1) The study investigated the uptake of SPIO (superparamagnetic iron oxide), an MRI contrast agent, by periadventitial fat in an atherosclerosis mouse model. 2) Results showed significantly greater uptake of iron in the periadventitial fat of apoE k/o mice compared to control mice, as measured by iron particles and area. 3) Preliminary evidence also suggests uptake of iron in the periadventitial fat of atherosclerotic rabbits and humans, suggesting macrophage-like activity in this tissue that warrants further investigation into its role in atherosclerosis and imaging.