COMPARISON OF I-123 LABELED 2-BETA-CARBOMETHOXY-3-BETA-(4-IODOPHENYL)TROPANE AND 3-BETA-(4-IODOPHENYL)-N-(3-FLUOROPROPYL)NORTROPANE FOR IMAGING OF THE DOPAMINE TRANSPORTER IN THE LIVING HUMAN BRAIN

Several cocaine congeners are of potential for imaging the dopamine tr ansporter (DAT). Previous studies have shown that iodine-123 labelled 2 beta-carbomethoxy-3 beta-(4-iodophenyl)tropane ([I-123]beta-CIT) is a promising radiotracer for imaging the serotonin (5-HT) and dopamine (DA) transporters in the living human brain with single-photon emissio n tomography (SPET). [I-123]beta-CIT was found to be not very practica l for 1-day DAT imaging protocols since peak DAT uptake occurs later t han 8 h. Here we report a pilot comparison of [I-123]beta-CIT and 2 be ta-carbomethoxy-3 beta-(4-iodophenyl)-N-(3-fluoropropyl)nortropane ([I -123]beta-CIT-FP), using SPET imaging in four healthy male subjects. P eak uptake of [I-123]beta-CIT-FP into the basal ganglia occurred earli er (3-4 h after injection of tracer) than that of [I-123]beta-CIT (>8 h). However, the specific DAT binding of [I-123]beta-CIT-FP in the bas al ganglia was somewhat less (0.813+/-0.047) than that of [I-123]beta- CIT (0.922+/-0.004). Imaging quality is excellent with both tracers an d they are potentially of value for brain imaging in various neuropsyc hiatric disorders.