Comprehensive evaluation of early-phase FP-CIT PET as a substitute for brain FDG PET in parkinsonism

Early-phase F-18 FP-CIT PET/CT (PET_FP-CIT) has been reported to possibly replace FDG PET/CT (PET_FDG) in the differential diagnosis of parkinsonism. We investigated the correlation between PET_FP-CIT and PET_FDG to explore their potential interchangeability.

Our retrospective study included 187 participants, categorized into Parkinson's disease (PD), atypical parkinsonian disorders (APD), and participants with intact dopamine transporters (DAT_intact). We analyzed the correlation of standardized uptake value ratios (SUVR) from early-phase PET_FP-CIT and PET_FDG scans across 23 different brain volumes-of-interest using Pearson's correlation analysis. We conducted this analysis for all participants collectively and then separately for each group.

For all participants without grouping, a moderate correlation (with correlation coefficients R ranging from 0.360 in right putamen to 0.530 in left caudate nucleus) was observed between Early-phase PET_FP-CIT and PET_FDG. PD group showed a weak to moderate correlation (0.226 in left frontal cortex ≤ R ≤ 0.555 in right cerebellum). APD group revealed a moderate correlation with R ranging from 0.488 in right cerebellum to 0.692 in right occipital cortex. Conversely, a lack of correlation in specific areas for DAT_intact group indicated distinctions between the modalities.

Our study showed interchangeability with a moderate correlation between early-phase PET_FP-CIT and PET_FDG. However, careful consideration is needed for DAT_intact group.