Comparison of gadomer-17 and gadopentetate dimeglumine for differentiation of benign from malignant breast tumors with MR imaging

This study compared gadopentetate dimeglumine (molecular weight, 0.5 kD), a standard contrast medium, and Gadomer-17 (apparent molecular weight, approximately 35 kD), a new, clinically applicable, large-molecular contrast medium, with respect to their microvascular characterizations of experimentally induced breast tumors at magnetic resonance (MR) imaging. A spectrum of breast tumors, benign through highly malignant, was induced in Sprague-Dawley rats ( n = 30) by intraperitoneal administration of N-ethyl- N-nitrosurea (ENU), a potent carcinogen. All animals underwent three-dimensional spoiled gradient-recalled MR imaging, with precontrast imaging and dynamic postcontrast imaging after injection of gadopentetate dimeglumine (0.1 mmol/kg) and Gadomer-17 (0.03 mmol/kg), administered in a random order at a 24-hour interval. Several microvascular parameters were compared: the endothelial transfer coefficient ( K PS), a measure of microvascular permeability; the fractional plasma volume (fPV), and the plasma equivalent volume. Each MR imaging parameter was correlated with histopathologic findings. With Gadomer-17, the mean values for K PS and fPV were significantly greater in carcinomas than in fibroadenomas ( P < .004 and .04, respectively). With gadopentetate dimeglumine, the mean values for fPV and PEV were significantly greater in carcinomas ( P < .004 and .02, respectively). Because of the high variability within both fibroadenoma and carcinoma groups, however, there were no significant correlations between K PS, fPV, or PEV and histopathologic tumor grade as indicated by the Scarff-Bloom-Richardson score, for either agent. Although the K PS and fPV estimates obtained from dynamic MR imaging data with Gadomer-17 enhancement offer some potential for characterizing breast tumors, none of the quantitative microvascular parameters derived with either agent were significantly correlated with histopathologic tumor grade.