As expected, 18F-FE-PE2I PET studies showed the ability to detect the loss of striatal DAT binding in PD (66), and small head-to-head studies with 123I-FP-CIT SPECT showed that 18F-FE-PE2I is not inferior to 123I-FP-CIT in detecting striatal DAT loss (65,67). This evidence concerns the gene SLC6A3 and Parkinson disease.