In the first year, patients with Parkinson's disease will be recruited from the outpatient clinics of movement disorders in ChangGung memorial hospital Linkou, Taiwan. The diffusion parameters in basal ganglia will be compared with a group of healthy controls. In the second year, patients with progressive supranuclear palsy and patients with multiple system atrophy will be recruited for assessment of differential diagnosis. The patients with Parkinson's Disease will return for assessment of disease severity and in the third year, for the outcome evaluation.