Heterogeneity of Multiple Sclerosis White Matter Lesions Detected With T2*-Weighted Imaging at 7.0 Tesla

Background and purpose: Postmortem studies in multiple sclerosis (MS) indicate that in some white matter lesions (WM-Ls), iron is detectable with T2*-weighted (T2*-w), and its reciprocal R2* relaxation rate, magnetic resonance imaging (MRI) at 7.0 Tesla (7T). This iron appears as a hyperintense rim in R2* images surrounding a hypointense core. We describe how this observation relates to clinical/radiological characteristics of patients, in vivo.

Methods: We imaged 16 MS patients using 3T and 7T scanners. WM-Ls were identified on T1-w / T2-w 3T-MRIs. Thereafter, WM-Ls with a rim of elevated R2* at 7T were counted and compared to their appearance on conventional MRIs.

Results: We counted 36 WM-Ls presenting a rim of elevated R2* in 10 patients. Twenty-three (64%) lesions coincided with focal WM-Ls on T2-w MRIs; 13 (36%) coincided with only portions of larger lesions on T2-w images; and 20 (56%) corresponded to a hypointense chronic black hole. WM-Ls presenting a rim of elevated R2* were seen in both relapsing-remitting patients with low disability and in those with long-standing secondary progressive MS.

Conclusions: WM-Ls with a contour of high R2* are present at different MS stages, potentially representing differences in the contribution of iron in MS disease evolution.