Comparison of iodine-123 labelled 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

Abstract

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 ([123I] 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). [123I] 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 [123I] beta-CIT and 2 beta-carbomethoxy-3 beta-(4-iodophenyl)-N-(3-fluoropropyl)nortropane ([123I] beta-CIT-FP), using SPET imaging in four healthy male subjects. Peak uptake of [123I] beta-CIT-FP into the basal ganglia occurred earlier (3-4 h after injection of tracer) than that of [123I] beta-CIT (> 8 h). However, the specific DAT binding of [123I] beta-CIT-FP in the basal ganglia was somewhat less (0.813 +/- 0.047) than that of [123I] 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.