title: Radiohalogen-labeled imaging agents. 3. Compounds for measurement of brain blood flow by emission tomography.
abstract: The radioiodine-labeled amines currently available as brain-imaging agents, based on our previous work and that of others, are prepared either by exchange labeling or by direct iodination of a protected intermediate. The intrinsic slowness of these processes limits their potential for use with the positron-emitting 122I, as it has a half-life of only 3.6 min. This isotope has advantages of a low dose to the patient and availability from a generator containing the parent 20-h 122Xe. To develop a radiopharmaceutical in which 122I could be utilized, we prepared a number of secondary and tertiary amines (maintaining the 2,5-dimethoxy substitution pattern which allows direct iodination at the 4-position) with 131I. The organ distributions of these compounds were studied, and the best properties were found in the N,N-dimethyl homologue (2,5-dimethoxy-N,N-dimethyl-4-iodoamphetamine). This compound was successfully synthesized in a matter of seconds, with a chemical yield and radioactive purity both in excess of 90% and an incorporation efficiency of radioiodine of about 40%.
mesh_terms: D000662:Amphetamines; D000818:Animals; D001921:Brain / Q000000981:diagnostic imaging*; D002560:Cerebrovascular Circulation; D004285:Dogs; D006219:Halogens; D007457:Iodine Radioisotopes / Q000008:administration & dosage; D011876:Radionuclide Generators; D012039:Regional Blood Flow; D014018:Tissue Distribution; D014055:Tomography, Emission-Computed; D014980:Xenon Radioisotopes
chemical_list: D000662:Amphetamines; D006219:Halogens; D007457:Iodine Radioisotopes; D014980:Xenon Radioisotopes; C079285:2,5-dimethoxy-N,N-dimethyl-4-iodoamphetamine