Dynamic contrast-enhanced MR imaging was used to measure the kinetics of enhancement in three different animal
tumor models (Walker 256, R3230 AC, MCF7) using three different Gd complexes (Gd-DTPA, Gd-DTPA-24-cascade-polymer 30 kD, and polylysine-Gd-DTPA 50 kD). The three
tumor models varied in growth rate, with the most rapid growth demonstrated by Walker 256 cells and the slowest growth occurring in the MCF7 cells. For each
tumor, the kinetics of enhancement using
polylysine-Gd-DTPA was analyzed using a pharmacokinetic model to estimate the vascular volume of the
tumor. The rate of entry of the
contrast agent into the interstitial space served as the measure of vascular permeability. The smallest molecular-weight agent,
Gd-DTPA, could not provide information about vascular permeability. The intermediate and the largest agents both demonstrated that the faster-growing Walker 256
tumor had greater vascular permeability than did the slower-growing R3230 AC
tumor. The degree of vascular permeability in the MCF7
tumor could not be assessed fairly due to insufficient statistics. The current study provides evidence supporting the hypothesis that more rapidly growing
tumors have higher vascular permeability than do
tumors that grow more slowly.