The most annoying metallic objects were hairpins. We would get old ladies with more hairpins than hairs! And they'd always leave a few in, so when we did the scout images we'd see a big black hole where there should have been a brain. Taking them out on the table is very risky, because it's so easy for them to slip out of your hand...and if they get loose and fly into the scanner, you have to go in and find them.

We were always very careful...it's easier to get a patient killed than you'll ever know. When a piece of metal gets loose near the magnet, it seeks out the center of the magnet, which happens to be where the patient's head is. And the bigger the object, the stronger the pull is. We've had hospital stretchers stuck to the magnet...if you try to jerk them off it too fast, you can cause the magnet windings to torque, which can cause a quick build-up of heat (relative to the near-absolute zero temperature in the magnet). At that point, the magnet can "quench", i.e., to boil-off all the cryogenic helium inside it. The liquid helium turns to gas and bursts from the magnet, displacing the oxygen in the room in the process. If you don't get a door open quickly, you could suffocate. We were trained to drop to the floor if this happens, as the helium is lighter than air.

Bet you didn't know that one.

Mostly, metal in the scanner is a nuisance; it confounds the technologist and makes the scan a real hassle. People with dental implants (me), or worse, braces, make brain imaging very difficult to perform. The biggest worry are metallic implants like aneurysm clips in the brain. Just moving a patient into the magnet can cause them to twist - even if they're not ferromagnetic! Eddy currents created by moving any metal through the magnetic field (basic electrophysics) can affect the implants.

The funniest thing I ever saw in my radiology days was in the emergency room (actually, there are about 100 funniest things I ever saw in the emergency room). But this one stood out...I had to x-ray a patient's abdomen (called a KUB), and when I walked in he was running around the perimeter of the room. In discomfort. I got him to lie down and took an x-ray..went to develop it and saw a slender tube-like, air-filled structure. I didn't know what the heck it was, this cylinder of air...then, I noticed a small spring at one end, like the little old spring inside the average ball point pen. I found out later (from an OR tech) that it was a bottle of Vitalis Super-Hold hair gel with the convenient pump-action nozzle...somehow (and for some reason) inserted into his rectum.

You can't make this stuff up.