Dopamine transporter (DAT) imaging is a key supporting diagnostic examination to distinguish patients with idiopathic parkinsonism (PS) (e.g., Parkinson’s disease, multisystem atrophy, progressive supranuclear palsy, and Lewy body dementia) from patients with Parkinson-like symptoms with preserved dopaminergic function. This evidence concerns the gene SLC6A3 and Lewy body dementia.