dosagerate of RADIATION, biological effect

From Big Medical Encyclopedia

DOSAGE RATE OF RADIATION — the increment of an ionizing radiation dose carried to a unit of time for to-ruyu this increase occurred. M of and. (P) calculate on a formula:

P = dD/dt

where dD — an increment of an ionizing radiation dose, dt — the time term, during to-rogo it occurs.

Power of an air and absorbed dose of radiation is expressed respectively in X-rays and childbirth or multiple to them units carried to units of time (r / sec., r / mines, I am glad / sec., mrad / sec., mkrad / sec., I am glad / mines etc.). According to the International System of Units (SI) the power of an absorbed dose of radiation is expressed in Gr / with (heat in a second), the power of an equivalent dose of radiation — in Stars / with (sievert a second).

Numerous experimental and the wedge, data demonstrate that M.'s change by and. is followed by changes in biol, effect that the gigabyte is considered in practice. rationing, at assessment of radiation hazard, and also during the planning and performing radiation therapy.

Main pattern of influence of M. of and. on biol, reactions it is shown in reduction biol, effect at M.'s decrease of and. from hundreds to shares min. is glad/. In M.'s range of and. from units to shares I am glad / its min. reduction causes falloff biol, effect, in M.'s range of and. from hundreds to tens I am glad / min. — only its insignificant decrease. Nek-roye reduction biol, effect perhaps in process of M.'s increase by and. to thousands I am glad / mines and at powerful pulse influences.

Range of absolute values of M. of and., in Krom there is an essential change of effect in comparison with that at acute exposition, is ambiguous during the use different biol, objects and various criteria for evaluation of defeat.

Reduction biol, effect at M.'s decrease of and. comes to light, e.g., at radiation of microorganisms of yeast, plants, insects, cultures of fabrics. In an experiment on a lab. animals at a certain reduction of M. of and. the dose of so-called half survival can increase in nek-ry cases more than twice. Critical value M. of and., below to-rogo the striking action of ionizing radiation begins to decrease significantly, it is displaced towards reduction for those biol, types, the Crimea svoystven low rate of recovery processes.

M.'s influence by and. affects the size of the ionizing radiation dose causing, e.g., beam reaction of skin, a nervous system, the hemopoietic bodies, etc. M.'s reduction by and. leads to less expressed decrease in indicators immunol, reactivity of an organism, to smaller change biochemical, the indicators characterizing extent of destructive changes after radiation. At M.'s decrease of and. from thousands to units I am glad / mines the protective effect of a hypoxia decreases, and at smaller M. of and. the hypoxia does not affect results of impact of ionizing radiation.

Degree of distinctions in reaction of separate body tissues to M.'s change by and. in certain limits it is connected with speed them fiziol, regenerations. At M.'s reduction by and. and, therefore, lengthening of time of beam influence the greatest decrease biol, effect in comparison with effect at acute exposition happens in actively renewed fabrics at relatives on duration terms of influence and turnover cycles of cellular elements of this fabric. Unequal influence of decrease

in M. of and. on tumor and normal cells in connection with distinctions in the speed of their repopulyation it is used in radiation therapy for increase radiotherapeutic interval (see).

M.'s influence by and. on biol, the effect is shown unequally depending on various linear power transmission (see. Linear power transmission ); biol, efficiency of ionizing radiation with high linear power transmission (alpha particles, heavy ions, neutrons) depends on M. of a little and.

See also Doses of ionizing radiation .

Bibliography: Akoyev I. G. Problems of post-beam recovery, page 82, 183, M., 1970; Questions of the general radiobiology (experimental and clinical data), under the editorship of M. P. Domshlak, page 147, M., 1971; Darenskaya N. G. of ides of river. Relative biological efficiency of radiations, page 173, M., 1968; Standards of radiation safety (NRB-76), page 6, M., 1978.

L. B. Koznova.