- Magnetic Resonance Imaging
- Cerebral MRI
- MR of the Brain
- Nuclear Magnetic Resonance
- MRA (MR Angiography), looking specifically at the blood vessels of brain
What is it?
- A way of imaging the inside of your head, including the brain, its covering layers, its blood supply and the fluid that bathes it.
- There are no X-rays, and therefore no danger of irradiation.
- It uses a large magnet to image your head while you lie on a bed with your head in the centre of a large tunnel.
What is it commonly used for?
- Seizures/ fits/ epilepsy
- Infection/ meningitis
- Possible tumours
- Cerebral palsy or other neurological birth abnormalities
- Other conditions affecting the brain
How should I prepare?
- Try to remember or check with your physician if you have had any surgery involving a metal implant, e.g. a pacemaker, aneurysm clips or a cochlear implant (hearing aid). Also any history of trauma to the eye involving metallic fragments should be stated. This is because some metal objects will be affected by the magnet and may be moved. They could also interfere with the scan and result in poor image quality.
- Remember to remove: dentures, glasses, coins, credit cards, cell phones, keys and any other metal objects (hair clips, belts, etc.) for the same reason.
- In small children where sedation / anaesthesia may be administered, the child should not eat or drink anything 4-6 hours prior to procedure (check with each department; usually children under 6).
How is it performed/ how will the patient experience it?
- This is a relatively long procedure: 30 to 90 min.
- You will have to wear a hospital gown (to avoid magnetic interference from zips, metal buttons, etc.)
- The MR scanner is a large electromagnet with a central tunnel, into which the table (on which you will be lying) moves. This means you will be completely encased by the scanner for the duration of the study, unlike CT where the scanner is just a ring.
- In addition you may have a plastic cover (called a coil) placed over your head to improve the images.
- You will have to lie very still with small rest gaps between sequences to avoid the effects of movement on image quality.
- The scans are very noisy and for this earplugs or headphones with music will be provided.
- You may need to have a dye injected into your veins (this means a needle in the arm).
What are the risks?
- There are no radiation risks.
- Injury may occur from an inadvertent metallic object in the scanner.
- Risk of a pacemaker malfunctioning or previous surgical implants (e.g. aneurysm clip) moving due to the magnetic field.
- Heating of metallic plates (e.g. orthopaedic implants for old fractures).
- Low risk of a condition called nephrogenic systemic fibrosis with thickening of skin and kidney damage as a reaction to certain contrast media (the dye that is injected). This is very rare.
- Claustrophobia due to the confined space and the length of the study (there is usually an alarm bell so that you can get out quickly).
What are the limitations of the procedures?
- It is currently the best way of looking at the brain
- Requires anaesthesia in small children
- Poor at seeing calcification and bone disease
- Still misses certain diseases
- Still subject to radiological interpretation
- Many disease processes resemble each other, even on MRI.