抄録
Patlak analysis, which estimates the net FDOPA influx constant (Ki) by linear regression of data acquired from [18F] FDOPA PET study, is widely employed in the diagnosis of neurological disorder, such as Parkinson's disease. In Ki estimation by Patlak analysis, it is assumed that the metabolites of radioligand do not diffuse out of the tissue during PET scan. However, [18F] F-Dopamine, synthesized from [18F] FDOPA, is rapidly metabolized and its metabolites diffuse from the tissue. We aimed at the evaluation of the effect of dopamine metabolism and the clearance of its metabolites on Ki estimated by Patlak analysis. For this purpose, we developed a model describing the detailed pathway of dopamine kinetics in the striatum, and a standard time-activity curve (TAC) was generated based on this model and [18F] FDOPA PET data of a monkey. And TACs in case of altering the dopamine metabolism or the clearance of its metabolites were simulated. Then, we evaluated Ki values estimated by Patlak analysis for these simulated TACs. Ki was increased when the dopamine metabolism to DOPAC (k9dopac) and the clearance of DOPAC and HVA (k11dopac, k11hva) were altered. The results suggest that Ki could be biased by the influence of the metabolism of dopamine and clearance of its metabolites. Therefore, it is important to consider these biases in the interpretation of Ki value estimated Patlak analysis.
