Tumor microvasculature observed using different contrast agents: a comparison between Gd-DTPA-Albumin and B-22956/1 in an experimental model of mammary carcinoma.

OBJECTIVE: The aim of this study was to compare a pure macromolecular contrast agent (Gd-DTPA-albumin) with a new protein-binding blood pool contrast agent (B22956/1) in terms of their capacity to investigate the microvasculature in an experimental model of mammary carcinoma. MATERIALS AND METHODS: Tumors were induced by subcutaneous injection of 5 x 10(5) BB1 cells into the backs of 5-7 week-old female FVB/neuNT233 mice. The animals were observed using DCE-MRI when the longest diameter of the tumor was 10.2+/-2.0 mm. DCE-MRI experiments were carried out using B22956/1 and (24 h later) Gd-DTPA-albumin. RESULTS: DCE-MRI data showed that vasculature in the tumor rim was characterized by greater fractional plasma volume and transendothelial permeability than vasculature in the tumor core as measured by both contrast agents. Permeability to Gd-DTPA-albumin in the tumor core was hardly measurable while permeability to B22956/1 was substantial. Histologically the tumor core showed areas of well vascularized, viable tissue surrounded by necrotic regions. CONCLUSIONS: DCE-MRI experiments performed with B22956/1 are useful in the investigation of vasculature in those tumor regions that are characterized by low permeability to macromolecules.