SLC6A3 and Parkinson disease: To aid in the diagnosis in clinically uncertain parkinsonian syndromes (CUPS), [18F]-DOPA positron emission tomography (FDOPA-PET) and dopamine transporter (DAT) imaging using [123I]-FP-CIT single-photon emission computed tomography (further referred to as DAT-SPECT) scans can be used to visualize nigrostriatal dopaminergic neurodegeneration, a neuropathological hallmark of PD.