Figure 2.
Graphical representation of common 2-tissue compartment models. Model (A) is consisting of three components and each is a function of time expressed as time activity curves. Input function, Ca(t) consists primarily of arterial blood and interstitial space close to vessels. The C1(t) compartment represents unbound tracer in tissue whereas C2(t) compartment represents bound tracer. This model contains three kinetic parameters, k1-3. Model (B) contains the same number of compartments but kinetic parameter also includes the transport rate constant k4. Moreover, the netto influx parameter, Ki can be calculated based on k1-3 in a irreversible model, and k1-4 can be used to calculate the distribution volume, Vd in a reversible model.