In vivo axial gradient recalled echo MR images and corresponding H&E-stained sections from a prior study . The magnetic resonance (MR) images and H&E-stained sections represent different orientations, as each MR image represents only one cross-sectional slice through the mammary gland while the histologic sections show the entire gland. During imaging, the mammary glands are attached to the skin of the mouse, and are therefore wrapped around the body of the mouse. For excision, the glands are peeled back from the body of the mouse and laid flat, so that coronal H&E-stained sections can be obtained. We used an agar grid (a polyethylene mesh embedded in partially deuterated agar) to register the axial MR images with the H&E-stained sections. (a) Normal mammary gland, with intramammary lymph node, (b) lymph node and mammary intraepithelial neoplasia (MIN), (c) lymph node and small tumor. For each MR image, the display field of view is approximately 2.0 × 2.0 cm, and in-plane resolution is 117 microns.