Magnetic resonance imaging (MRI) is a type of scan that uses strong magnetic fields and radio waves to produce detailed images of the inside of the body.
An MRI scanner is a large tube that contains powerful magnets. You lie inside the tube during the scan.
An MRI scan can be used to examine almost any part of the body, including the:
- brain and spinal cord
- bones and joints
- heart and blood vessels
- internal organs, such as the liver, womb or prostate gland
The results of an MRI scan can be used to help diagnose conditions, plan treatments and assess how effective previous treatment has been.
Read more about how MRI scans work.
What happens during an MRI scan?
During an MRI scan, you lie on a flat bed that is moved into the scanner. Depending on the part of your body being scanned, you will be moved into the scanner either head first or feet first.
The MRI scanner is operated by a radiographer, who is trained in carrying out X-rays and similar procedures. They control the scanner using a computer, which is in a different room to keep it away from the magnetic field generated by the scanner.
You will be able to talk to the radiographer through an intercom and they will be able to see you on a television monitor throughout the scan.
At certain times during the scan, the scanner will make loud tapping noises. This is the electric current in the scanner coils being turned on and off. You will be given earplugs or headphones to wear.
It is very important that you keep as still as possible during your MRI scan. The scan will last between 15 and 90 minutes, depending on the size of the area being scanned and how many images are taken.
Read more about how an MRI scan is performed.
An MRI scan is a painless and safe procedure. You may find it uncomfortable if you have claustrophobia (fear of enclosed spaces), but most people find this manageable with support from the radiographer. Sometimes going into the scanner feet first may be easier, although this is not always possible.
MRI scans do not involve exposing the body to X-ray radiation. This means people who may be particularly vulnerable to the effects of radiation, such as pregnant women and babies, can use them if necessary.
However, not everyone can have an MRI scan. For example, they are not always possible for people who have certain types of implants fitted, such as a pacemaker (a battery-operated device that helps control an irregular heartbeat).
Extensive research has been carried out into whether the magnetic fields and radio waves used during MRI scans could pose a risk to the human body. No evidence has been found to suggest that there is a risk, which means that MRI is one of the safest medical procedures currently available.
Read more about who can and can't have an MRI scan.