SCINTILLATION

From Big Medical Encyclopedia

SCINTILLATION (Latin. scintillatio sparkling, blinking) — short-term flash of light (flash of a luminescence) arising in nek-ry substances (scintillators) under the influence of ionizing radiation. The method of calculation of number C. is widely applied to registration radioactivity (see), in particular during the studying of mechanisms of a salt metabolism, metabolism of proteins, fats, carbohydrates and nucleic acids, distributions and utilization in an organism of medicinal and biologically active agents etc., and also for the analysis of power ranges of ionizing radiation (see. Rentgenospektralny analysis , Spectral analysis ).

The page was observed for the first time in 1903 by English scientific W. Crookes at radiation of the screen from zinc sulfide and - particles (see. Alpha radiation ). The method of registration of alpha particles by means of calculation of number C. formed the basis of work of a stsintariskop — one of the first devices for radioactivity measurement. Highly sensitive scintillation counters are developed, the major components to-rykh are scintillator, the receiver and the converter of optical radiation in electric impulses — the photoelectronic multiplier (see. Photo multipliers ). Page — a special case of a luminescence (radio luminescence). Origins same S., as luminescences: separate atoms or molecules of scintillator due to energy of charged particles of ionizing radiation (see. Ionizing radiation ) turn into excited state; the subsequent transition to a ground state can be followed by emission of light quantums (see. Luminescence , Molecule ).

As scintillators use various inorganic and organic matters (firm, liquid, gaseous); inorganic scintillators are more often in the form of transparent crystals (NaJ, ZnS, etc.), organic — in the form of crystals (naphthalene, stilbene, anthracene etc.) and the special plastic or liquids representing mix of solvent (e.g., toluene, dioxane) and the substances dissolved in it — flyuor, e.g., 2,5-di-feniloksazol (RRO), 1,4-bis-2-(4 methyl) - 5feniloksazol (POPOP).

Add activating impurities to inorganic scintillators (e.g., at monocrystals of sodium iodide there are atoms of thallium, to-rye promote highlighting by a monocrystal of quanta of visible light. In organic scintillation mixes flyuorofor absorb the light quantums radiated at a luminescence by molecules of solvent and highlight in more long-wave spectral range, the corresponding maximum sensitivity of the photocathode of the photoelectronic multiplier.

The page, arising in solid scintillators, is used for registration of gamma radiation since beta radiation is absorbed by an aluminum container of a crystal, and gamma quanta pass through it; the crystal has the big density, small time of highlighting that causes big counting effeciency and high resolving power of the scintillation counter.

The villages arising in liquid scintillation mixtures use for registration of beta radiation. At the same time the test piece or is suspended in solution of scintillator, or dissolved in it. The internal arrangement of a sample gives the chance with big efficiency to register soft beta radiation.

The highly effective method of definition of activity of gamma-emitters gives the chance to widely use such radioisotopes in medicobiological researches as 22Na, 24Na, 42K, 59Fe, 55Fe, 131 I, etc. (see. Isotopes ). With their help determine the speed of a blood-groove, study permeability (see) cellular membranes, distribution of radioisotopes in this or that body (e.g., in a brain, a thyroid gland, sialadens) is normal or at pathology etc.

In biological researches such soft beta emitters as 14C, and 3H are widely used. With their help determine the total amount of water in an organism, study mechanisms of absorption of proteins, fats and carbohydrates, marked 14 C, carry out testing of pharmaceuticals, marked 3H and 14C, numerous researches in the field of immunology, virology and medical microbiology with use of biologically important connections, marked 3H and 14C.

See also Radio isotope diagnosis .



Bibliography: To label D. Scintillation counters, the lane with English, M., 1955; Vang Ch. and Willis D. Radio-indi-katorny a method in biology, the lane with English, M., 1969; About with t of e r m and L. A N. Researches of biological macromolecules electrofocusing, immunoelectrophoresis and tracer techniques, page 155, M., 1983


L. G. Yaglova.

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