SLC6A3 and Parkinson disease: 123I-ioflupane striatal dopamine transporter SPECT (DaTSCAN) has been validated as a tool for the differential diagnosis of PD and non-degenerative tremors, and 123I-metaiodobenzylguanidine SPECT and 18F-fluorodeoxyglucose PET have been used for the differential diagnosis of PD and atypical Parkinsonism.