(Accepted Poster at RSNA 2018, Tue Nov 27 2018 12:45PM - 1:15PM) PURPOSE Parkinson’s disease (PD) in a progressive neurodegenerative disorder that results in loss of dopaminergic neurons in the striatum. Its clinical diagnosis relies on the presence of cardinal motor symptoms of bradykinesia, rigidity, resting tremors and postural instability. 99mTc-TRODAT-1 is a sensitive diagnostic test for early detection of PD. We evaluate 99mTc-TRODAT-1 SPECT imaging patterns and assess their correlation with disease severity in clinically diagnosed patients of Parkinson’s disease. METHOD AND MATERIALS The study included 241 diagnosed patients of clinically probable PD who underwent 99mTc-TRODAT-1 SPECT scan. Binding ratios (BR) were calculated for each striatum, caudate, and putamen individually, by drawing region of interest (RoI). Occipital cortex was taken for background correction. Correlation of binding ratio with increasing clinical stage was derived. RESULTS Median binding ratio (BR) was the least in the contralateral putamen for all stages of Modified Hoehn and Yahr. A statistically significant negative correlation was found between increasing disease severity and BR in all sub-regions of striatum. Significant decline was noted in the binding ratio of the putamen as compared to caudate. Patients were further clinically categorized into postural-instability gait disorder (PIGD) group, and tremor-dominant PD (TD) group. No significant asymmetry was found between the left and right striatum in patients belonging to PIGD group and in those with bilateral tremors without lateralization. Significant correlation was found between decline in striatal binding on both the sides, even in early stages when patients presented with unilateral symptoms. CONCLUSION 99mTc-TRODAT-1 SPECT can successfully detect and assess disease severity of PD. CLINICAL RELEVANCE/APPLICATION 99mTc-TRODAT-1 SPECT should be used for early detection and assessment disease severity of PD and thereby guide treatment.