MRI is considered the best way to help diagnose MS. However, 5% of people with MS do not have abnormalities detected on MRI; thus, a negative scan does not completely rule out MS. In addition, some common changes of aging may look like MS on a MRI.
You would also need the technology to track the progress of disease. Although they aren't widely needed, people with MS may get repeat scans to determine the status of their disease and how well their medications are working.