ABSTRACT
The aim of this study was to compare two PET ligands, 6-[(18)F]fluoro-L-dopa ([(18)F]FDOPA) and (18)F-labeled CFT, 2beta-carbomethoxy-3beta-(4-[(18)F]-fluorophenyl)tropane ([(18)F]CFT), in detecting presynaptic dopaminergic hypofunction in early Parkinson's disease (PD). These ligands reflect different aspects of presynaptic dopaminergic function, since [(18)F]FDOPA mainly reflects 6-[(18)F]fluorodopamine (fluorodopamine) synthesis and storage whereas [(18)F]CFT uptake is related to dopamine transporter function. Eight de novo patients with PD who had never been on antiparkinsonian medication were investigated with [(18)F]FDOPA and [(18)F]CFT PET. Five healthy volunteers were studied as controls. In PD patients, both [(18)F]FDOPA and [(18)F]CFT uptakes were significantly reduced both in the contralateral and ipsilateral anterior and posterior putamen. The reduction was greatest in the contralateral posterior putamen (to 28% of control mean for [(18)F]FDOPA, P < 0.0001 and to 16% for [(18)F]CFT, P < 0.0001). Individually, all patients' [(18)F]FDOPA and [(18)F]CFT uptake values in the contralateral anterior and posterior putamen were below 3 SD of the control mean. In the caudate nucleus, the mean uptake of both tracers was significantly reduced both ipsilaterally and contralaterally, but less severely than in the putamen (to 69% of the control mean for [(18)F]FDOPA, P = 0.003 and to 60% for [(18)F]CFT, P = 0.001 contralaterally). Our results show that both [(18)F]FDOPA as well as [(18)F]CFT sensitively detect presynaptic dopaminergic hypofunction in early PD. They demonstrate a considerable reduction of tracer uptake that is greatest in the posterior putamen, followed by the anterior putamen and the caudate nucleus.