Fig. 1

Schematic representation of the three-compartment model applied for ¹⁸F-FDG and ¹⁸F-FLT. K₁, k₂, k₃, and k₄ are rate constants (1/min) and describe the directional exchanges between the three compartments (c_plasma represents the vascular compartment, c₁ represents the free and non-specifically bound compartment, and c₂ represents the trapped compartment). K₁ and k₂ are the inflow and outflow rate constants, respectively between the plasma and the free tracer compartment, and k₃ and k₄ are the rates of phosphorylation and dephosphorylation, respectively