The purpose of this study is to evaluate how well various types of magnetic resonance imaging (MRI) machines and their settings can find problems in the brain. An MRI machine takes pictures of organs and structures in the body. It does this using a magnetic field and pulses of radio wave energy. Researchers want to compare how sensitive each machine is in detecting an imaging signature of chronic inflammation in the brains of patients with multiple sclerosis (MS). This includes looking at various brands of machines and the strength of their magnets. If successful, the study will provide information to improve the diagnosis and treatment of people with MS. Participants will be people who are thought to have MS (in the opinion of the study doctor) or who are healthy volunteers.