Role of 6-Fluoro-18F-l-3,4-DOPA MR-PET in Clinical Workup in Movement Disorders Cases: An Exploratory Study in a Tertiary Care Neuropsychiatric Setup.

Introduction: 6-Fluoro-18F-l-3,4-dihydroxyphenylalanine (18F-DOPA) is primarily used to differentiate nondopamine deficient symptomatic subjects from Parkinsonian disorders and various etiologies from one another, which otherwise can be challenging. The current study aimed to determine (18F)-DOPA positron emission tomography (PET) patterns in Idiopathic Parkinson's disease (IPD), nondopamine deficient symptomatic (NDDS) and other movement disorders. Materials and Methods: Sixty patients referred from neuropsychiatric outpatient department were retrospectively analyzed who underwent (18F)-DOPA magnetic resonance (MR)-PET scans. Out of 60 subjects, 36 were diagnosed with IPD, 5 were cases of other movement disorders, and 19 were normal on PET imaging (NDDS). To evaluate and quantify the tracer uptake from the PET scans, a region of interest (ROI) was drawn on the least radiotracer uptake region, and subsequently, on bilateral occipital cortex, caudate (head, body, tail), putamen (anterior, posterior), periaqueductal gray matter and red nucleus using structural MR images (MRI) for better delineation of anatomical regions. Tracer uptake ratios from each selected region were generated as SUV Results: The posterior putamen showed a significant difference between IPD and other patients with an SUV cutoff of 1.69 and 100% specificity and 99.2% accuracy for normal controls. Whereas, we observed an SUV cutoff of 1.75 and an accuracy and specificity of 100% in patients with other movement disorders. The absolute values from the caudate nucleus were demonstrating a statistical significance between other movement disorders compared to normal controls with a cutoff of 1.69 and an accuracy of 81.2%. The ratio of posterior putamen/occipital ratio was significant between IPD and normal controls, with a cutoff of 3.89 and an accuracy of 95.6%. Right caudate to occipital ratio (RCOR) was significant for differentiating between other movement disorders and normal controls with a cutoff of 3.01 and an accuracy of 95.6%. One novel finding was that occipital lobe uptake was significantly reduced in patients with IPD compared to other movement disorders. Conclusion: The findings from the current study demonstrated that hybrid imaging using 18F-DOPA PET/MRI could efficiently differentiate between various causes of Parkinson's disease with diagnostic accuracy and necessary cut-offs.