This investigator initiated trial is designed to measure the accuracy of diagnosis of Parkinson disease through the use of DaTscan. Currently, DaTscan is FDA approved to measure dopamine transporter densities in human tissue. This measurement can assist in distinguishing between Essential Tremor and Parkinsonian Syndromes (idiopathic Parkinson disease, Progressive Supranuclear Palsy, Multi Systems Atrophy, etc). This study will compare both clinical diagnosis of symptoms and the results of the scan to the pathological diagnosis received at time of death. Patients will be registered in the Parkinson Research Institute's brain donation program, receive a clinical diagnosis of Parkinson disease, have their brain scanned using DaTscan, and donate their tissue for research and autopsy purposes. The hypothesis of the study is that DaTscan will diagnosis Idiopathic Parkinson Disease as accurately as a clinician.