TUMOR CHARACTERIZATION WITH DYNAMIC CONTRAST-ENHANCED MRI USING MR CONTRAST AGENTS OF VARIOUS MOLECULAR-WEIGHTS

Dynamic contrast-enhanced MR imaging was used to measure the kinetics of enhancement in three different animal tumor models (Walker 256, R32 30 AC, MCF7) using three different Gd complexes (Gd-DTPA, Gd-DTPA-24-c ascade-polymer 30 kD, and polylysine-Gd-DTPA 50 kD). The three tumor m odels varied in growth rate, with the most rapid growth demonstrated b y 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 vo lume of the tumor. The rate of entry of the contrast agent into the in terstitial space served as the measure of vascular permeability. The s mallest 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 assess ed fairly due to insufficient statistics. The current study provides e vidence supporting the hypothesis that more rapidly growing tumors hav e higher vascular permeability than do tumors that grow more slowly.