In another study Liu et al. (94) used the PET tracer N-123C-methyl-piperidin-4-yl propionate to scan for acetylcholinesterase activity in 4 patients with LRRK2 Parkinson's disease, 16 LRRK2 mutation carriers without Parkinson's disease, eight patients with idiopathic Parkinson's disease, and 11 healthy controls. The gene discussed is LRRK2; the disease is Parkinson disease.