Error analysis for quantification of [C-11]FLB 457 binding to extrastriatal D-2 dopamine receptors in the human brain

To estimate receptor binding of ligand by positron emission tomography (PET ) without an arterial input function, several quantitative approaches based on the use of a reference region have been proposed. We compared three app roaches for quantifying extrastriatal D-2 dopamine receptors using [C-11]PL B 457. The PET measurements were performed on seven healthy men. Binding po tential (BP) of [C-11]FLB 457 was calculated by the reference tissue model method, transient equilibrium method, and late time method. The reference t issue model describes the time-activity curve in a brain region in terms of that in the reference region, assuming that the levels of nondisplaceable radioligand binding in both regions are the same. The transient equilibrium theoretically occurs when the derivative for specific binding is zero. Wit h the late time method, BP is calculated by integrating a late part of the time-activity curve. BP values obtained by all methods were in good agreeme nt with those obtained by the kinetic approach, and the highest coefficient of correlation was observed in the reference tissue model method. In the s imulation study, the error of BP calculated by the reference tissue model m ethod was smallest. Moreover, the effect of the difference in the influx ra te constant K-1 between the brain and the reference regions on BP was nearl y avoided as theoretically predicted. We concluded that the reference tissu e model method is most suitable for calculating BP of extrastriatal D-2 dop amine receptors with [C-11]FLB 457. (C) 2001 Academic Press.