A very strong magnet
An MRI works with a permanent magnetic field. A pacemaker, some implants or metal fragments can move, heat up or stop working properly. The questionnaire is there to know before the exam.
What happens if you tick a box
Your request isn't refused: it is held, the time is kept, and a radiologist reviews your file. Many recent implants are compatible under conditions; the radiologist then chooses a suitable protocol.
On the day
Bring your implant card if you have one. Remove jewellery, your watch and any metal objects. If you are claustrophobic, say so: the team explains each step and stays in contact during the exam.