Feraheme (ferumoxytol) is FDA-approved for iron supplementation and is composed of iron oxide nanoparticles classified among the ultra-small superparamagnetic iron oxides (USPIO). In this project we hypothesize that Feraheme could become a sensitive and specific marker of active inflammation in multiple sclerosis. We will explore this hypothesis taking advantage of ultra high field strength (7T) MRI to further increase the effectiveness of the contrast agent Feraheme at revealing inflammatory activity.