I-123 LABELED N-(2-FLUOROETHYL)-2-BETA-CARBOMETHOXY-3-BETA-(4-IODOPHENYL)NORTROPANE FOR DOPAMINE TRANSPORTER IMAGING IN THE LIVING HUMAN BRAIN

There are several cocaine analogs which have potential for imaging the dopamine transporters (DAT). Earlier studies have shown that iodine-123 labelled 2 beta-carbomethoxy-3 beta-(4-iodophenyl)tropane ([I-123]beta-CIT) and N-(3-fluoropropyl)-2 beta-carbomethoxy-3 beta-(4-iodophenyl)nortropane ([I-123]P-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 [I-123]beta-CIT and [I-123]beta-CIT-FP with a new tropane derivative, [I-123]N-(2-fluoroethyl)-2 beta-carbomethoxy-3 beta-(4-iodophenyl)nortropane ([I-123]beta-CIT-FE), using SPET imaging in four healthy male subjects. Peak uptake of [I-123]beta-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 [I-123]beta-CIT-FE into the basal ganglia was somewhat less (0.785 +/- 0.117) than that of [I-123]beta-CIT (0.922 +/- 0.004) or [I-123]beta-CIT-FP (0.813 +/- 0.047). All these tracers have excellent imaging quality in healthy control subjects. However, the relatively fast washout of [I-123]beta-CIT-FE and low temporal resolution of older SPET cameras may limit the use of this tracer to the measurement of the DAT density.