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. As the MRI scanner produces strong magnetic fields, it's important to remove any metal objects from your body, including:
- watches
- jewellery, such as earrings and necklaces
- piercings, such as ear, nipple and nose rings
- dentures (false teeth)
- hearing aids
- wigs (some wigs contain traces of metal)
Inaddition metal implants or metal fragments needs to be noted . Some examples of metal implants or fragments include:
- a pacemaker – an electrical device used to control an irregular heartbeat
- an implantable cardioverter-defibrillator (ICD) –a similar device to a pacemaker that uses electrical shocks to regulate heartbeats
- metal plates, wires, screws or rods – used during surgery for bone fractures
- a nerve stimulator –an electrical implant used to treat long-term nerve pain
- a cochlear implant –a device similar to a hearing aid that's surgically implanted inside the ear
- a drug pump implant –used to treat long-term pain by delivering painkilling medication directly to an area of the body, such as the lower back
- brain aneurysm clips –small metal clips used to seal blood vessels in the brain that would otherwise be at risk of rupturing (bursting)
- metallic fragments in or near your eyes or blood vessels (common in people who do welding or metalwork for a living)
- prosthetic (artificial) metal heart valves
- penile implants –used to treat erectile dysfunction (impotence)
- eye implants –such as small metal clips used to hold the retina in place
- an intrauterine device (IUD)–a contraceptive device made of plastic and copper that fits inside the womb
- artificial joints – such as those used for a hip replacement or knee replacement
- dental fillings and bridges
- tubal ligation clips –used in female sterilisation
- surgical clips or staples – used to close wounds after an operation
- Tattoos, some tattoo ink contains traces of metal, but most tattoos are safe in an MRI scanner. Tell the radiographer immediately if you feel any discomfort or heat in your tattoo 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
- breasts
- heart and blood vessels
- internal organs, such as the liver, womb or prostate gland.
Some MRI scans involve having an injection of contrast dye. This makes certain tissues and blood vessels show up more clearly and in greater detail.
It's possible for contrast dye to cause tissue and organ damage in people with severe kidney disease. If you have a history of kidney disease, you may be given a blood test to determine how well your kidneys are functioning and whether it's safe to proceed with the scan.
You should also let the staff know if you have a history of allergic reactions or any blood clotting problems before having the injection.
During an MRI scan, you lie on a flat bed that's moved into the scanner. Depending on the part of your body being scanned, you'll 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 imaging investigations. 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'll be able to talk to the radiographer through an intercom and they'll 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'll be given earplugs or headphones to wear.
It's very important to keep as still as possible during your MRI scan. The scan lasts 15 to 90 minutes, depending on the size of the area being scanned and how many images are taken.
Magnetic resonance imaging (MRI) is very safe and most people can have the procedure, including pregnant women and babies.
However, there are some instances where an MRI scan may not be recommended, because the strong magnets used during the scan can affect any metal implants or fragments in your body.
Before having an MRI scan, you should tell medical staff if:
- you think you have any metal in your body
- you're pregnant or breastfeeding
There's no evidence to suggest MRI scans pose a risk during pregnancy. However, as a precaution, MRI scans aren't usually recommended during pregnancy, particularly in the first three months
Hope this helps for those undergoing an MRI.