Noninvasive assessment of the functional neovasculature in 9L-glioma growing in rat brain by dynamic H-1 magnetic resonance imaging of gadolinium uptake

Pathophysiologic parameters of the functional neovasculature and the blood- brain barrier of 9L-glioma in rat brain were measured noninvasively by dyna mic H-1 magnetic resonance imaging studies of gadolinium (Gd)-DTPA uptake C hanges of apparent [Gd-DTPA] uptake in time (C-T[t]) were analyzed in a sli ce through the center of 10 9L-gliomas using fast T-1 measurements. The dis tribution of the contrast agent was spatially correlated with the distribut ion of perfused microvessels as determined by immunohistochemical analysis. This method permits a distinction between perfused and nonperfused microve ssels with a disrupted blood-brain barrier. In transverse slices of the who le tumor, a spatial correlation was observed between C-T maps and the two-d imensional distribution of perfused microvessels. In the next step, Gd-DTPA uptake rates were spatially related to the perfused microvessel density (N -P) or vascular surface area (S-P). In tumor voxels with perfused microvess els, a linear correlation was found between Gd-DTPA uptake rate constants ( k values) and N-P or S-P. No correlation was observed between k values and the total microvessel density. These are the first data that show a relatio n between Gd-DTPA uptake rates and parameters of the functional neovasculat ure in 9L-glioma growing in rat brain. Now that Gd-DTPA uptake studies can be related to parameters of the functional neovasculature, they may be used more efficiently as a prognostic tool before or during therapy.