Spatial colocalization of VCAM-1 and VCAM-MPIO–induced hypointensities in metastasis and medulloblastoma models. Representative images from a MDA231Br-GFP tumor-bearing animal (A–F) and a DAOY medulloblastoma animal (G–L). Positive VCAM-1 expression (brown) is evident on the endothelium of vessels at the margins of both the MDA231Br-GFP tumor (A and D) and the DAOY tumor (G and J); cresyl violet counterstain (blue). Scale bar = 1 mm. Inset images in A and G illustrate presence of VCAM-MPIO beads (black arrowhead) bound to the luminal surface of VCAM-1–positive vessels (brown); scale bar = 10 μm. B, E, H, and K, Corresponding high-powered magnification images from boxes; scale bar = 100 µm. D, E, J, and K, Areas segmented as VCAM-1 positive are highlighted in red. Note, in A and D nonspecific staining of the ventricles and tissue edges is evident, which has not been removed from the analysis for transparency, but does not reflect true endothelial VCAM-1 staining. C, F, I, and L, Corresponding T2*-weighted MRI slices showing VCAM-MPIO–induced hypointensities either alone (C and I), or with an overlay (red) showing perspective transformed histology derived VCAM-1 staining (F and L); scale bar = 1 mm.