The aim of this study was to assess the utility of presynaptic dopaminergic imaging using 99mTc-TRODAT-1 SPECT/CT and 18F-FDOPA PET/CT and compare their performance in Parkinson’s disease (PD), Parkinson-plus syndrome (PPS), and essential tremor (ET).
Patients and Methods
A total of 103 patients (PD = 48, PPS = 19, and ET = 36) were enrolled prospectively. Hoehn and Yahr (H&Y) staging and MDS-UPDRS (Movement Disorder Society–Sponsored Revision of Unified Parkinson’s Disease Rating Scale) were done for PD and PPS cases. All the patients underwent 99mTc-TRODAT-1 SPECT/CT and 18F-FDOPA PET/CT brain scan. The scans were analyzed visually and semiquantitatively. Average pixel count and SUVmean of the striatum were calculated in SPECT and PET images, respectively, to calculate the specific uptake ratio of striatum (SUR). Comparison of scan findings and SURs among different groups and correlation with clinical characteristics was done.
Symmetrical comma-shaped uptake was seen in bilateral striatum in ET cases with mean SURs significantly higher than in cases of early PD (H&Y stage I and II, n = 37), PD and PPS both on SPECT and PET images (P ≤ 0.001). The mean SURs between PD and PPS showed no significant difference (SPECT, P = 0.17; PET, P = 0.61). Substantial agreement (weighted κ = 0.659) was found between 99mTc-TRODAT-1 and 18F-FDOPA for the detection of presynaptic dopaminergic dysfunction. Specific uptake ratio of striatum correlation between SPECT and PET was statistically significant (r = 0.67; P < 0.01). A negative but nonsignificant correlation was found between the SURs and H&Y staging/MDS-UPDRS.
Both 99mTc-TRODAT-1 SPECT/CT and 18F-FDOPA PET/CT showed substantial agreement and proved to be potential imaging biomarker for the detection of dopaminergic dysfunction, thus assisting in differentiating early PD/PD and PPS from ET cases.