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.

123 I-FP-CIT and 18 F-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 123 I-FP-CIT and 18 F-FP-CIT. Therefore, in this study, 123 I-FP-CIT SPECT/CT was compared with 18 F-FP-CIT PET/CT in the same cohort of subjects. Patients with PD and essential tremor (ET) underwent 123 I-FP-CIT SPECT/CT and 18 F-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 123 I-FP-CIT SPECT/CT and 18 F-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 123 I-FP-CIT SPECT/CT and 18 F-FP-CIT PET/CT showed a positive correlation (r = .78, p < .01). However, the mean SBRs on 18 F-FP-CIT PET/CT were higher than those on 123 I-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 18 F-FP-CIT PET/CT were not significantly higher than those on 123 I-FP-CIT SPECT/CT (1.31 ± .19 and 0.98 ± .06, respectively; p = .06). These preliminary results indicate that the uptake of both 123 I-FP-CIT and 18 F-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 18 F-FP-CIT PET/CT relative to 123 I-FP-CIT SPECT/CT.