Originally posted by: jagec
Originally posted by: robphelan
If the possibility of magnets in the abdomen exists, magnetic resonance imaging (MRI) must be avoided. An MRI machine would literally rip the magnet out of the body through the belly.
:Q
That applies to pretty much any decent sized chunk of metal...MRI machines create an appallingly strong magnetic field.
An MRI almost certainly would not rip the magnet through anything, but that's not to say it wouldn't cause some form of injury - the forces generated by an MRI magnet on metal objects are large, but they're not usually large enough to rip through flesh (unless the object is unusually sharp, or anchored in some way - e.g. a piercing). The concern is more that if the metal object is in a sensitive area, it may pull on a delicate organ (e.g. the eye, where any movement could cause bleeding into the eye leading to permanent blindness).
This is definitely the case in the abdomen, where a swallowed magnetic object could be pulled with sufficient force to tear some blood vessels and cause internal bleeding, or possibly, though I think this unlikely, enough to tear the intestinal wall.
Firmly attached metal objects - e.g. joint replacements, spinal rods to hold a broken back, etc. are all fine for MRI as they're firmly attached and won't move. Even shrapnel injuries aren't really a problem, as they tend to be lodged in muscle or bone, and won't move in these tough tissues. The main problem with metal objects is that if they're near the bid being scanned, they ruin the picture - especially if they're ferromagnetic. Modern implants tend to be made of titanium, which isn't feromagnetic, which causes minimal problems.