Multiple Sclerosis and the MRI: What is an MRI? How does an MRI work? What is meant by a “MRI with contrast?” These and other important MRI fundamentals are discussed.

The MRI stands for Magnetic Resonance Imaging and it's the most useful biomarker currently [2018] available to diagnose MS, monitor disease progression, and assess response to disease modifying therapies. Let's discuss the basics:

What is an MRI?
MRI stands for Magnetic Resonance Imaging. The MRI machine is essentially a really big magnet that can take detailed pictures of fat and water. This is fantastic for brain and spinal cord imaging, because of central nervous system is made up of different types of fats and water!

How Does the MRI Work?
The MRI machine uses a giant magnet is used to send out pulses of radio waves. These waves make the protons found in water molecules within the tissues of the brain become “excited” and “stand up at attention.” Then when the radio pulse is turned off, those excited protons “relax” and slowly fall back down. Different neural tissues cause different “relaxation times,” which result different contrasts between the structures of the brain.
Important safety points: The MRI uses a magnet and has NO radiation and NO X-rays

What is an MRI with Contrast?
The contrast dye is called gadolinium. It is injected into your vein partway during MRI. This dye stays in blood stream and lights up blood vessels. The dye can’t cross the blood brain barrier (BBB) so it doesn’t leak out into the brain tissue. If, however a brain with MS experiences new active inflammation, the BBB becomes “irritated” and gets leaky, allowing the contrast dye to leak out. This results in a gadolinium enhancing lesion.

MRI Basics:
-Scanner Strength: measured in units of Tesla. For MS, you want a 1.5T or 3T scanner. NO, a 0.7T open MRI isn’t ok.
-slice thickness: ideally 3mm or thinner.
-Gap between slices: ideally NO gap.
-Sequences for brain: FLAIR SAG, FLAIR AXIAL, T2 AXIAL, T1 PRE CONTRAST AXIAL, T1 POST CONTRAST AXIAL

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