Fig. 3.
Schematic illustrations of common pharmacokinetic models and target parameters. The exchange between the extravascular extracellular space (EES, volume fraction ve) and capillary blood plasma (volume fraction vp) is determined by the plasma flow Fp and the permeability-surface area product PS. (A) Generic tissue model. (B) Conventional Tofts model (with negligible blood volume and volume transfer constant KTrans). (C) Modified Tofts model with non-negligible blood compartment. (D) Patlak model with non-negligible plasma compartment and one-way transport of contrast agent across the BBB. For the latter two models, it may be assumed that KTrans = PS for any solution fitting the data well with a non-negligible vp.