Intrastriatal analysis of FDOPA PET scans for differentiation of Parkinsonian Disorders

Aim: L-3,4-dihydroxy-6-18F-fluorophenylalanine (FDOPA) PET allows quantification of presynaptic dopaminergic functioning in vivo. It assesses the function of nigrostriatal projection neurons, particularly dopamine release in the striatum. Previously, it was postulated that Idiopathic Parkinson’s disease (IPD) preferentially affects the posterior putamen. This study aims to investigate the potential of FDOPA PET scans to differentiate atypical parkinsonian disorders (APD), idiopathic parkinson’s disease (IPD) and healthy controls. Materials & Methods: 58 patients (28 IPD, 13 APD and 17 controls) who underwent FDOPA PET scan as part of the clinical evaluation and who were diagnosed by movement disorder specialists, were retrospectively analyzed. Average age of IPD, APD and controls was 61.0, 69.6 and 65.4 respectively. All were scanned on a Siemens HR+ camera, with injected dose of 200MBq and pretreated with carbidopa, 2.5 mg/kg orally. After spatial normalization of images in standard MNI space (Montreal Neurological Institute), predefined sets of volumes of interest (VOIs) were used to sample values from striatum and the occipital reference region. Outcome values were striatal-to-occipital ratios (SOR), intrastriatal ratios and slope of multiple in-line spherical VOIs through the striatum anterior to posterior (gradient analysis). All values were compared between groups using ANOVA test and ROC curves were calculated. Results: SOR values showed no statistically significant difference between APD and IPD patients. When analyzing intrastriatal ratios, caudate-to-putamen was found to be statistically significant when comparing APD and IPD (p