WHAT IS MRI?
MRI [Magnetic Resonance Imaging] uses a powerful magnet, which produces a strong magnetic field to generate diagnostic images.
The magnetic field forces hydrogen protons in the body to align with that field. When an external radiofrequency pulse is then applied, the protons are stimulated, and spin out of equilibrium, no longer aligned with the the magnetic field.
When the radiofrequency field is turned off, the MRI sensors are able to detect the energy released as the protons realign with the magnetic field. The time it takes for the protons to realign with the magnetic field, as well as the amount of energy released, changes depending on the environment and the chemical nature of the molecules.
Radiologists are able to tell the difference between various types of normal or tissues based on these magnetic properties.
WHAT ARE THE INDICATIONS FOR MRI?
MRI scanners are particularly well suited to image the non-bony parts or soft tissues of the body. They differ from computed tomography (CT), in that they do not use the damaging ionizing radiation of x-rays.
The brain, spinal cord and nerves, as well as muscles, ligaments, and tendons are seen much more clearly with MRI than with regular x-rays and CT.
In the brain, MRI can differentiate between white matter and grey matter and can also be used to diagnose infections and tumours. Because MRI does not use x-rays or other radiation, it is the imaging modality of choice when frequent imaging is required for diagnosis or therapy, especially in the brain.
