Mammary carcinoma model: Correlation of macromolecular contrast-enhanced MR imaging characterizations of tumor microvasculature and histologic capillary density

PURPOSE: To determine the relationship between capillary density, a recognized surrogate of tumor angiogenesis, and magnetic resonance (MR) imaging-derived estimates of plasma volume (PV) and microvascular permeability in two mammary carcinoma models. MATERIALS AND METHODS: Dynamic spin-echo imaging was performed by using albumin-(gadolinium-diethylenetriaminepentaacetic acid)(34), a prototype blood-pool contrast medium, in 14 rats with a subcutaneously implanted slow- or fast-growing subtype of R3230 mammary carcinoma. Data were fitted to an established two-compartment kinetic model to estimate PV and permeability. RESULTS: MR imaging-derived tumor PVs and permeabilities increased exponentially with increasing capillary density. MR imaging-derived microvascular characteristics correlated strongly with histologic capillary density, with an r(2) of .85. CONCLUSION: Contrast medium-enhanced MR imaging may prove useful in estimating angiogenic activity in carcinomas. MR imaging may be superior to histologic assay because it is noninvasive, can be used to ''sample'' the entire tumor, and reflects both anatomic and physiologic characteristics.