@misc{oai:repo.qst.go.jp:00071448,
 author = {Ito, Hiroshi and Ikoma, Yoko and Seki, Chie and Kimura, Yasuyuki and Kawaguchi, Hiroshi and Takuwa, Hiroyuki and Tajima, Yosuke and Yamaya, Taiga and Suhara, Tetsuya and Kanno, Iwao and 伊藤 浩 and 生駒 洋子 and 関 千江 and 木村 泰之 and 川口 拓之 and 田桑 弘之 and 田島 洋佑 and 山谷 泰賀 and 須原 哲也 and 菅野 巖},
 month = {May},
 note = {Objectives: In PET studies with radioligands for neuroreceptors, tracer kinetics is described by the two-tissue compartment model (2-TCM), and binding parameters including the total distribution volume (VT), nondisplaceable distribution volume (VND), and binding potential (BPND) can be determined from model parameters estimated. The stability of binding parameter estimates depends on the kinetic characteristics of radioligand. To describe kinetic characteristics of radioligands, we previously developed a new graphic plot analysis in which VND and VT are estimable from the x-intercept of regression line for early and delayed phase, respectively [1]. In this study, the kinetics of radioligands for neuroreceptors was evaluated using this graphic plot analysis in simulated brain tissue time-activity curves (TACs) with various binding parameters, and compared the shape of these graphic plots to accuracy of binding parameters estimated by the 2-TCM.
Methods: The arterial input function (AIF) was generated using the exponential model. TACs for 90 min were generated with the AIF and assumed kinetic parameters according to the 2-TCM. To generate TACs, influx rate constant (K1) and VT were assumed to be 0.15 mL/mL/min and 5 mL/mL, respectively. The dissociation constants (k4) were assumed to be 0.01-0.10 min-1. BPND were assumed to be 1.5-9.0. The graphic plot analysis was applied to these simulated TACs, and curvature of plot for each TAC was evaluated visually. TACs with several noise levels (1-7%) were also generated with various kinetic parameters mentioned above, and the bias and variation of binding parameters estimated by the 2-TCM was calculated in each TAC.
Results: The graphic plots showed larger curvature for TACs with higher specific binding and slower dissociation of specific binding (Fig. 1). The radioligands with rapid or slow dissociation reached the equilibrium condition earlier or delayed, respectively (Fig. 1). The quartile deviations of VND and BPND determined by the 2-TCM were smaller for radioligands with slow dissociation.
Conclusions: The larger curvature of graphic plots for radioligands with slow dissociation might indicate a stable determination of VND and BPND by the 2-TCM. For investigation of kinetics of radioligands, such kinetic characteristics should be considered., The 10th International Symposium on Functional NeuroReceptor Mapping of the Living Brain (NRM2014)},
 title = {Visual evaluation of kinetic characteristics using a new graphic plot analysis in PET neuroreceptor imaging},
 year = {2014}
}