This factsheet is for people who are having a magnetic resonance imaging (MRI) scan, or who would like information about it.
An MRI scan uses magnets and radiowaves to produce detailed images of the inside of the body. It can help to diagnose and monitor many different medical conditions.
You will meet the health professional carrying out your procedure to discuss your care. It may differ from what is described here as it will be designed to meet your individual needs. Details of the procedure may also vary from country to country.
Publication date: October 2010
About MRI scans
About MRI scans
About MRI scans
An MRI scan uses radiowaves and a magnetic field to create images of the inside of your body. The images that an MRI scanner takes are very detailed. They are taken in thin 'slices' through your body and can be taken from any direction. They show your bones, soft tissues such as muscle, skin, nerves and blood vessels, and organs such as your brain and heart. An MRI scanner can take pictures of most parts of your body.
Because an MRI scanner takes very detailed pictures of the body, it can often show things that aren't seen on an X-ray or in other tests such as an ultrasound.
You may have an MRI scan to find out the cause of symptoms such as pain, joint or muscle stiffness, swelling or weight loss. You may also have an MRI scan if you have been diagnosed with a condition such as cancer, where your doctor needs detailed information so you can make decisions about what treatment is best.
Who can not have MRI scans
Not everyone can have an MRI scan. The magnetic field from the scan affects some metals and can cause any metal inside your body to move. This is why it's important to tell your radiographer (radiologic technologist; a health professional trained to perform imaging procedures) if you have any metal in your body. The kinds of metal you might have in your body include:
- heart pacemaker, metal valve or defibrillator (a device that keeps your heart rhythm regular)
- an inner ear hearing aid (cochlear implant)
- aneurysm clip (a metal clip on an artery)
- joint replacements or large metal implants
- an intra-uterine contraceptive device or coil
- shrapnel or gunshot wounds
- a body piercing
- metal fragments anywhere in your body
- some medication patches
- tattoos that have been done using a metallic ink
Not all metals are affected by the scanner, for example some artificial joints like hips and knees aren't magnetic. Metal stitches or shrapnel pieces that have been inside your body for a long time may also not be affected by the scanner.
If you're pregnant then you wouldn't usually be offered an MRI scan, particularly in the first three months of pregnancy, unless it's absolutely necessary. If you are, or think you might be pregnant, tell your radiographer before your MRI appointment.
What are the alternatives
Other investigations that produce images of the inside of your body include the following:
- X-ray. An X-ray uses radiation to produce an image.
- Ultrasound. This uses sound waves to produce an image.
- Computerised tomography (CT) scan. This is a test that uses X-rays to create three-dimensional images of part of your body.