One-day protocol for imaging of the nigrostriatal dopaminergic pathway in Parkinson's disease by [I-123]FPCIT SPECT

Parkinson's disease is characterized by degeneration of dopaminergic neuron s, resulting in loss of dopamine transporters in the striatum. Recently, th e tracer I-123-N-omega-fluoropropyl-2 beta-carbomethoxy-3 beta-(4-iodopheny l)nortropane (FPCIT) was developed for imaging dopamine transporters with S PECT. The purpose of this study was to develop an [I-123]FPCIT SPECT protoc ol for routine clinical studies. Methods: We examined the time course of [I -123]FPCIT binding to dopamine transporters in 10 healthy volunteers and 19 patients with Parkinson's disease. Results: We found that the time of peak specific striatal [I-123]FPCIT binding was highly varied among subjects, b ut specific binding peaked in all controls and patients within 3 h postinje ction. Between 3 and 6 h, the ratio of specific-to-nonspecific striatal [I- 123]FPCIT binding was stable in both groups, although, as expected, it was significantly lower in patients. In the patients, [I-123]FPCIT binding in t he putamen was lower than in the caudate nucleus, and contralateral striata l binding was significantly lower than ipsilateral striatal binding. The su bgroup of patients with hemi-Parkinson's disease showed loss of striatal do pamine transporters, even on the ipsilateral side. Conclusion: For routine clinical [I-123]FPCIT SPECT studies, we recommend imaging at a single time point, between 3 and 6 h postinjection, and using a tissue ratio as the out come measure. The [I-123]FPCIT SPECT technique is sensitive enough to disti nguish control subjects from patients with Parkinson's disease, even at an early stage of the disease.