Magnetic Resonance Imaging (MRI) is a painless scanning technique which uses magnetic fields and radio waves to create images of tissues, organs and other structures inside your body.
These can be acquired in any orientation within the body and can produce images of any specified body part. MRI does not use x-rays and has no known harmful effects.
The images may be useful in diagnosing illness or in helping your doctor plan appropriate treatment for you.
What is an MRI scan used for?
MRI scans may be useful for the following conditions:
- Brain and spinal cord conditions
- Tumours, cysts and other anomalies in parts of the body
- Joint injuries; including knee, shoulder and back
- Liver disease and other organs in the abdomen; including gallbladder
- Investigating pelvic pain in women.
Can everyone have an MRI scan?
An MRI scan has many benefits but it isn’t suitable for everyone. The magnetic field from an MRI scanner affects some metals, including those used for surgical clips or pins. So if you’ve had surgery which left metals inside your body, it’s important to tell your radiographer.
The magnetic field from the MRI may also affect electronic implants such as pacemakers. This may mean the devices don’t work properly or may heat up, which could be dangerous. You cannot usually have an MRI scan if you have:
- A heart pacemaker or defibrillator (a device that keeps your heart rhythm regular)
- An inner-ear hearing aid (cochlear implant)
- An aneurysm clip (a metal clip on an artery in your brain).
How do I prepare for an MRI scan?
Before having an MRI scan, you should be able to eat, drink and take any medicines as usual. At the centre, your radiographer will ask you to complete and sign a safety questionnaire.
Before you go into the scanning room, you’ll probably be asked to undress down to your underwear and put on a hospital gown. If you’re wearing an underwired bra, you may need to remove this too, as the underwiring usually contains metal. You’ll also need to remove any jewellery (including piercings) or metal objects such as hairclips, your watch or dentures with metal parts. You may need to remove your glasses and hearing aids if you wear them. You may also need to remove your make up, especially eye make up, which can contain metal fibres.
What happens during an MRI scan?
Your radiographer will ask you to lie on your back on a table. The table slides into the cylinder-shaped MRI scanner, which contains the magnet. Your position may be adjusted using foam pads or straps. This will also help you to stay still. Your radiographer will make sure you’re comfortable and any equipment around you is in a safe place.
You will be given a buzzer to hold and your radiographer can see and hear you at all times and will be able to talk to you using an intercom. You will hear loud mechanical noises during the scan so you will be given earplugs and/or headphones to wear during your MRI scan.
How long will it take?
You can expect to lie still for between 20 minutes and one hour, depending on how much of your body is being scanned.