Understanding MRI
Magnetic resonance imaging (MRI) is the diagnostic tool that offers the most sensitive, non-invasive way of imaging the brain, spinal cord and other areas of the body.
1. MRI scanner; 2. Magnet; 3. Radio frequency coil; 4. Patient table
In people with MS, the immune system attacks the protective covering of the nerves, (known as myelin) causing inflammation and damage. The specific sites of damage are called lesions. MRI scans are used to visualize the lesions caused by MS, which show up as white or dark grey plaques.
MRI is the preferred imaging method to help establish a diagnosis of MS and monitor the course of the disease.
How it works
Unlike a conventional x-ray, MRI doesn’t use radiation. Instead it uses magnetic fields and radio waves to measure water content in tissues – regular and abnormal.
- A very strong magnetic field causes a small percentage of the hydrogen protons in water molecules to line up in the direction of the magnetic field.
- Once the protons have lined up, radio waves and additional weaker magnetic fields are used to knock them out of line.
- When the radio waves are stopped, the protons relax back into line. As they relax, the protons release resonance signals that are transmitted to a computer.
Types of MRI scans
The types of MRI used – most commonly T1- and T2-weighted scans – measure resonance in different ways.
