Quantitative analysis of donepezil binding to acetylcholinesterase using positron emission tomography and [5-11C-methoxy]donepezil

The aim of this study was to establish kinetic analysis of [5-(11)C-methoxy]donepezil ([(11)C]donepezil), which was developed for the in-vivo visualization of donepezil binding to acetylcholinesterase (AChE) using positron emission tomography (PET). Donepezil is an AChE inhibitor that is widely prescribed to ameliorate the cognitive impairment of patients with dementia. Six healthy subjects took part in a dynamic study involving a 60-min PET scan after intravenous injection of [(11)C]donepezil. The total distribution volume (tDV) of [(11)C]donepezil was quantified by compartmental kinetic analysis and Logan graphical analysis. A one-tissue compartment model (1TCM) and a two-tissue compartment model (2TCM) were applied in the kinetic analysis. Goodness of fit was assessed with chi(2) criterion and Akaike's Information Criterion (AIC). Compared with a 1TCM, goodness of fit was significantly improved by a 2TCM. The tDVs provided by Logan graphical analysis were slightly lower than those provided by a 2TCM. The rank order of the mean tDVs in 10 regions was in line with the AChE activity reported in a previous post-mortem study. Logan graphical analysis generated voxel-wise images of tDV, revealing the overall distribution pattern of AChE in individual brains. Significant correlation was observed between tDVs calculated with and without metabolite correction for plasma time-activity curves, indicating that metabolite correction could be omitted. In conclusion, this method enables quantitative analysis of AChE and direct investigation of the pharmacokinetics of donepezil in the human brain.