- Baseline evaluation: Participants have four magnetic resonance imaging (MRI) scans over a 3-month period to assess disease activity. For the MRI scans, the patient lies on a table that slides into the scanner - a narrow metal cylinder with a strong magnetic field. Scanning time varies from 20 minutes to 3 hours, with most scans lasting between 45 and 90 minutes. Only patients with activity at or above a certain level are eligible to continue with the treatment phase of the study.