METALLIC RADIONUCLIDES - APPLICATIONS IN DIAGNOSTIC AND THERAPEUTIC NUCLEAR-MEDICINE

Nuclear Medicine is a medical modality that utilizes radioactivity (ra diopharmaceutical) to diagnose and treat disease. Radiopharmaceuticals contain a component which directs the radionuclide to the desire phys iological target. For diagnostic applications, these nuclides must emi t a gamma ray that can penetrate the body and can be detected external ly while for therapeutic purposes nuclides are preferred that emit bet a particles and deliver highly localized tissue damage. Ga-67 citrate is employed to detect chronic occult abscesses, Hodgkin's and non-Hodg kin's lymphomas, lung cancer, hepatoma and melanoma and localizes in t hese tissues utilizing iron-binding proteins. (201)Thallous chloride, a potassium analogue, used to diagnosis coronary artery disease, is in corporated in muscle tissue via the Na+-K+-ATPase. In-111 labeled auto logous white blood cells, used for the diagnosis of acute infections a nd inflammations,takes advantage of the white cell's role in fighting infections. (111)Ln is incorporated in other radiopharmaceuticals e.g. polyclonal Igc, OncoScint CR/OV, OctreoScan and Myoscint by coupling diethylenetriaminepentaacetic acid, a chelate, covalently to these mol ecules. OncoScint CR/OV and Myoscint localize by antigen antibody inte ractions while OctreoScan is taken up by malignant cells in a receptor based process. Polyclonal IgG may share some localization characteris tics with Ga-67. Sr-89, a pure beta emitter, is used for palliation of bone pain due to metastatic bone lesions. Bone salts [Ca(PO)(4)] are increased in these lesions and this radionuclide is taken up similarly to Ca2+. Re-186 and Sm-153 bound to polydentate phosphonate chelates are used similarly and follow the phosphate pathway in lesion incorpor ation.