PET imaging and data analysis
A standard protocol was used forĀ all [18F]FDOPA PET/CT scans. All patients were instructed to adhere to a low protein diet for 24 hours, fast at least 4 hours before tracer injection, and withhold anti-parkinsonian medications (L-dopa and dopamine agonists) that could interfere with [18F]FDOPA uptake. Patients were premedicated orally with 150 mg of carbidopa 1 hour prior to injection with 250 MBq [18F]FDOPA, and imaging started 110 minutes post-injection. [18F]FDOPA scanning was performed using a Biograph 64 PET/CT scanner (Siemens Medical Solutions, Malvern, PA, USA, Inc.) operating with the Somaris/5 SyngoCT 2006 software, having a 3-dimensional acquisition mode. PET images were fused to magnetic resonance T1-weighted images (MRI scanner model: 3T Siemens Trio scanner; Siemens, Munich Germany), that were performed before PET/CT scans. Semi-quantitative striatal dopaminergic function analysis was performed using the VE30 software (Siemens Medical Solutions, Malvern, PA, USA, Inc.). Interpretation was based on analysis of [18F]FDOPA uptake ratios for the putamen and caudate nucleus versus the occipital cortex as a reference.