a branch of radiology that studies the use of radioactive isotopes, including their use as radioactive tags for compounds, in the diagnosis of disease.
Radioisotope diagnosis was established in 1934 with the development of artificial radioactivity, which made it possible to obtain radioactive preparations (isotopes and their compounds). Upon introduction into an organism (in vivo) or the biological fluids of an organism (in vitro), radioactive preparations facilitate the study of both healthy and diseased organs and systems. The kinetics (in time and space) of radioactive preparations is recorded by radiometric methods. Special apparatus provides radiodiagnostic information in the form of numerical quantities, graphic representations, and pictures of the spatial distribution of a preparation in organs and systems (scintiscans).
The methods of radioisotope diagnosis are based on the following factors: (1) an evaluation of the degree of dilution of a radioactive preparation in the body fluids (the determination of the volume of circulating blood, water metabolism, and potassium and sodium metabolism), (2) a determination of a change (in time) in the level of radioactivity in organs and systems or in a pathological focus (the study of central and peripheral hemodynamics, hepatography, renography, and radiopneumogra-phy, the determination of the intrathyroid stage of iodine metabolism, and the study of the dynamics of the relative level of phosphorus metabolism in a pathological focus), (3) a visualization of the distribution of a radioactive preparation that has been introduced into an organism (the scanning and gamma scintigraphy of organs and systems, including the brain, thyroid, Rings, liver, kidneys, bone marrow, bones, and lymphatic system), (4) a determination of the extent of the excretion of radioactive preparations from the body or their redistribution in the body’s biological fluids (the determination of levels of gastrointestinal bleeding, protein-bound iodine in the blood, and the absorption of neutral fats), and (5) the in vitro interaction of tagged compounds with the constituents of biological fluids without the introduction of radioactive preparations into the body—specifically, the interaction of the antigen-antibody type of tagged compound (the determination of the thyroxine binding capacity of serum and the concentration of various hormones in the blood).
Two stages can be distinguished in the history of radioisotope diagnosis. During the first stage, research methods were developed and radioactive preparations were sought that most adequately reflected the condition of the organs and systems (Na131I, 131I [Hippuran], and 75Se [methionine]) and that subjected the person being examined to a minimal radiation load (preparations tagged with, for example, 99mTc and 111In). Special radiodiagnostic apparatus was also developed, including scanners, gamma radiation chambers, and multichannel radiometers.
The second stage was marked by its specialization to suit the needs of such clinical disciplines as neurosurgery, oncology, endocrinology, cardiology, and nephrology. This led to the creation of radioisotope diagnosis laboratories in many specialized research centers, hospitals, and clinics. The methods of radioisotope diagnosis are used during modern comprehensive examinations of patients.
REFERENCESFateeva, M. N. Ocherki radioizotopnoi diagnostiki. Moscow, 1960.
Zedgenidze, G. A., and G. A. Zubovskii. Klinicheskaia radioizotopnaia diagnostika. Moscow, 1968.
Quimby, E., S. Feitelberg, and S. Silver. Radioactive Isotopes in Clinical Practice. Philadelphia, 1959.
Medical Radioisotope Scintigraphy. 1972.
International Atomic Energy Agency, vols. 1–2. Vienna, 1973.
V. Z. AGRANAT and F. M. LIASS