BCHE and Parkinson disease: Perez-Lloret and Barrantes (15) studied 17 fallers and 27 non-fallers with PD with PET scans utilizing [11C] methyl-4-piperidinyl propionate acetyl-cholinesterase (a marker for cholinergic activity) and [11C] dihydro-tetrabenazine vesicular monoamine transporter type (a marker for dopaminergic activity).