Modeling 18F-FDG kinetics during acute lung injury: experimental data and estimation errors

There is increasing interest in Positron Emission Tomography (PET) of 2-deoxy-2-[18F]flouro-D-glucose ((18)F-FDG) to evaluate pulmonary inflammation during acute lung injury (ALI). We assessed the effect of extra-vascular lung water on estimates of (18)F-FDG-kinetics parameters in experimental and simulated data using the Patlak and Sokoloff methods, and our recently proposed four-compartment model. Eleven sheep underwent unilateral lung lavage and 4 h mechanical ventilation. Five sheep received intravenous endotoxin (10 ng/kg/min). Dynamic (18)F-FDG PET was performed at the end of the 4 h period. (18)F-FDG net uptake rate (Ki), phosphorylation rate (k(3)), and volume of distribution (F(e)) were estimated in three isogravitational regions for each method. Simulations of normal and ALI (18)F-FDG-kinetics were conducted to study the dependence of estimated parameters on the transport rate constants to (k(5)) and from (k(6)) the extra-vascular extra-cellular compartment. The four-compartment model described 85.7% of the studied (18)F-FDG-kinetics better than the Sokoloff model. Relative to the four-compartment model the Sokoloff model exhibited a consistent positive bias in Ki (3.32 [1.30-5.65] 10(-4)/min, p