A DaTscan is not necessary for the diagnosis of Parkinson's disease, and by itself cannot diagnose a person with Parkinson's disease, explains the National Parkinson Foundation. A DaTscan can differentiate between Parkinson's disease and other diseases, such as essential tremors.
DaTscans determine if a person has Parkinson's by measuring changes of dopamine levels in the brain, reports the National Parkinson Foundation. Parkinson's disease is characterized by the loss of cells in the area of the brain that controls movement. A small loss in these cells is a normal part of aging, but a patient with Parkinson's starts losing cells on one side of his brain, and it continues eventually to the rest of the brain. An expert can differentiate between cell loss due aging and cell loss due to Parkinson's on a DaTscan by examining the changes in dopamine levels.