INDIUM radioactive (Indium, In) — chemical element III of group of a periodic system of elements of D. I. Mendeleyev. Sequence number 49, at. weight 114,82. Belongs to number a little widespread in the nature, scattered elements. And. — silver-white brilliant metal, chemical analog gallium (see). And. shows variable valency, forming one - two - and connections trivalent (preferential).
And. has two stable isotopes — with mass numbers 113 (4,23%) and 115 (95,77%), however both of these isotopes can be called stable only conditionally because actually they undergo a beta decay, though with very big half-life (an order of 1014). And. possesses the greatest number of radioisotopes among all known chemical elements, namely — 25 (including 6 isomers) with mass numbers from 106 to 124.
Majority of radioisotopes And. (17) — ultrashort-lived, with second and minute half-lives; six isotopes ( 109 In, 110 In, 113M In, 115m In, 116M In, 117m In) have hour half-lives and two ( 111 In and 114m In) — longer. From all these isotopes in medicine three are used: 111 In (half-life 2,81 days), 113 m In (half-life of 99,8 min.) and 115m In (half-life 4,5 hours).
111 In receive, irradiating with alpha particles silver on reaction 109 Ag (alpha, 2n), then 111 In extract from the dissolved target with high radio isotope purity. It can be received, irradiating targets from cadmium with protons or deuterons on nuclear reactions 111 Cd (p, n), 112 Cd (p, 2n) or 110 Cd (d, n), 111 Cd (d, 2n). However at the same time other radioisotopes also are formed of natural cadmium And. Half-life 111 In (2,81 days) is close to half-lives of the isotopes which are widely applied in medicine 198 Au and 90 Y, and also maternal isotopes of the known generating systems 132 Te —> 132 I, 87 Y —> 87 MSr, 99 Mo —> 99m Tc (see. Generators of radioisotopes ). 111 In breaks up electron capture (100%) with emission of two gamma quanta with energy 0,173 (89%) and 0,247 MEV (94%); at the same time also conversion electrons and characteristic x-ray emission of cadmium are let out. gamma Radiation 111 In is in a power interval, convenient for detecting and scanning, and falls to the share of gamma radiation apprx. 90% of energy of all types of radiation 111 In. Therefore it has advantages in diagnostic use in comparison with nek-ry other isotopes, e.g. 198 Au, as well in connection with smaller beam load of the patient.
113m In breaks up isomeric transition (see. Isomerism, atomic kernels ), passing in 113 In with emission of gamma quanta with energy of 0,392 MEV (64,4%) and electrons of conversion; at the same time also x-ray characteristic emission is emitted And. breaks up as by isomeric transition (95%) with emission of gamma quanta with energy of 0,335 MEV and conversion electrons, and by a beta decay (5%) with E beta = 0,83 MEV. Measure activity and radioactive concentration of drugs with And. on their gamma radiation; at relative measurements use model radioactive solutions and spectrometer gamma sources (see. Radiators exemplary ).
113M In, 115M In usually make on the basis of generating systems. 113MIn receive as follows: irradiating enriched on isotope 112 Sn tin slow neutrons, receive a radioisotope 113 Sn which, breaking up with half-life of 115 days, passes in 113M In. Then And. chemically separate from tin in a special column; on the basis of the eluate which is washed away from the generator prepare on site, in a wedge, conditions, various radiofarm. drugs with 113 MIn. Advantage of such generating systems is that half-life of maternal substance — 113 Sn (115 days) allows to transport the generator on any distance and to reuse it for a long time (about one year). Domestic generators 113M In are issued with nominal activity in 25, 50, 100, 200 and 300 mkyur, and radioactive concentration of the washed-away eluate with 113M In at the same time shall be not less than 1,7; 3,4; 6,8; 13,6 and 20,4 mkyuri/ml respectively.
115M In receive, irradiating natural cadmium with thermal neutrons therefore it is formed 115 Cd which, breaking up with half-life 2,3 days, turns in 115M In. The last is allocated by means of the extraction generator with high radio isotope purity and further prepared necessary radiofarm. drugs. Though 115M In has close with 113M In nuclear and physical. characteristics, but generator 115M In is less perspective in connection with short half-life of maternal cadmium-115 that limits possibilities of its practical use.
And. radioactive is applied in medicine of hl. obr. on purpose radio isotope diagnosis (see). Radiofarm. injection drugs with And. are issued in the form of colloids, a citrate complex with dietilentriaminpentauksusny to - that (DTPA), etc.
Colloids radioactive And. are applied to scanning of a liver, definition of existence and anatomic parameters (a form, size, situation) of focal or parenchymatous defeats (enter intravenously 0,1 — 0,3 mkyur 111 In or 3 — 5 mkyur 113 m In); for a stsintigrafiya limf, nodes at a lymphogranulomatosis and malignant new growths (enter 0,1 — 0,2 mkyur into fabric 111 In); for definition of a blood-groove of a liver at hepatitises, cirrhosis and other her diseases (enter intravenously 20 — 50 mkkyur 111 In or 100 — 200 mkkyur 113M In). Citrate 113M In apply to scanning of cardial cavities, isotope angiocardiography and an angiography of kidneys (enter intravenously 5 — 10 mkyur); for determination of the circulating volume of blood and studying of its distribution on certain areas of a body (enter intravenously 0,1 — 0,3 mkyur). Complex 113M In with DTPA apply to definition of a glomerular filtration rate (enter 0,2 — 0,3 mkyur), researches of kidneys (a stsintigrafiya by means of the gamma camera), and also for a research of cardiovascular system by method of radio isotope angiocardiography (enter 3 — 5 mkyur).
Isotopes I. have small radio toxicity. In a workplace without the permission a dignity. - epid, services can once be used drugs I. activity to 100 mkkyura.
See also Isotopes .
Bibliography: Bochkaryov V. V. and dr New radio pharmaceutical drug and perspectives of their clinical use, Medical radio-gramophones., No. 1, page 4, 1972; L of e in and e B. I. Receiving radioisotopes, page 183, M., 1972; Radioisotope production and quality control, Tech. rep. ser. JsTs 128, Vienna, IAEA, 1971.
V. V. Bochkaryov.