From Big Medical Encyclopedia

MARKED CONNECTIONS — chemical compounds into which structure as «tag» the radioactive nuclide is entered. For «tag» of one such connection several radionuclides or a heavy stable isotope of one of the elements which are its chemical part can be used.

M of page apply in biology and medicine to studying of a metabolism, hormonal balance, features of distribution, napr, in a cell, various biologically active agents, funkts, states fiziol, systems, structural features of various bodies and fabrics, etc.

Distinguish inert M. of page, to-rye it is long circulate in blood and M. of page physiologically tropny to a nek-eye to bodies and systems do not enter exchange processes, and. Apply M. to medical researches of page in the form of organic and inorganic radio pharmaceuticals (see).

M.C. is created on the basis of the radionuclides received by hl. obr. on nuclear reactors. In to radio isotope diagnosis (see) M. of page on the basis of generating radionuclides were widely adopted — 99m Tc (from 99 Mo) and 113m In (from 113 Sn). Also apply the ultrashort-lived, produced on a small-size cyclotron radionuclides, to-rye can be entered into an organism in the form of gases ( 13 N, 15 O), as a part of the prepared ex tempore of drugs ( 123 I, 52 Fe), in the form of «tag» of organic compounds ( 11 With — glucose, 11 With — amino acid). Radionuclide is entered into chemical connection by organic synthesis, chemical or exchange reactions; in some cases radioactive «tag» can be implemented only in the course biol, M.'s synthesis by the village in an organism.

Speed, about a cut various M.S. pass through fiziol, system, is various, and time of establishment of a so-called equilibrium state (the maximum accumulation or the established distribution) at a small speed is measured for days, at average — hours, at big — minutes and seconds. Pages are quickly brought by Nek-rye M. out of an organism — them elimination half-life (see) it is limited for minutes or hours, others — slowly since their elimination half-life is measured for days and months.

M.'s choice by the village in biol, researches depends on the purpose of an experiment; in a wedge, diagnosis preference is, as a rule, given to M. by the village having the bigger speed of removal from an organism with the most short-lived radioactive nuclide generating gamma radiation with energy in the range of 0,1 — 0,3 MEV.

M of page usually arrive to the consumer in the form of sterile radio pharmaceuticals. Preparation of separate portions of M. of page, napr, for intravenous administration, carry out under radiometric control with observance of rules of an asepsis and antiseptics.

M of page enter into an organism in strictly regulated quantity providing reliability of results at the minimum beam loading which is not exceeding marginal exposure doses (see. Marginal doses of radiation ).

See also Isotopes .

Bibliography: Zubovsky G. A. Gammastsintigrafiya, page 15, M., 1978; P about and N-sky Page 3. and Shnol S. E. Isotopes in biochemistry, M., 1963; With and in about sh and N-sky D. S., etc. Devices for radio isotope diagnosis in medicine, page 10, M., 1978; The Nuclear medicine, the Report of the Joint committee of experts of IAEA/WHO on use of ionizing radiation and radioisotopes in the medical purposes (nuclear medicine), the lane with English, M., 1977; W about 1 1‘ And. P. Medical cyclotrons, in book: Med. radionuclide imaging, v. 1, p. 343, Vienna, 1977.

D. S. Sivoshinsky.