• Question: what happens if someone has a magnetic object in their body during an MRI

    Asked by daniel roberts to Andy on 21 Jun 2015.
    • Photo: Andrew Scott

      Andrew Scott answered on 21 Jun 2015:

      Hi Daniel,

      We ask people to remove any metal objects from their pockets and take clothes with metal fasteners off. Some people can have metal inside their bodies put there during surgery or during an accident. There are 3 possible problems:

      1. The metal could move in the magnetic field causing harm to the patient. This is a particular worry for people who might have metal in their eyes from metalwork accidents. Most metal parts used in surgery won’t move when they have been there for a few months and are safe.

      2. The metal can absorb the radiowaves that we use and get hot, causing internal burns. Implants used in surgery are tested to make sure that they don’t get hot.

      3. The metal objects change the magnet field around them and change the way the pictures appear. It’s usually quite easy to tell when someone has a metal object inside them on the scan as the pictures have what look like holes in them around the metal object. If the object is near the bit of the body that we’re interested in, this can be a big problem.

      Magnets are just magnetised bits of iron and I don’t think the problems with magnets are much different to the problems with bits of iron. Cochlear implants used to help some patients who have hearing trouble often contain magnets and some patients with these can be scanned now.

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