One hundred and twelve patients with Parkinson's Disease will be recruited in the first year and followed up for 3 years. Another 112 healthy controls will be included. This is to validate the diagnosis and assess the prognosis. Another 30 patients with Parkinson's Disease, 15 patients with progressive supranuclear palsy and 15 patients with multiple system atrophy will be recruited in the 2nd year for differential diagnosis. The imaging protocol will include both diffusion tensor and diffusion kurtosis imaging. Susceptibility weighted imaging will be included for iron content estimation. The targeted anatomy will include regional changes in basal ganglia, midbrain as well as thalamus, and global white matter changes using tract based spatial statistics. The statistical analysis will use receiver operative characteristics to assess the diagnostic performance, Spearman's ranked correlation for correlation with disease severity and net reclassification improvement for differential diagnosis. The prognostic value will be determined by the decline rate and the quality of life.