Quantification Of Ampa Receptors Using C-11-K-2 Considering White Matter As Reference Region

1577 Introduction: This study aims to investigate appropriate implementations to quantify AMPA receptors (AMPAR) using the novel PET tracer 11C‒K-2. AMPAR concerns cortical reorganization, and it is expected to be applied for various brain diseases such as epilepsy or psychological disorders. K-2 presents typical reversible kinetics, and BPND is found to be a quantitative index to AMPAR using epileptic patients; the BPND is correlated with the amount of AMPAR directly measured using the resected brain tissues (OP‒648 at EANM2018 and no. 325 at SNMMI2019). We show a demonstrative image; these are cases of schizophrenia, and a focal decrease of AMPAR is found. We investigate the validity of white matter as a reference region compared with the results obtained from dynamic scans with arterial blood sampling using Logan Graphical Analysis (LGA). Methods: We conducted 60-min dynamic scans to 6 healthy controls with arterial blood sampling, and computed total distribution volume (VT) using LGA where t* was 30 min. We also computed BPND with a white matter as a reference region where we did not assumes the value of k2 at a reference region with varying t* from 10 to 40 min after administration. We placed 11 ROIs on typical brain regions, and we computed VT and BPND using the averaged tTACs. The VTs were compared: one is directly computed from LGA with pTAC at a white matter, and the other is the estimated VT using a linear relationship between BPND and VT in which the VT at a reference region is at the point of BPND=0. Results: No significant difference is detected between both VT (p<0.05). The change of t* for LGA causes a small change in BPND within 2%. Conclusions: White matter is applicable to reference region for AMPAR quantification with K-2 because these results on VT and our previously reported data of an immunoblot that presented no AMPAR exists in white matter. Moreover, BPND is independent of t* in LGA, and that shows rapid irreversible kinetics for K-2.