Fig 1: MR and histology images from mice with 4T1‐GFP brain metastases. (A) Representative postgadolinium T1‐weighted images from two different mice, injected with either VCAM‐MPIO or IgG‐MPIO, demonstrating contrast enhancement in the tumour‐bearing striatum. (B–C) Representative pre‐MPIO (B) and post‐MPIO (C) MGE3D images in mice imaged with either VCAM‐MPIO or IgG‐MPIO. (D) Quantitation of MPIO‐induced hypointense voxels, presented as post‐contrast minus pre‐contrast for ipsilateral and contralateral hemispheres in each individual animal. Bars indicate mean. (E) Histology images showing Prussian blue staining from the same animals post‐MRI, and corresponding to the regions in red squares in (C), respectively; the location of apparent MPIO‐laden macrophages corresponds to hypointense regions in the precontrast MGE3D images (B). Scale bar = 100 μm. (F) In mice imaged with VCAM‐MPIO, specific endothelial binding of individual VCAM‐MPIO (arrows) to VCAM‐1 positive blood vessels (brown) can be seen. Scale bar = 10 μm. MGE3D, multigradient echo three‐dimensional; MPIO, microparticles of iron oxide. VCAM‐1, vascular cellular adhesion molecule 1.