MRI stands for magnetic resonance imaging. An MRI scan uses strong magnetic fields and radio waves to produce detailed images of the inside of your body. They can be used to diagnose conditions, plan treatments and determine how well an existing treatment plan is working.
Almost any part of the body can be MRI scanned, including:
- internal organs
- brain and spinal cord
- blood vessels
- bones and joints
The MRI scanner is a large cylinder that contains powerful magnets. During the scan you lie inside the cylinder on a sliding couch that moves your whole body into the scanner. Depending which part of you is being scanned you will enter the scanner feet first or head first.
During the scan you will hear loud tapping noises. This is the electric current in the scanner coils being turned on and off. Your radiographer will give you headphones or earplugs to wear before the scan begins and you may also be able to listen to music to help you relax. Ask about bringing your own CD.
The radiographer will control the scanner from an adjacent room. Although you won’t be able to see them, you will be able to talk to each other via an intercom and the radiographer will be able to see you at all times on the TV monitor.
MRI scans are safe and painless however some people can find it claustrophobic to be inside the scanner. Your radiographer will be able to reassure you throughout and give you instructions to help you remain calm. You can also be given a sedative if you need it, this will usually need to be prescribed in advance by your GP. It is important to remain as still as possible during the scan to enable the radiographer to obtain clear images.
An MRI scan does not expose your body to radiation which means that it is safer than other types of scan and can be used on pregnant women and babies, if necessary. However, it is not suitable for everyone. If you have a pacemaker fitted to control an irregular heartbeat, your radiographer may advise against having an MRI or the scan may need to be performed in a specific hospital rather than your preferred centre. It is important that you let the radiographer know of any implants or surgery you may have had, or if there is a chance you may have fragments of metal in your eyes. If you are at all concerned, please talk to the radiographer beforehand.
MRI scans are broken down into different “sequences”. Each sequence lasts no more than a few minutes, however the whole procedure typically last between 15 minutes and an hour and a half depending on the area the radiographer needs to scan and how many sequences are required.
With most MRI scans, you will be able to eat and drink as normal on the day of your scan, unless your appointment letter advises otherwise. Some scans require you to drink plenty of water beforehand while others will ask you to avoid eating or drinking anything for up to four hours before your appointment. Always check your appointment letter for any special instructions.
Immediately before your scan you will be asked to remove any metal objects from your body such as jewellery, piercings, dentures and hearing aids, as well as any clothes with metal zips, fasteners or buttons.
Depending which area is being scanned you may be injected with a dye that will show tissues and blood vessels in greater detail. Tell your doctor beforehand if you have severe kidney disease or if you experience blood-clotting problems. The dye can cause organ damage in rare cases and you may need to undergo pre-scan tests to check your suitability before being injected.
If you have taken a sedative you will need to ask someone to drive you home afterwards. Young children and babies may be given a general anaesthetic, as it is important for them to stay still during the scan.
You will normal be able to resume your normal activities immediately after having an MRI scan, however you will need someone to drive you home if you had a sedative and they will need to remain with you until the sedative wears off. You should receive your results soon after the scan.