NUCLEAR MEDICINE-IN VITRO, IN VIVO TESTS-LESSON 141
NUCLEAR MEDICINE TESTS: Procedures: Nuclear medicine physicians use two types of tests in the diagnosis of disease. In vitro (in the test tube) procedures and in vivo (in the body) procedures. In vitro procedures involve analysis of blood and urine specimens using radioactive chemicals. For example, a radioimmunoassay (RIA) is an in vitro procedure that combines the use of radioactive chemicals and antibodies to detect hormones and drugs in a patient's blood. The test allows the detection of minute amounts of drug. RIA is used to monitor the amount of digitalis, a drug used to treat heart disease in a patient's bloodstream and can detect hypothyroidism in newborn infants. In vivo tests trace the amounts of radioactive substances within the body. They are given directly to a patient to evaluate the function of an organ or to image it. For example, in tracer studies a specific radionuclide is incorporated into a chemical substance and administered to a patie