Radioactivity and life. YK Kudrytski (MD) 1971 Part 11.

The conditions of irradiation is dependent on the distribution prostransgpsnpogo radiation. Total harakgeristikop in this respect is the 'rule: the smaller the volume obluchiemoy tissue, the smaller, respectively, and biological effect.
Thus, the dose of 600 r whole-body irradiation with an absolutely lethal to humans. At the same time when radiotherapy doses are given in one session, nanaplivaya for the entire course of treatment thousands, and sometimes 10 -] 5000 X-ray, as this can expose a relatively small
Scheu part of the body. ,
X-ray procedures during the dose is sometimes particularly difficult to diagnose cases as high as tens or even hundreds of X-rays. However, due to local effects such exposure does not bring significant harm to the patient.
Many radioactive isotopes, getting into the body, according to their chemical properties are deposited in certain organs. For example, radioactive iodine-131), as well as the usual neradioaktnvnyyego isotope (I-127), mainly retained in the thyroid gland. These are his property during radioisotope diagnosis 'disease ~ itovidnoy cancer, as well as in radiation therapy of some diseases it ~ anii, since kontseptriruyas predominantly in the gland, radioactive race decay, creates the necessary dose in its tissues, relatively little irradiation of the rest' the body.
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Another example is the so-called osteotropic "radioactive isotopes, which are chemical analogues of calcium. So, like calcium, they are mainly deposited in bone tissue. These include radium, all now known strontium-90 and other radioactive isotopes. Osteotropic radioactive isotopes is irradiated with the main way bone and bone marrow. Therefore, the accumulation of large quantities of these isotopes can develop bone disease. Among the latter are especially dangerous bone sarcomas, and blood diseases: leukemia, anemia, and others.
Thus, a type of local exposure to radiation is radiation, obuslovlentsoe decay of incorporated radioactive isotopes, particularly the exchange which leads to an uneven distribution of the body. Estestvenpo that this biological effect is much smaller than the total exposure. However, at high concentrations of radioactive isotopes in any organ can be on. accumulate a large dose that can cause his defeat. Such bodies are called critical, because the possibility of pathological changes in these limits the allowable concentration of a harmless radioactive isotopes in the body.
The biological effect depends not only on the magnitude of radiation exposure, that is, from doey, its temporal and spatial distribution, but also on the condition and characteristics of the organism.
* Osteotropic - tending to the bone.