Iodine-123 labelledN-(2-fluoroethyl)-2β-carbomethoxy-3β-(4-iodophenyl)nortropane for dopamine transporter imaging in the living human brain

Abstract

There are several cocaine analogs which have potential for imaging the dopamine transporters (DAT). Earlier studies have shown that iodine-123 labelled 2β-carbomethoxy-3β-(4-iodophenyl)tropane ([¹²³I]β-CIT) andN-(3-fluoropropyl)-2β-carbomethoxy-3β-(4-iodo-phenyl)nortropane ([¹²³I]β-CIT-FP) are promising DAT imaging agents in the living human brain with single-photon emission tomography (SPET). Here we report a pilot comparison of [¹²³I]β-CIT and [¹²³I]β-CIT-FP with a new tropane derivative, [¹²³I]N-(2-fluoroethyl)-2β-carbomethoxy-3β-(4-iodophenyl)nortropane ([¹²³I]β-CITFE), using SPET imaging in four healthy male subjects. Peak uptake of [¹²³I]β-CIT-FE into the basal ganglia occurred very rapidly (0.5 h after injection of tracer), after which the striatal washout obeyed a bi-exponential form. The specific DAT binding of [[¹²³I]β-CIT FE into the basal ganglia was somewhat less (0.785 ± 0.117) than that of [¹²³I]β-CIT (0.922 ± 0.004) or [¹²³I]β-CIT-FP (0.813 ± 0.047). All these tracers have excellent imaging quality in healthy control subjects. However, the relatively fast washout of [¹²³I]β-CIT-FE and low temporal resolution of older SPET cameras may limit the use of this tracer to the measurement of the DAT density.