I sometimes volunteer at a local detention facility, and they have a metal detector. Last night I was up there and hadn't had time to change out of my work clothes, and I triggered the metal detector even with no metal on my person whatsover. The guy running the wand asked me if I happened to work in a machine shop and I said yes, and he said work jeans from a machine shop or steel fab shop can trigger a scanner no problem.
I would have never guessed. Turned out this particular officer used to be a machinist, and he had specific knowledge on the subject.
And if you go to get an MRI - our bodies might have metal flecks within. Be sure to mention it - as the metal gets hot and burns.
Martin
Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder
Grant Erw> I sometimes volunteer at a local detention facility, and they have a
I had to get a cat scan of my eyes before the MRI. They said the magnet could drag any metal chips through my eyeball. Ouch. It was interesting that my non-ferrous wedding ring moved with sound of the thing. ERS
No, it doesn't get hot or burn. (I worked in engineering on MRI scanners for ~12 years). It can cause image distortion localized around the metal (very local effect for slivers, nearly invisible). If you've got metal in your eyes, they may choose not to use MRI on you, though.
I'd be happy to discuss this in as much detail as you'd like.
You and I really need to sit down somewhere and have a beer or three, Iggy. email me your address again, I'll lend you my (only) copy of GE's Magnet Safety videotape.
Thanks Dave... We need to get together for a beer indeed... If you wanna sell my bearings, I give you a 50% commission on them. That is, I want to be paid 45% of the closing price (that 45% figures in your listing and paypal costs). You charge buyers a fair amount for shipping. That's my offer. It expires in 1 week from now. Picking up those bearings would be a good excuse to meet and have a beer and watch that GE safety video.
I have had several MRIs done over the years. Last one was last week, and was the 3 Tesla variety, the latest and strongest MRI.
As with all, I checked the boxes where they asked if I welded or worked with metal.
They were very concerned over my heart stent, but went ahead with the MRI when they saw that the stent did not appear on a chest x ray, meaning it had been removed during my heart surgery, or it was not metal.
But, I figured they would do x rays of my head because of the welding/metalworking history. They didn't.
One of the tekkies said that the magnets caused metal to spin or be pulled out of the body. He demonstrated how powerful it was by giving me a metal object. I held it up at arms length about ten feet from the MRI, and it felt like I was trying to twist a very stuck door knob.
Anyway, that's my MRI story. I go on the 8th for results. It was a brain scan, and I hope they find some functioning tissue.
my silver alloy wedding ring jumped around when i was in the mri tube last, but the Ti plate in my neck didn't seem to move around, although they were worried about it some when i told them i had one.
Thanks. A very scary and fascinating story. A little below was a mention of a police officer's handgun pulled out of his hands and accidentally firing -- of interest to you due to your sentiments related to guns.
The tekkie in question should stick to pushing buttons, because he's not qualified to describe the physics involved.
The force on an object, at a given distance, is proportional to it's mass. First, he shouldn't be bringing ferrous objects into the scan room, ever, for any reason. Second, he shouldn't be telling people that metal could "spin or be pulled out of the body" because it's complete and utter horseshit.
Well, sure. It aligns with the flux lines of the field. Just like a tiny little metal sliver...only thousands of times more forcefully.
That is another example of a scan tech who doesn't understand their technology. Titaniaum hand tools are what we use when _working on/in_ the magnets. I'm curious about your ring - does a magnet stick to it? Could the moving around have been, instead, a _reluctance_ to move in the field? A subtle difference.
One fun trick with an MRI magnet - get an empty soda can. Hold it up right on two fingertips, and let it tip. If you're tipping the length of the bore, it'll take maybe 5 seconds to tip over. If you go across the bore, it'll fall over normally. The magnetic field is inducing eddy currents in the can if it falls in a way that changes which flux lines it's cutting (the long way) which gives you that resistance to movement. Same effect with a coin on edge, tipped over. LOTS of force (resistance to movement) on a 2'x2' aluminum door on the test systems - those don't get a full screen room, you just enclose the bore on both ends. The trapdoor, when the magnet is down, takes a good 5-10 seconds to open, and it doesn't matter much how hard you pull on the sucker, it moves at it's own speed. Really fun when you open the door on a magnet that's not at field, you nearly fall on your ass because there's not the resistance you expect...
well, i'm not sure it's pure Ti, nor the screws used to hold it to the bone. on an xray, the screws look like 1" fine thread drywall screws.
no, a magnet, even a super magnet doesn't stick to the ring. i thought it was reluctance too, as it seemed to try to lineup a certain way in the tube. it almost had enough force to move my finger if i relaxed my hand. do the force lines move in an mri? i wondered if they'd generate eddy currents in the ring at the time.
a neat trick: suspend a large horseshoe magnet on a string centered over an Al plate that is on a low friction turntable. rotating the magnet will cause the Al plate to rotate.
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