SLC6A3 and Parkinson disease: The high affinity and selectivity made PE2I a highly potent tracer to image the DAT in vivo either by SPECT when labeled with 123I and by PET when labeled with 11C. In this context, [123I]PE2I demonstrated its usefulness for the differential diagnosis between patients suffering from PD and atypical parkinsonian syndromes without degeneration of striatal dopaminergic nerve endings (21).