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

Rationale and Objectives. This study compared gadopentetate dimeglumine (mo lecular weight, 0.5 kD), a standard contrast medium, and Gadomer-17 (appare nt molecular weight, approximately 35 kD), a new, clinically applicable, la rge-molecular contrast medium, with respect to their microvascular characte rizations of experimentally induced breast tumors at magnetic resonance (MR ) imaging. Materials and Methods. A spectrum of breast tumors, benign through highly m alignant, was induced in Sprague-Dawley rats (n = 30) by intraperitoneal ad ministration of N-ethyl-N-nitrosurea (ENU), a potent carcinogen. All animal s underwent three-dimensional spoiled gradient-recalled MR imaging, with pr econtrast imaging and dynamic postcontrast imaging after injection of gadop entetate dimeglumine (0.1 mmol/kg) and Gadomer-17 (0.03 mmol/kg), administe red in a random order at a 24-hour interval. Several microvascular paramete rs were compared: the endothelial transfer coefficient (K-PS), a measure of microvascular permeability; the fractional plasma volume (fPV), and the pl asma equivalent volume. Each MR imaging parameter was correlated with histo pathologic findings. Results. With Gadomer-17, the mean values for K-PS and fPV were significant ly greater in carcinomas than in fibroadenomas (P < .004 and .04, respectiv ely). With gadopentetate dimeglumine, the mean values for fPV and PEV were significantly greater in carcinomas (P < .004 and .02, respectively). Becau se of the high variability within both fibroadenoma and carcinoma groups, h owever, there were no significant correlations between K-PS, fPV, or PEV an d histopathologic tumor grade as indicated by the Scarff-Bloom-Richardson s core, for either agent. Conclusion. Although the K-PS and fPV estimates obtained from dynamic MR im aging data with Gadomer-17 enhancement offer some potential for characteriz ing breast tumors, none of the quantitative microvascular parameters derive d with either agent were significantly correlated with histopathologic tumo r grade.