OT - Stuff that flew into MRI magnets

A buddy of mine did is graduate work in high energy particle physics in the early 70's at LBL (that's Lawrence Berkley Labs).

The magnets they had there made yer average MRI look like a kids toy.

Even those guys who KNEW what the hell they were doing (or thought they did) would suck some pretty nasty things in everyonce and a while.

Usually on the first time a new mag was powered up.

One of my best memories was an afternoon I spent with him 'playing around'... I vividly remember him giving me a 4 inch long 1 inch diameter piece of aluminum rod, having me put in between the pole pieces of a (pretty wimpy by their standards) magnet and having him energize it. He had me hold it in the middle of the poles, pretty close to the top one and about 2 inches off the bottom one.... The he said let go.. it just hung there, suspended in air... it was moving down, but so slowly you couldn't see it... The Eddy currents it generated as a conductor in a mag field kept it suspended.... Then he told me to take it out... No way..... What was interesting was you could feel it moving ever so slowly the way you tried to drag it, but the harder you pulled the harder it pulled back....

Dave

What about the fillings in your teeth?

Yup. At GE in the MRI manufacturing bays, most of the systems don't have full screen rooms, they just have aluminum "end caps" on the ends of the magnet, to contain the RF so as not to interfere with the other

30 or so scanners in the building. The doors are about 24"x24" aluminum, and the eddy current effect is amazing at 1.5T on a door that size. Great isometric exercise, opening that sucker up 30 times a shift. And yes, the harder you pull it, the harder it pulls back.

It was fun to show this off using a half-dollar coin - falling lengthwise in the magnet, took several seconds. Falling crosswise (not cutting flux lines but passing through them) it falls normally. Even more evident with an empty aluminum soda can. There were a few...unauthorized experiments...from time to time as well. GE has a great magnet safety training video showing the standard 8" crecent wrench flying up to the front of the magnet, where there was a concrete block (in front of plywood) at the face of the magnet. Shattered the concrete block. Damned impressive, and probably lots of fun to make.

Dave Hinz

Nope, those aren't magnetic, nor do they have enough radius for the eddy-current effect to be noticable. FWIW, metal slivers (Ha! metal content!) don't come out either, although they do twitch around uncomfortably as they align themselves to the magnetic force lines. Steel toed shoes will get your attention when you walk in front of the magnet, but not to the point of them picking your feet up or anything. You wouldn't want to go into one if you had a history of metal slivers in your eyes, though.

Dave Hinz

They X-rayed my eye sockets to be sure there were no slivers that might rip out / through my eyes . Ken Cutt

Well, they wouldn't rip out through anywhere - there isn't enough gradient in the force to make it move - it's strong but very very very even (measured in parts per billion, or the imaging wouldn't work) so it would just align them very straight with the long axis of your body. If that's not the angle it's at to start, that'd be the not-fun part.

We never lost a wrench into the magnet, but we did have a guy lose one of those round metal stepstools into one - the "library" type which you step on and it stops, get off and it rolls - that kind. We had fiberglass ones around the magnets, but the assembly folks had steel ones because those "never" got near the magnets.

Well, the inevitable happened. "Wild Bill" (who would say 3 words to you during the typical week) came over and said "I just did something really stupid." Wow. 6 words. 2 weeks quota, this should be interesting... it took 5 or 6 of us to get that stepstool out of the magnet, because ramping it down and back up would have taken all shift, and quenching it would have been a few grand worth of helium. I don't even want to think how many work and workplace rules we were violating...

Dave "Hypothetically, that is. Wasn't me, can't prove it, and it's more than 7 years ago anyway. Didn't happen in Bay 8B, nope, never did. Wasn't Wild Bill either, nor was I even there when it happened. Didn't happen, I mean." Hinz

That probably makes sense. Later in that same video is the same wrench with a straing gage, showing 80 pounds of force on that little wrench. So maybe more than 22g.

Yup, kid in New York got killed by a tragic chain of failures resulting in a steel O2 cylinder hitting him while in the magnet.

Well, that's hardly the technology's fault, though. Talk to your lawmakers.

Hm, I only know of one fatality of that nature, a kid in New York. Could this be a different one, or a distortion of the same incident, I wonder? Not saying it's impossible or even implausible, just that I hadn't heard of a second one.

Boy, that one picture showing the base and seat of an office desk chair sucked into the magnet (and two legs sticking out pointed up) sure looks like a "Photoshop Moment" to me... That or two of those 'rubber leg and foot' deals you hang out the car door on Halloween Night.

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Well they got me through it safely , :-) . Which is what counts . Surprised me how noisy it was though even wearing ear plugs . Ken Cutt

Bruce

Those are pretty hefty magnets. There was an incident here in Seattle that an inmate went in for an MRI and the magnet stripped the accompanying officer of his weapon, cuffs and misc. other iron. Scared hell out of everyone to see a service revolver leap through the air. Being well trained he had the safety on, but I still wouldn't want to be there. My granddad lost part of a toe to a malfunctioning safety on a shotgun.

Jim

I'm heartened to hear that our convicts are getting first-class medical attention.

A revolver with a safety? Didn't know any officers carried those.

Makes sense, though, if you know that the coil you're inside has lots of current at audio frequencies, going through coils of wire in a strong magnetic field. In other words, a big speaker. I've, um, heard (see previous disclaimer) that if you take, say, Dark Side of the Moon and pipe it into the analog input of, for instance, the Techron 8603 gradient amplifiers, hypothetically of course etc, that it sounds really cool when you lay in the bore and listen to it. So I've, er, heard.

Well, there are actions with transfer bars and others with hammer blocks. However, they are both always "on" unless the trigger is fully depressed.

Pete Keillor

Safety on a service revolver?

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

Yeah, you'll find it on the left, a couple inches under the Redfield

3-10x50 scope mounted on a 2" barreled Taurus compact 45ACP stainless ported 5-shot, Gunner. ;)

(CDNN volume 2005-3, catalog pages 13 and 73, respectively.)

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