Examples of various fits. (A) The standard single-tissue compartment models fitted to the entire 60 min (1T2k60, red line) and only to the first 10 min (1T2k10, green line) of data collection. The dashed green line represents an extrapolation of the 1T2k10 fit, i.e. data from 10 to 60 min were not used for fitting. (B) Fits obtained with the standard single-tissue compartment model (1T2k60, red line) and the two-tissue compartment model with fixed K
2 (2T4kVTnsfix, blue line). Fits of the unconstrained (standard) two-tissue compartment model (2T4k) were identical to those of the 2T4kVTnsfix model.