COMPARISON OF I-123 LABELED 2-BETA-CARBOMETHOXY-3-BETA-(4-IODOPHENYL)TROPANE AND 2-BETA-CARBOMETHOXY-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 transporter (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 emission tomography (SPET). [I-123]beta-CIT was found to be not very practical for 1-day DAT imaging protocols since peak DAT uptake occurs later than 8 h. Here we report a pilot comparison of [I-123]beta-CIT and 2 beta-carbomethoxy-3 beta-(4-iodophenyl)-N-(3-fluoropropyl)nortropane ([I-123]beta-CIT-FP), using SPET imaging in four healthy male subjects. Peak uptake of [I-123]beta-CIT-FP into the basal ganglia occurred earlier (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 basal 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 and they are potentially of value for brain imaging in various neuropsychiatric disorders.