ACHE and Parkinson disease: Previous in vivo imaging studies of brain cholinergic systems in Parkinson’s disease mostly relied on PET acetylcholinesterase substrate tracers, which are indirect markers of cholinergic terminal integrity because acetylcholinesterase may have both pre- and post-synaptic expressions and its activity may vary over the course of the disease.62 The big advantage of 18F-FEOBV PET imaging is the strict correlation with presynaptic cholinergic terminals.21,63 A final strength is the use of a validation cohort comparing GBA-PD with a second matched non-GBA-PD group to validate our results.