Schematic overview of the raw data model. The arterial concentrations (C_arterial) were modeled with a three compartmental model (with parameters V1–3_arterial) with intercompartmental clearances (parameters Q2 and Q3) and an elimination rate constant equal to the sum of parameters k14 and k15. Rate constants k14 and k15 were defined as the arterial elimination rate constant divided by 2. To allow for a delay between the arterial and venous plasma concentrations, two venous delay compartments were added (V_slow,venous and V_fast,venous) with elimination half-lives t_½,slow and t_½,fast. Note that k₁₄ = k₁₅ = k₁₀/2 (elimination rate).