Head-to-head comparison of 18 F-FP-CIT and 123 I-FP-CIT for dopamine transporter imaging in patients with Parkinson's disease: A preliminary study.

I-123-FP-CIT and F-18-FP-CIT are radiotracers which are widely used to diagnose Parkinson's disease (PD). However, to our knowledge, no studies to date have made head-to-head comparisons between I-123-FP-CIT and F-18-FP-CIT. Therefore, in this study, I-123-FP-CIT SPECT/CT was compared with F-18-FP-CIT PET/CT in the same cohort of subjects. Patients with PD and essential tremor (ET) underwent I-123-FP-CIT SPECT/CT and F-18-FP-CIT PET/CT. Visual and semiquantitative analyses were conducted. The specific binding ratio (SBR) and putamen to caudate ratio (PCR) were compared between subjects who underwent I-123-FP-CIT SPECT/CT and F-18-FP-CIT PET/CT. Visual analysis showed that the striatal uptake of both radiotracers was decreased in the PD group, whereas striatal uptake was intact in the ET group. The SBR between I-123-FP-CIT SPECT/CT and F-18-FP-CIT PET/CT showed a positive correlation (r=.78, p<.01). However, the mean SBRs on F-18-FP-CIT PET/CT were higher than those on I-123-FP-CIT SPECT/CT (2.19 +/-.87 and 1.22 +/-.49, respectively; p<.01). The PCRs in these two modalities were correlated with each other (r=.71, p<.01). The mean PCRs on F-18-FP-CIT PET/CT were not significantly higher than those on I-123-FP-CIT SPECT/CT (1.31 +/-.19 and 0.98 +/-.06, respectively; p=.06). These preliminary results indicate that the uptake of both I-123-FP-CIT and F-18-FP-CIT was decreased in the PD group when compared with the ET controls. Visual analyses using both methods did not affect the diagnostic accuracy in this study. However, semiquantitative analysis indicated a better contrast of F-18-FP-CIT PET/CT relative to I-123-FP-CIT SPECT/CT.