Design. Patients will undergo serial brain MRIs with gadolinium-based contrast agent on both 3- and 7-tesla scanners over an approximate 25-week period. 3-tesla scans will be obtained at baseline and week 25. 7-tesla scans will be obtained at baseline and at weeks 13 and 25. Participants with one or more centripetal/rim-enhancing lesions at the baseline scan will be randomized and followed. Clinical evaluation and blood testing will be performed at baseline and weeks 13 and 25.