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.