BETA-RAY THERAPY — one of methods of radiation therapy consisting in radiation of the pathological center β-particles of radioisotopes. B. - t. it has to be ranked as the category of electronic therapy since β-particles and electrons on the essence are identical. Therapeutic effect of B. - t. is based on development of a biological response in the pathological fabrics irradiated with β-particles, the cut is the cornerstone death or loss of ability of separate cells to division. As a source of radiation for B.'s carrying out - t. the numerous radioisotopes undergoing β-disintegration are used. The choice of isotopes depends as from their physical. and chemical parameters, and from a route of administration. B.'s origin - t. it is connected with discovery of induced radioactivity therefore receiving various β-radiating radioisotopes became possible.
The first publications about a possibility of use of artificial radioisotopes in medicine belong to the end of the 30th years. However the begun World War II for a long time detained use of nuclear energy in the peace purposes. In the late forties and the beginning of the 50th years in the USSR the mass production of radiotherapeutic drugs was begun, many of which are successfully used and now.
Depending on a way of the annex of a source of β-radiation to the pathological center distinguish application, intracavitary and interstitial B. - t., which shall be carried out in the conditions of respect for radiation safety.
Application beta therapy
Application beta therapy is performed by the appendix to patholologically to the changed surface of skin or a mucous membrane of the β-applicator.......... The last represents the plate made of a number of plastic or organic materials with inclusion in their composition of the radioisotopes undergoing β-disintegration. The materials used for production of the β-applicator, shall have sufficient plasticity in order that the working surface of the applicator densely adjoined to a surface of the struck center. At the same time these materials shall promote uniform distribution of radioactive connections in them, strongly hold them in the structure and not lose under the influence of radiation of some qualities (durability, plasticity and so forth). As such materials apply polymers (teflon, lucite, polyethylene, polyvinylchloride, polystyrene), ion-exchange substances, filter paper and so forth.
At production of the applicator it is necessary to consider that the form of the last shall repeat a contour of an affected area of skin or mucous membrane and take a healthy surface on 0,3 — 0,5 cm. For radiation of area of an eye the applicator is given the spherical shape corresponding to camber of an eyeglobe. For the purpose of the prevention of possible radiocontamination of skin of the patient the surface of the applicator in addition becomes covered by a thin coat of a polyethylene film. Such precautionary measures are especially necessary in cases of use of long-living radioisotopes.
The choice of radioisotope as a source of β-radiation is defined by energy of β-particles and half-life of isotope. Penetration of β-particles depends on the size of their energy (e.g., β-radiation with energy 1 — 2 Mei provides radiation of the center at a depth respectively 0,5 — 1 cm). Because application B. - t. it is applied preferential at rather superficial defeats, the choice of isotope with energy of β-radiation 111111111 1 — 2 Mei is reasonable.
The following isotopes are applied to production of applicators on power indicators: 32 P, 114 Ce, 90 Sr — 90 Υ, etc.
Duration of a course of application B. - t. depends on the nature of pathological process and it is carried out fractionally during of 1 week up to 1 month. This circumstance causes the choice of isotopes with various half-lives — of several weeks ( 32 P — 14,3 days) up to several years ( 90 Sr — 28,5 years). Applicators with long-living isotopes are suitable for the repeated use.
Dosage rate of the applicator depends on activity of the isotope distributed on unit of its surface, average size of energy of β-particles, thickness of a protective film and so forth. Power of the applicator either is calculated mathematically, or is measured experimentally. The size of a total dose at B.'s carrying out - t. reaches 100 — 500 I am glad (at not tumoral diseases) and 3000 — 6000 I am glad (at new growths).
The indication for application B.'s use - t. superficial forms of a carcinoma cutaneum, capillary hemangiomas, Bowen's disease, giperkeratoza, leukoplakias, limited neurodermatitises, tumoral defeats of a cornea and sclera of eyes, etc. serve. In recent years the tendency to restriction of use of B. - t was outlined. at not tumoral defeats because of risk of cancerogenic action of ionizing radiation.
Application B. - t. it is carried out in the conditions of a hospital and it is out-patient.
The intracavitary beta-ray therapy
the Intracavitary beta-ray therapy is carried out by administration of solution of radioisotopes in a perigastrium. Radioisotopes ( 90 Y, 32 P, 198 Au, etc.) are used in the form of colloidal solutions. The colloid form of drug warns a possibility of its bystry absorption and by that provides long radiation of a surface of the corresponding cavity. At the choice of β-radiation of a source preference is given to isotopes with high energy of β-particles and rather short half-life (from 2 days to 2 weeks) that allows to reach almost full disintegration of isotope in a perigastrium during a course of treatment.
Intracavitary B. - t. finds application at metastatic damages of a pleura and a peritoneum, papillomas of a bladder, and also for the purpose of the prevention of development of implantation metastasises after surgeries concerning cancer of a lung, a stomach, ovaries and so forth.
At metastatic pleurisy and ascites the puncture of the corresponding cavity and evacuation of liquid with the subsequent introduction to a cavity of sterile colloidal solution of radioisotopes of 10 — 20 ml is made. In some cases similar manipulations it is required to repeat two — three times for achievement of lasting effect.
At intracavitary B.'s carrying out - t. for the purpose of prevention of implantation metastasises colloidal solutions enter on 2 — the 5th days after operation through drainage tubes. For single introduction colloids of yttrium or gold with the general activity 100 — 150 mkyur or phosphorus with activity 10 — 15 mkyur are used. Calculation of an absorbed dose is made in the mathematical way.
For treatment of a papillomatosis of a bladder solution of radioisotopes is entered into a cavity of a bubble through the catheter supplied with a rubber bulb for the term of 2 — 3 hours with the subsequent evacuation.
Interstitial beta therapy
Interstitial beta therapy is based on infiltration of fabric of a tumor by solution of any short-lived β-radiating radioisotope or implantation in a tumor of the resolving threads, films or granules, impregnirovanny isotopes. Due to the features of the dozny field high values of a gradient of dosage rate on border of a tumor with normal fabrics are created. This circumstance allows to reduce to a minimum a harmful radiation effect on the fabrics surrounding a tumor. Colloidal solutions of chromic orthophosphate, a tsirkonilfosfat, a suspension of chromic orthophosphate are applied to infiltration of a tumor (active on 32 P), colloidal radioactive solutions of yttrium fluoride ( 90 Υ), gold ( 198 Au) and the gold covered with inactive silver. For production of the resolving materials and granules isotopes are used 90 Y and 32 P. The colloid form of drug promotes long stay it on site injections; during this time there occurs almost full disintegration of isotope.
Important feature of a way of interstitial B. - t. need of careful hypodispersion of drug for an array of a tumor because otherwise certain sites of a tumor will appear out of incidence of β-radiation is.......... The inhomogeneity of the dozny field resulting from uneven distribution of radioactive solution is partially leveled due to high energy of the β-particles having big penetration.
Calculation of a dose for infiltration of radioactive solutions is made on a formula:
Дβ = 73,8 • Co • E • T ef I am glad
where Co — concentration of isotope in fabric (mkkyuri/g), E — mean energy of β-particles, T ef — effective period.
Interstitial B. - t. it is shown at melanomas, the differentiated carcinomas, fibrosarcomas and so forth. Implantation of granules with 90 Υ it is used for a beam hypophysectomy.
The group of techniques of interstitial therapy joins also the options of radiation therapy based on ability of some bodies and fabrics to selectively absorb a number of chemical radioactive connections after their peroral or intravenous administration. So, 131 I selectively concentrates tissue of a thyroid gland; B. - t is based on this principle. with the help 131 I hyper thyrotoxicosis and cancer of a thyroid gland; 32 P is used for treatment of an Osler's disease.
Intracavitary and interstitial B. - t. it is carried out in a hospital on condition of systematic overseeing by a condition of peripheral blood.
Bibliography: Domshlak M. P. Sketches of clinical radiology, M., 1960; Pavlov A. S. Interstitial gamma and beta therapy of malignant tumors, M., 1967; Knotty L. S. and B. V Tickets. Use of radioactive colloid gold (Au 198 ) at treatment of pseudomyxomas of an abdominal cavity, Owls. medical, No. 4, page 33, 1965; Therapeutic use of radioisotopes, the lane with English, under the editorship of M. N. Foteeva, page 49, 251, M., 1952; Silver S. Radioactive nuclides in medicine and biology, Philadelphia, 1968.