SLC6A3 and late-onset Parkinson disease: Finally, when abnormalities in striatal uptake are suspected but are not typical findings of degenerative parkinsonism (e.g., combined ischemic lesions and early stage of PD) or the patients with clinically typical PD appear to have normal findings, follow-up [18F]FP-CIT imaging after 1–2 years is advisable, and quantitative analysis can provide additional information because degenerative parkinsonism shows rapid progression of DAT loss compared to non-degenerative parkinsonism [37, 38].