ABSTRACT
Non-imaging studies may be carried out with in vivo administration of radiochemicals or radiopharmaceuticals incorporating a wide range of radionuclides including pure beta emitters, beta-gamma emitters, and electron capture nuclides. The understanding and quantitation of temporal events in biologic systems has been greatly facilitated through the use of stable and radioactive isotopes and indicator-dilution techniques for the study of body composition and estimation of blood flow. Radioactive indicator techniques for measurements of blood flow have been described for both nondiffusible and diffusible tracers. When a radioactive gas is injected as a bolus into the arterial supply to an organ, the flow measurement is limited to the portion of the organ supplied by the injected artery. One of the most interesting applications of radioisotope methodology is for analytical determination of trace constituents in biological fluids in a highly selective and specific manner.
