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 [¹⁴C] aminoisobutyric acid quantitative autoradiography ([ ¹⁴C]AIB QAR), an established method of evaluating blood-tumor barrier permeability. Both DCE-MRI and [¹⁴C]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 three-parameter general kinetic model and a measured vascular input function. K_i was estimated from QAR data using regions of interest (ROI) closely corresponding to those used to estimate K^trans. K^trans and K_i 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, [¹⁴C]AIB QAR.