Subjects in Project 1 (20 PD and 20 HC subjects) will be asked to undergo a single bolus injection of [18F]MPPF followed by serial Positron Emission Tomography (PET) imaging scans and blood sampling for measurement of [18F]MPPF in plasma (both protein bound and free) over a period of up to 2 hours. The imaging analyses will be performed by an image-processing specialist who will remain masked to the procedures employed with each imaging acquisition. The primary imaging outcome measure will be the brain regional distribution volumes expressed as a brain tissue to plasma ratio of the radioligand, [18F]MPPF. Time to the peak uptake and amplitude of the peak uptake will be evaluated for all brain regions and the results for the PD subjects will be compared with the HC subjects.