Reproducibility of the kinetic analysis of 3′-deoxy-3′-[18F]fluorothymidine positron emission tomography in mouse tumor models

ObjectivesWe assessed the reproducibility of the kinetic analysis of 3′-deoxy-3′-[18F]fluorothymidine (FLT) positron emission tomography (PET) in A431 human epidermoid carcinoma and murine Lewis lung carcinoma (LLC) tumor models.MethodsWe injected 7.4 MBq of FLT (n=10 for each group) and acquired 2-h dynamic PET images. A second scan was performed 1 day later. We calculated standardized uptake value (SUV), kinetic rate constants, volume of distribution of phosphorylated FLT (Vdm), net influx constant (KFLT-CA) and influx constant by Patlak graphical analysis (KFLT-PA). The percent difference between measurements of a parameter was calculated to compare the reproducibilities of different parameters.ResultsFLT phosphorylation was higher in mice with A431 tumors than in mice with LLC tumors (P<.005). Differences in the standard deviations of the percent differences of parameters were statistically significant (P<.001) in each model. In mice with A431 tumors, SUV, Vdm, KFLT-CA and KFLT-PA had standard deviations of the percent difference of ≤20%. The most reproducible parameter was KFLT-PA, although the standard deviation (15.6%) was not statistically different from those of Vdm (15.8%), KFLT-CA (17.5%) and SUV (18.9%). In mice with LLC tumors, K1, K1/k2 and k3 had standard deviations of the percent difference of ≤20%. No macroparameters reflecting a total FLT flux had standard deviations of ≤20%.ConclusionOur results show the reproducibility of the kinetic macroparameters of FLT PET in mouse tumors with high FLT phosphorylation.