Pharmacokinetic Modeling of Gd-DTPA Extravasation in Brain Tumors

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Abstract
Lüdemann L, Wurm R, Zimmer C. Pharmacokinetic modeling of Gd-DTPA extravasation in brain tumors. Invest Radiol 2002;37:562–570. Rationale and Objectives. The endothelial permeability of brain tumors affecting the blood-brain barrier can be quantified using dynamic contrast enhanced MR imaging. Materials and Methods. The dynamics of contrast medium (CM) exchange was investigated in 31 brain tumors (intra- and extra-axial) by fast repeated T1-weighted imaging in order to determine the exchange rates and saturation concentrations. Results. The analysis of CM exchange reveals two different transport processes from the blood into two separate interstitial subcompartments for intra- and extra-axial tumors, a rapid one with a transfer constant of 1/ kf=7.0 seconds and a slow one with 1/ ks=133.7 seconds. Highly significant differences exhibit gliomas and meningiomas with respect to the saturation concentrations of fast and slowly enhancing compartments. Conclusions. The fast component is probably caused by extravasation into viable tissue (enhanced in meningiomas) while the slow one probably reflects increased diffusion distances into poorly perfused tissue such as necrotic areas in glioblastomas.