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

Abstract 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.