In article , ( says...

Hey, I just had an MRI done yesterday. I spent some time talking with the
people there and learned several neat things. First of all, if you have ever
made metal chips or gotten a face full of rust from under a car, you need to
tell them. They will take x-rays of your head to see if you have any loose
fragments in there. Um... yeah... Ok, the only place a metal sliver is a
problem is in the eyes. If you have one elsewhere in the body, the scar
tissue that forms around it will hold it in place. The same holds true for
surgical staples, etc. They still want to know about them, but they can work
around them. Metal slivers in the eye will be encapsulated (so they don't
irritate things) but no scar tissue ever forms on it, so it is mobile. The
magnet can move this around and the concern is that it will damage the
retina or optic nerve. Implants and such are usually secured well enough
that they aren't worried about them tearing loose, only distorting the
images. Small ferrous objects that make it into the room aren't usually a
problem if they are not loose (they didn't have a problem with the rivets in
my jeans or the metal lugs on my shoes. Presumably, they are well secured
enough and small enough to not shoot across the room). For the most part,
non-ferrous is fine so long as it isn't in the magnet with you (distorts the
image) but ferrous is a no-no. The bigger it is or the less it is secured to
something, the worse the situation. A steel rivet on a belt, not a problem,
an unsecured side arm in a persons hand, big problem. An artificial hip that
is well healed, probably not a problem as it is well secured to you and you
are fairly massive (and well secured to the table).

My niece was in a bad car crash last year and fractured a number of
vertebrae. Before they could do the MRIs needed to image the area
before surgery, they had to do an endoscopy on her first. She
had swallowed her tongue stud. That would have been a problem in
the magnetic field, apparently.

Jim


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