Currently there existed no specific diagnostic test of Parkinson's Disease. Accurate diagnosis is of great interest because of the reduction in health cost and disease co-morbidity, improvement in effective treatment course and avoidance of un-necessary intervention. Our preliminary result showed superior performance from diffusion kurtosis imaging, a new development in MRI since 2007, on the diagnosis of Parkinson's Disease when compared to conventional diffusion MRI. The study proposes to validate the diagnostic value of diffusion kurtosis in major basal ganglia regions using a cross-sectional study and to assess the prognostic value through 3-year longitudinal follow-up. Furthermore, the iron content as well as global white matter involvement in both PD and PD plus syndrome patients will be assessed. The difference in MRI information between PD and PD plus syndrome patients will then be addressed in a comprehensive manner.