<qa>  What is the utility of diffusion tensor imaging?This project will evaluate the utility of diffusion tensor imaging DTI as an adjunctive method to improve early diagnosis of Parkinsons disease PD. Two populations will be evaluated in this study: 1 Individuals with uncertain PD diagnosis who receive a DaTscan, and 2 individuals with well characterized PD and healthy controls, drawn from the fully enrolled Parkinsons Progression Markers Initiative PPMI PD and control cohorts. 