etc.).

Development of L. t. it is connected with opening in 1895. K. Rentgen of X-beams (see. X-ray emission ), in 1896. A. Bekkerel — natural radioactivity and in 1898 M. Sclodovscoy-Curie and P. Curie — radium (see. Radioactivity ). New opportunities for L. t. there were in connection with opening in 1934 F. Zholio-Curie and I. Zholio-Curie of induced radioactivity, creation of linear and cyclic electronic accelerators, and also particle accelerators of high energy. Scientific and technical progress promoted formation of L. t. as sciences and to transition from empirical medical to evidence-based a wedge, to use ionizing radiation (see).

Various ways and options L. t. have various, quite often traditional and historically developed names — such, e.g., as a shaulterapiya, a curietherapy, a bukkiterapiya.

By the form the used radiation distinguish photon (quantum) and corpuscular L. t. Quantum L. t. carry out x-ray (low-voltage, ortovoltny and megavoltny) and gamma radiation; corpuscular L. t. — alpha, beta radiation, electrons, neutrons, pi mesons, protons. V L. t. apply various ways of radiation differing in features of an arrangement of a source of ionizing radiation and the irradiated object (distant and blizkodistantsionny, superficial, intracavitary, interstitial; the last three ways sometimes call also contact irradiation), a condition of system a source of radiation — the patient (static and mobile radiation), use of special devices for formation of the dozny field (radiation using protective blocks, wedge-shaped filters, through trellised diaphragms). Each of these ways of radiation has many options with various combinations of geometrical, mechanical and physical conditions, e.g. convergent radiation, and also radiation through individually created figured fields, by means of applicators, etc.

Klin, use of L are known tangential, krupnopolny, multifield, rotational (in particular, sector and eccentric). t. depending on indications carry out in the form of direct direct radiation patol, the center or indirect influence on patol, the center by radiation of the central or peripheral parts of the nervous system, hemadens (indirect, indirect L. t.). Under the influence of L. t. some functions of an organism are suppressed, growth of cells and fabrics is oppressed; in some cases in them irreversible changes are caused by damage nucleinic to - t, molecules of protein, enzymes, etc.

A type of radiation, value of an absorbed dose (see. Doses of ionizing radiation ), its distribution in time and space, feature of structure of the irradiated fabric significantly influence character response biol, effect. Also individual is important radio sensitivity (see) various biol, structures. In a wedge, practice use representation about so-called. radiotherapeutic interval (see), i.e. a difference in radio sensitivity patol, and normal fabrics. At a big radiotherapeutic interval patol, the center (e.g., a tumor) has high radio-sensitivity, and its destruction under the influence of ionizing radiation is not followed by rough changes of surrounding fabrics; at a small radiotherapeutic interval patol. the center is radio resistant, i.e. for its damage the high doses of radiation causing also damage to healthy fabrics are required.

For L. t. apply methods single-step, fractional and continuous radiations (see). Use a single-step method of radiation seldom; it consists in single influence in a certain chosen dose of radiation. It is most widespread fractional, or fractioned, a method, at Krom for obtaining necessary therapeutic effect radiation is carried out, as a rule, 5 weekly in a single dose 200 — 250 I am glad to a total dose in several thousands is glad. For fractional radiation also higher doses of radiation with lengthening of intervals between sessions (average and large fractionation) can be used. Apply also the so-called split courses of treatment at which in the middle of a course of fractional radiation appoint a break to 1 — 3 week. The continuous method of radiation is characterized long (within many hours or days) by impact of a radiator on a tumor and the fabrics surrounding it (e.g., at interstitial introduction of a source of ionizing radiation). Choice of a method L. t. is based on a rational combination of such factors as a type of ionizing radiation, time factor of radiation (see), dosage rate of radiation (see), etc.

As a result of radiation the exacerbation of the dozing infection is possible. The exacerbation of tuberculosis arises when patol, the center in a stage of infiltration, disintegration and planting is located in the irradiated volume. Inactive forms of tuberculosis do not interfere with L. t. at preventive purpose of antituberculous remedies. L. t. sometimes is followed by beam reactions or complications (see. Beam damages ), which usually it is possible to minimize or avoid at the correct planning and carrying out radiation. At radiation it is necessary to aim at that vitals, and also eyes, zones of incomplete ossification, a gonad and other closed glands as far as it is possible, were out of direct beam influence. For their protection use special protective agents (see. Antiactinic protection ).

Radiation therapy in oncology

L. t. malignant new growths it is directed to oppression of reproductive ability and destruction of structure of a tumor at the minimum beam damages of healthy fabrics. In the course of L. t. viability decreases and there occurs death of tumor cells, there is an obliteration of small vessels, development of connecting fabric is noted, inflammatory reaction in the tumor and around it disappears that in general leads to reduction of the sizes or elimination of a tumor.

L. t. in oncology appoint according to strictly reasonable indications concerning diseases which diagnosis is, as a rule, confirmed with data morfol, researches. At the same time it can be radical and palliative.

Radical L. t. usually appoint at rather small, limited tumors without metastasises or with existence of single metastasises in limf. nodes. Radical L. t. the proximity of a tumor to vital can interfere or to critical body (see), germination of a tumor in large vessels, weight of the general condition of the patient and existence of associated diseases. As a result of L. t. the tumor can disappear that it is not necessary to identify in all cases with treatment since later a nek-swarm time there can sometimes be recurrence.

At palliative L. t. along with temporary suppression of growth of a tumor and reduction of its volume usually abate, and sometimes pains and inflammatory reaction completely disappear, are normalized fiziol. departures.

The L is important. t. as a component of the combined treatment in a look before - and postoperative radiation. Before radical operation the short course of preirradiation can be appointed, a cut it is carried out during 2 — 5 days by several daily large fractions, for the purpose of damage of the most radio tumor cells and decrease in danger of their dissimination during operation. The prolonged preirradiation is more widespread, a cut it is carried out in the usual mode during 3 — 4 weeks then in 2 — 4 weeks operation is carried out.

The combined treatment with postoperative radiation (sometimes after operation with preoperative L. t.) it is carried out at not radical operations or after removal of high-radio sensitive tumors for the purpose of impact on single tumor cells which could dissipate in fabrics of a surgery field.

Possibility of use of L. t. together with various antineoplastic means it is actively studied, attempts of obtaining the potentiated or summing up antineoplastic effect of ionizing radiation and chemical agents become. At L. t. use the radio sensibilizing substances (see) which are capable to get into hypoxemic sites of a tumor, increasing their damageability due to oxygenation (see. Oxygen effect ). Results radiation in the conditions of supertension of oxygen in similar result. At inhalation of gas mixtures with the small oxygen content radio sensitivity of the healthy, surrounding a tumor fabrics goes down (hypoxyradiotheraphy) and, thus, the radiotherapeutic interval increases. Use of L is based on this principle. t. in the conditions of a local hypoxia, perspectives of the general and local hyperthermia, etc. are studied.

L. t. at treatment of tumoral diseases at children has a number of the features connected with high radio-sensitivity of the growing organism and is most often a component of the combined and complex treatment, e.g. at some new growths of kidneys, nervous and endocrine systems. At radical L. t. in connection with low radio sensitivity of many malignant tumors children have a need for use of high total doses of radiation that creates an adverse radiotherapeutic interval and is the basis for limited independent use of L. t. at the children suffering onkol, diseases.

Radiation therapy of not tumoral diseases

L. t. in small doses it is effective at some not tumoral diseases; it is applied at inflammatory processes (a furuncle, an anthrax, abscess, phlegmon, a hydradenitis, mastitis, an erysipelatous inflammation, a felon, osteomyelitis, a paraproctitis, etc.), postoperative inflammatory infiltrates and fistulas, to treatment of a wound fever, burns, diseases of a musculoskeletal system (arthrosis, arthritis, a chondrosis, a bursitis, an epicondylitis, etc.), some diseases of a nervous system (neuritis, neuralgia, a plexitis, radiculitis, an arachnoiditis, a kauzalgiya, stump neuralgias, a myelosyringosis) and skin (a pruritic dermatosis, eczema, etc.). It can be applied to treatment of patients with an actinomycosis, at some endocrine diseases, e.g. a thyrotoxicosis.

Lech. effect of L. t. not tumoral diseases the hl is connected. obr. with the desensibilizing, antiinflammatory, anesthetizing and anti-spastic action of ionizing radiation. In the irradiated fabrics at the same time changes of function of reticuloendothelial system, krovo-and lymphokineses, fabric exchange, acid-base equilibrium, permeability of vessels, etc. are noted. Single absorbed doses at L. t. not tumoral diseases can fluctuate from 15 to 75 I am glad, and total — from 75 to 500 I am glad; there are observations of satisfactory results of radiation during the use of such low single doses as 3 — 5 I am glad. At acute inflammatory processes and in an initial stage of diseases radiation is carried out at an interval of 3 — 5 days whereas at hron, the course of a disease and in late stages patol, process intervals between sessions of radiation are reduced to 1 — 2 days, and radiation is carried out in higher doses. The volume of the irradiated fabrics shall exceed, as a rule, clinically determined sizes patol, the center since favorable result of L. t. it is connected as well with reaction of surrounding fabrics. The targets located superficially and in soft tissues irradiate with low-energy radiations in smaller doses, than a target of deeper localization and in dense fabrics, napr, in bones. In these cases use rather high doses and high-energy radiations.

Contraindications to L. t. — anemia, lymphocytopenia, leykotsitopeniya and thrombocytopenia, feverish condition, cardiovascular and respiratory insufficiency, diseases of kidneys, diseases of c. N page, a cachexia, a preperforative state and perforation of the bodies affected with a tumor, existence in the area of allergic manifestations which is subject to radiation, etc.

Sources of ionizing radiation and devices for radiation therapy

At L. t. use sources with radioactive nuclides (see. Isotopes ) and generators of ionizing radiation. Sources with radioactive nuclides apply to alpha, beta, gamma and neutron therapy in the conditions of remote, intracavitary and interstitial radiation. Generators of ionizing radiation, to the Crimea belong the roentgenotherapeutic device (see. X-ray apparatus ), various particle accelerators (see) and generators of neutrons, use for remote and contact irradiation.

Sources of ionizing radiation are subdivided on closed and opened. The closed sources have the non-radioactive tight cover or a covering, a cut excludes a possibility of transition of a radioactive nuclide to the environment. The closed sources have an appearance of cylinders, needles, granules, beads, etc. (see. Radioactive drugs ). Open sources of ionizing radiation have no the isolating covering and can come into direct contact with the environment; they are applied in the form of solutions, colloids, powders, suspensions.

Suitability of a radioactive nuclide for L. t. is defined by a type of radiation, its energy, half-life and technical capability of production of the sources conforming to medical requirements. Sources of ionizing radiation store in special rooms in the protective containers and safes providing requirements of radiation safety. All types of works with radioactive sources: their movement from storage and back, sterilization, preparation for use (cultivation of solutions, filling of syringes, charging of special guns with granules, etc.), carry out imposing of sources on a surface or introduction to a perigastrium and all process of radiation in specially equipped rooms with use radiological zashchitnotekhnologichesky equipment (see), radiological tools (see), individual protective accessories (dressing gowns, aprons, gloves, masks, screens, screens, etc.) and devices of control of radiation safety (see. Dosimetry of ionizing radiation, dosimeters ). The radio surgeries connected with introduction of radioactive sources in a cavity and tissue of a body of the patient carry out with observance of the general surgical requirements, rules of an asepsis and antiseptics. For contact irradiation manufacture individual applicators in which have and fix the closed sources according to a form and the sizes of a target.

X-ray apparatus with tension of generation of radiation to 100 kV apply to superficial and intracavitary radiation, and devices with tension of generation of radiation to 250 kV generally use for L. t. not tumoral diseases.

In gamma and therapeutic devices (see. Gamma devices ) apply the closed sources of high activity with nuclides of cobalt-60, caesium-137, iridium-192 to remote and intracavitary radiation. Sources of ionizing radiation have a limited period of validity, dependent hl. obr. from half-life of a nuclide in this connection the gamma and therapeutic device is periodically recharged new sources of nominal activity.

Among electronic accelerators the most perspective consider the linear accelerator. For L. t. heavy charged particles use accelerators of physical research institutes.

See also Alpha therapy , Beta-ray therapy , Gamma therapy , Neutron therapy , Proton therapy , Roentgenotherapy , Electronic therapy .


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A.S. Pavlov, A. I. Ruderman; M. Sh. Weinberg (tekhn.).

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