MRI scans of the brain. Photograph: NHS
MRI scans are safe and generally most people are able to use them. However, some patients are recommended not to use MRI. These patients usually have medical devices in their bodies, which the MRI scanner's powerful magnets can interfere with. Some of these devices are:
- a drug pump - delivers painkilling medication directly to an area of the body
- a pacemaker - electrical device which controls irregular heartbeats
- a nerve stimulator - electrical implant that treats nerve pain
- a cochlea implant - similar to a hearing aid, but surgically implanted in the air
In some cases (though in many it is not possible), it is safe for some patient's with pacemakers and implanted defibrillators if certain procedures are followed. This usually involves a cardiologist (heart specialist) making the device MRI-safe. During the procedure they will also monitor the patient's heart rhythm.
MRI may also not be recommended for patients who have:
- metallic fragments - usually if they are near the eyes or any blood vessels
- prosthetic metal heart valves
- penile implants
- brain aneurysm clips - used to seal blood vessels in the brain
- an intrauterine device (IUD) - a plastic contraceptive device in the womb
Some patients with tattoos also need to tell the Radiographer if their tattoo contains any traces of metal, and also during their procedure if they feel any discomfort or heat on the tattoo's area.
Although MRI scans are suggested to pose no risk to pregnant women, as a precaution, women who are three months pregnant are not recommended to undergo an MRI scan.