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

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