In vivo mapping of spontaneous mammary tumors in transgenic mice using MRI and Ultrasonography.

To compare T1- or T2-weighted magnetic resonance imaging (MRI) and ultrasonography (US) as tools for in vivo mapping of different tissue components in spontaneous tumors of transgenic mice. Materials and Methods: Human-like mammary adenocarcinomas from FVB/neuT transgenic mice were analyzed by T2-weighted and T1-weighted MRI at 4.7 Tesla and US and then, after excision, were paraffin-embedded for histologic analysis. The histologic samples were prepared taking care to obtain sections that spatially matched the MRI and US images as precisely as possible. Results: US can obtain basic information such as the size of developing tumors in experimental animals and can identify necrotic areas. T2-weighted MRI, especially if compared to T1-weighted MRI and/or US, allows advanced analysis of morphologic aspects, with high resolution in the differentiation of details of necrotic areas such as coagulation, liquefaction, biphasic splitting of cysts, and fibrotic and lipidic infiltration. Conclusion: Of the three methods, T2-weighted MRI provides the most information about the anatomy of tumors. However, when distinctions between the different types of necrosis are not needed, US analysis is to be preferred for its practicality