This study is designed to determine if magnetic resonance imaging (MRI) measures can be used to diagnose and monitor the progression of Parkinson's disease (PD) while distinguishing between PD and parkinsonisms [conditions that are PD look-a-like diseases such as progressive supranuclear palsy (PSP) or multiple system atrophy (MSA)] when combined with changes in certain proteins in body fluids that are related to iron (Fe).