Comparison between kinetic modelling and graphical analysis for the quantification of [(18)F]fluoromethylcholine uptake in mice

BACKGROUND: Until now, no kinetic model was described for the oncologic tracer [(18)F]fluoromethylcholine ([(18)F]FCho), so it was aimed to validate a proper model, which is easy to implement and allows tracer quantification in tissues. METHODS: Based on the metabolic profile, two types of compartmental models were evaluated. One is a 3C2i model, which contains three tissue compartments and two input functions and corrects for possible [(18)F]fluorobetaine ([(18)F]FBet) uptake by the tissues. On the other hand, a two-tissue-compartment model (2C1i) was evaluated. Moreover, a comparison, based on intra-observer variability, was made between kinetic modelling and graphical analysis. RESULTS: Determination of the [(18)F]FCho-to-[(18)F]FBet uptake ratios in tissues and evaluation of the fitting of both kinetic models indicated that corrections for [(18)F]FBet uptake are not mandatory. In addition, [(18)F]FCho uptake is well described by the 2C1i model and by graphical analysis by means of the Patlak plot. CONCLUSIONS: The Patlak plot is a reliable, precise, and robust method to quantify [(18)F]FCho uptake independent of scan time or plasma clearance. In addition, it is easily implemented, even under non-equilibrium conditions and without creating additional errors.