Quantitative Analysis for Estimating Binding Potential of the Peripheral Benzodiazepine Receptor with [11C]DAA1106

Abstract

[11C]DAA1106 is a potent and selective ligand for the peripheral benzodiazepine receptor (PBR) with high affinity. It has been reported that the density of PBR is related to brain damage, so a reliable tracer method for the evaluation of PBR would be of use. We evaluated a quantification method of [11C]DAA1106 binding in simulated data and human brain data. In the simulation study, the reliability of parameters estimated from the nonlinear least-squares (NLS) method, graphical analysis (GA), and multilinear analysis (MA) was evaluated. In GA, variation of the estimated distribution volume (DV) was small. However, DV was underestimated as noise increased. In MA, bias was smaller, and variation of the estimated DV was larger than in GA. In NLS, although variation was larger than in GA, it was small enough in regions of interest analysis, and not only DV but also binding potential (BP), determined from the k3 /k4 without any constraint, could be estimated. The variation of BP estimated with NLS became larger as k3 or k4 became smaller. In human studies with normal volunteers, regions of interest were drawn on several brain regions, BP was calculated by NLS, and DV was also estimated by NLS, GA, and MA. As a result, DVs estimated with each method were well correlated. However, there was no correlation between BP with NLS and DV with NLS, GA, and MA, because of the variation of K1 /k2 between individuals. In conclusion, BP is estimated most reliably by NLS with the two-tissue compartment model.