DaTscans have been being used in Europe since 2000 to dx PD. The scan measures dopamine levels in four quadrants of the brain. If the dopamine is low, then you have either PD or a Parkinson's plus syndrome. It can't distinguish between PD, PSP, and MSA, but it can say that your condition is either dopamine related or ET. The question that this begs is why did it take until 2009 for the FDA to accept the new drug application? How behind is this country in neuroscience?