RT Journal Article SR Electronic T1 MR imaging in acute multiple sclerosis: ringlike appearance in plaques suggesting the presence of paramagnetic free radicals. JF American Journal of Neuroradiology JO Am. J. Neuroradiol. FD American Society of Neuroradiology SP 1544 OP 1546 VO 13 IS 6 A1 T Powell A1 J G Sussman A1 G A Davies-Jones YR 1992 UL http://www.ajnr.org/content/13/6/1544.abstract AB MR studies in three patients with multiple sclerosis have shown clearly defined rings within plaques of demyelination, having signal characteristics consistent with the presence of paramagnetic material. It is suggested that these appearances represent the presence of free radicals in the macrophage layer forming the margin of an acute plaque.