Please Don't Feed the MRI Machines

from the animal-magnetism dept

As magnetic-resonance imaging scanners have become more commonplace and the power of their magnets has increased, the machines are getting hungry and sucking in all kinds of stuff — floor polishers, wheelchairs and medical equipment are some of the more mundane things, with the New York Times saying a sprinkler repairman’s acetylene tank was sucked into one, causing a fire that burned down a building. In another case, a policeman’s gun was sucked out of its holster and fired a shot when it hit the machine. MRI magnets are never off, even when the power is cut, because they draw power from supercooled helium, though one company is working on a new generation of scanners that only attract ferromagnetic metals like iron, nickel and cobalt. Observers say the biggest cause of problems is inattentive staff. Apparently these magnets attract morons as well. Update: The NYT’s corrected the original story to clarify that MRIs “are cooled by liquid helium to eliminate electrical resistance so that their magnetic fields persist indefinitely, not powered by liquid helium.” The second error was my own: the company is indeed working on detectors that are only sensitive to ferromagnetic metals.

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Comments on “Please Don't Feed the MRI Machines”

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Danielle says:

Re: No Subject Given

very common thinking. Even some doctors in our hospital try to walk in with stethoscopes and other metal, thinking the magnet is only on when we’re scanning. I’ve heard of many cleaners that come in after hours to polish the floor and assume the magnet is off. Luckily we’ve never had any incidents in our scan room (YET!!).

Chris Maresca (user link) says:

CERN and magnets

I once spent a week at CERN ( where they have HUGE magnets that control plasma in an attempt to create fusion. When they first started using it, they had a huge problem with left-behind tools flying through the air when they turned them on (no threat to anyone as they flood the area with nitrogen before firing it up), but you can imagine what might happen when the thing is fully operational with plasma inside.

The solution was to build a bunch of titanium (non-magnetic) tools, which was very, very hard and expensive to machine at the time. So CERN engineered a new way of machining titanum, which has since lead to machined titanium things being relatively cheaply available to consumers (watches, rings, etc.).


TJ says:

No Subject Given

The linked article has a correction at the end of page two about the helium. It is used to cool the magnets, not power them. Good to see since I didn’t understand how liquid helium would help power a magnetic field.

Boy the idea that a small sliver of metal in their body blinded a patient gives me pause about having an MRI. A metal shaving penetrated one of my eyes when I was younger, and doctors said it was best not to try to remove it. Hadn’t thought before now that it might blind me later during a medical test. Yeesh.

Hopefully T ray technology will advance sooner than later and help replace these useful yet occasionally dangerous MRI systems.

dorpus says:


“MRI magnets are never off, even when the power is cut, because they draw power from supercooled helium, “

Correction: the article says the magnets, which are superconductors, will stop being so strong once the helium is drained. It does take a few minutes to release the helium, and a sudden release can cause problems also, e.g. the clinic whose roof blew off when supercold helium blasted into the atmosphere.

“though one company is working on a new generation of scanners that only attract ferromagnetic metals like iron, nickel and cobalt.”

When you say “scanner”, I assume you mean the walk-through scanners at the entrance to the clinic which detect ferromagnetic metals. You can’t make MRI magnets that “only attract ferromagnetic metals”.

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