Magnetic resonance imaging (MRI) is very safe and most people can have the procedure, including pregnant women and babies.
Medical devices
However, the strong magnets that are used during MRI can interfere with certain medical devices that are implanted in the body. Therefore, an MRI scan may not be recommended if you have:
- a pacemaker: an electrical device that is used to control an irregular heartbeat
- an implantable cardioverter-defibrillator (ICD): a similar device to a pacemaker that uses electrical shocks to regulate heartbeats
- a nerve stimulator: an electrical implant that is used to treat long-term nerve pain
- a cochlea implant: a device that is similar to a hearing aid but is surgically implanted inside the ear
- a drug pump: used to treat long-term pain by delivering painkilling medication directly to an area of the body such as the lower back
In some cases, it is safe for people with pacemakers and implanted defibrillators to have MRI scans if certain procedures are followed.
Before the scan, a cardiologist (heart specialist) or another trained healthcare professional will need to make your pacemaker or defibrillator MRI-safe.
They will also need to carefully monitor your heart rhythm during the procedure. However, in many situations this is not possible and alternatives to MRI may be necessary.
MRI may also be unsuitable for people who have:
- brain aneurysm clips: small metal clips that are 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
- prosthetic (artificial) metal heart valves
- penile implants: used to treat erectile dysfunction (impotence)
- eye implants: such as small metal clips that are used to hold the retina in place
It may be possible for you to have a scan even if you have brain aneurysm clips in place. This will need to be considered on an individual basis.
You must tell the radiographer if you have an intrauterine device (IUD) fitted, although it is not likely to prevent you having an MRI scan. A IUD is a contraceptive device made of plastic or copper that fits inside the womb.
If you're unsure whether or not you have metal fragments in your body, for example, from metalwork or welding, you will need to have an X-ray to confirm whether this is the case.
MRI is usually suitable for people with:
- artificial joints, such as those who have had a hip replacement or knee replacement
- dental fillings and bridges
- tubal ligation clips, which are used in female sterilisation (an operation that permanently prevents a woman from being able to get pregnant)
- surgical clips or staples
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 to your tattoo.
Pregnancy
There is no evidence to suggest that MRI scans pose a risk during pregnancy. However, as a precaution, scanning is not usually recommended during the first three months of pregnancy.
