Why screening is taken so seriously
An MRI scanner's magnet is permanently on. It can pull ferromagnetic objects across a room, and it can interfere with electronic implants. Almost every MRI safety incident traces back to something that was not declared before the scan. The questionnaire you fill in is the main safeguard, and completing it thoroughly is the most useful thing you can do.
Always declare these
- Cardiac devices — pacemakers, implantable defibrillators and loop recorders. Many modern devices are MRI-conditional, but each needs specific settings and supervision.
- Neurostimulators — deep brain, spinal cord and vagus nerve stimulators.
- Cochlear implants and bone-anchored hearing aids.
- Infusion and insulin pumps, and continuous glucose monitors.
- Aneurysm clips and coils, stents, heart valves and embolisation devices.
- Orthopaedic metalwork — plates, screws, prostheses and spinal rods. These are usually safe, but can distort nearby images.
- Metal fragments — shrapnel, or metal splinters in or near the eye from grinding or welding work.
- Surgery within the last six weeks, and any implant you are unsure about.
If you have an implant card, bring it. The make and model let the department check the manufacturer's MRI conditions instead of cancelling the appointment.
Also worth mentioning
- Pregnancy — MRI is used in pregnancy where needed, but the indication is reviewed and contrast is generally avoided.
- Breastfeeding — you can usually continue as normal after contrast; ask the department for their current advice.
- Kidney problems — reduced kidney function affects whether and which contrast agent is used, and a recent blood test may be requested.
- Previous contrast reaction — any reaction to gadolinium or to iodinated contrast.
- Claustrophobia or difficulty lying flat — raise it when booking rather than on the day, so the clinic can plan a wide-bore slot or sedation.
- Tattoos and permanent make-up — older or cosmetic pigments can contain metal and may feel warm.
Leave in the changing room
Jewellery, watches, hairpins, glasses, hearing aids, dentures containing metal, removable piercings, keys, cards with magnetic strips, phones, and clothing with zips, hooks or metallic thread. Some medication patches contain metal foil and have to be removed, so mention any patch you are wearing.
What safety screening does not mean
A long list of questions is not a sign that MRI is dangerous. For patients without contraindications it is one of the safest imaging examinations available, with no radiation dose. The screening exists precisely so that the small number of genuine risks are identified before you enter the room.
If anything on your questionnaire is uncertain, say so rather than guessing. The radiographer would far rather spend ten minutes checking an implant than discover it afterwards.