Pharmacokinetic parameters in CNS Gd-DTPA enhanced MR imaging

Dynamic MR imaging can be used to study tissue perfusion and vascular permeability. In the present article a procedure for dynamic MR is presented, which (a) accurately resolves the fast kinetics of tissue response during and after intravenous infusion of the paramagnetic contrast medium Gd-DTPA and (b) yields a linear relationship between the measured MR signal and the Gd-DTPA concentration in the tissue. According to these features, the measured signal-time curves can be analyzed within the framework of pharmacokinetic modeling. Tissue response has been parameterized using a linear two-compartment open model, with only negligible effects of the peripheral compartment on the central compartment. The three model parameters were fitted to the signal-time data pixel by pixel, based on a set of 64 rapid SE images (SE 100/10 ms, image scan time 13 s, interscan intervals 11 s). This makes it possible to construct parameter images, whereby structures become visible that cannot be distinguished in conventional Gd-DTPA enhanced MR. As a clinical example, the approach is discussed in a case of glioblastoma.