If you have multiple sclerosis (MS), you probably had several tests done before you received your diagnosis.

There isn’t one test to diagnosis MS, so testing can vary. Doctors can use neurological exams, information about previous symptoms, blood tests, and spinal fluid tests.

A magnetic resonance imaging (MRI) scan isn’t used to diagnose MS but rather to rule out other diseases. A diagnosis of MS requires more information than what a scan alone can give.

By looking at more than one test or exam result, doctors can get a clearer picture of what’s going on in your body.

An MRI provides cross-sectional images of tissue from anywhere in the body. Unlike other scanning or traditional X-ray machines, an MRI doesn’t use any radiation.

Doctors use an MRI to detect bleeding, swelling, and other abnormalities. The scan can also be used for assessing structural damage.

An MRI works by using the natural magnetic properties of the body, which are found in hydrogen atoms. Inside the hydrogen atom is a proton. Protons are sensitive to any magnetic field.

During the procedure, the machine takes an image when hydrogen molecules in the body align because of the magnetic pull of the MRI. The scan shows what’s going on in various organs and structures in the body.

The image is usually very detailed, making it easy for doctors to see any problems or changes. If you have MS, small lesions are often visible in the brain and/or spinal cord.

To help diagnose MS, MRIs that show any abnormalities in the brain or spinal cord are closely looked at. Doctors can use the initial MRI scan by comparing it to any follow-up scans to see how the disease is progressing.

There’s no set standard for how often you should have an MRI. But according to the National MS Society, most doctors suggest yearly exams.

If possible, it’s also suggested that you have the scans done on the same scanner from one exam to the next to make comparing the scans easier.

In general, the two most common types of scans that can be used for an initial MS diagnosis and for additional follow-ups are these:

  • T1-weighted: This MRI scan of the brain uses an intravenously injected fluid to help doctors see lesions more clearly. The fluid helps to spotlight areas that have inflammation. Dark spots can also be detected. It’s believed that these dark spots may show areas of permanent damage to the nerves.
  • T2-weighted: Images from this type of scan can tell doctors about new and old wounds in the tissue.

Some people with MS get an MRI only to find that there’s nothing on the image.

According to the National MS Society, about 5 percent of people with MS show no initial signs of the disease on an MRI. These people are clinically diagnosed with MS by their doctor, who can still confirm a diagnosis based on other tests.

If you’ve been diagnosed with MS and haven’t had an MRI in the past year, contact your doctor. Learning how fast your MS is advancing can help determine how to proceed with treatment.

There may be better ways of dealing with medication, exercise, and adaptive devices. Being proactive can better prepare you for the future.