A comparative investigation of 18F kinetics in receptors: a compartment model analysis

Full text: Some authors reported that 18F kinetics might be useful for evaluation of neuro receptors. We hypothesized that 18F kinetics may show some information about neuronal damage, and each rate constant might have statistically significant correlation with WO function. The purpose of this study was to investigate 99mTc MIBI kinetics through a compartment model analysis. Each rate constant from compartment analysis was compared with WO, T1/2, and (H/M) ratio in early and delayed phase. Different animal model were studied. After an injection the dynamic planar imaging was performed on a dual-headed digital gamma camera system for 30 minutes. An ROI was drawn manually to assess the global kinetics of 18F. By using the time-activity curve (TAC) of ROI as a response tissue function and the TAC of Aorta as an input function, we analysed 18F pharmacokinetics through a 2-compartment model. We defined k1 as influx rate constant, k2 as out flux rate constant and k3 as specific uptake rate constant. And we calculated k1/k2 as distribution volume (Vd), k1k3/k2 as specific uptake (SU), and k1k3/(k2+k3) as clearance. For non-competitive affinity studies of PET two modelling parameters distribution volume (DV) and Bmax / Kd are also calculated. Results: Statistically significant correlations were seen between k2 and T1/2 (P<0.06), k1, Vd, SU, clearance had significant correlation with not only early H/M but also delayed H/M (P<0.002 in each others). The pharmacokinetics of 18F at the injection had relation to the uptake of it at 30 minutes and 2 hours after the injection. Furthermore, some indexes had statistically significant correlation with DV and Bmax. These compartment model approaches may be useful to estimate the other related studies