Validation of dynamic contrast-enhanced magnetic resonance imaging-derived vascular permeability measurements using quantitative autoradiography in the RG2 rat brain tumor model

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is widely used to evaluate tumor permeability, yet measurements have not been directly validated in brain tumors. Our purpose was to compare estimates of forward leakage K-trans derived from DCE-MRI to the estimates K obtained using [C-14] aminoisobutyric acid quantitative autoradiography ([C-14] AIB QAR), an established method of evaluating blood - tumor barrier permeability. Both DCE- MRI and [C-14] AIB QAR were performed in five rats 9 to 11 days following tumor implantation. K trans in the tumor was estimated from DCE- MRI using the threeparameter general kinetic model and a measured vascular input function. Ki was estimated from QAR data using regions of interest (ROI) closely corresponding to those used to estimate K trans. K trans and Ki correlated with each other for two independent sets of central tumor ROI (R = 0.905, P =.035; R = 0.933, P =.021). In an additional six rats, K trans was estimated on two occasions to show reproducibility (intraclass coefficient = 0.9993; coefficient of variance = 6.07%). In vivo blood - tumor permeability parameters derived from DCE-MRI are reproducible and correlate with the gold standard for quantifying blood tumor barrier permeability, [C-14] AIB QAR.