Posted on 11/12/2014 3:53:06 PM PST by steve86
Should’ve used aluminum tanks...
That level is what I dealt with in school, but now I work with K Volts.
Seems to me there is a giant red emergency stop button on the machine. Was there no one in the hospital that had a clue how to shut it down?
Were you certain the gauss lines extended outside of the room itself? Depending on the size of the room containing the MRI the 1 or even 3 gauss lines may have been contained entirely in the room. Hence your instructions to stay out :)
I was present in a magnetic facility where a trained assistant, not paying attention to what he was doing, accidentally rolled (upright rolling) a tank of co2 a little too close to one of the magnets. Which then promptly decided ‘he’ wanted said tank of co2. Fortunately for the tech, the facility was staffed at that time of day and his shout brought 4 grown men, quickly, to help him deprive the magnet of the goody. And it took effort for the 5 grown men to do this. I watched and learned. Physics’ll kill ya.
I wonder if there was more than one MRI in this particular facility with nested fields. That might explain the delay in shutoff.
Here's a research lab quenching their superconducting magnet when they were taking out of service. (Warning: this was filmed in ShakyVision): http://www.youtube.com/watch?v=9SOUJP5dFEg
You should try an “open” MRI center if you have to do it again. In an open MRI there are 2 flat magnets, 1 above you and 1 below. It’s like you’re the meat in a sandwich. I had one done in July and I fell asleep.
CC
I read the article and saw that. You still would think they would have a manual release valve, for just this reason.
Don’t really know. I was inspecting the trailer for moisture and related environmental issues. Nobody else was present, so I carefully followed instructions to stay out of the MRI room. :)
That's the prequel to the youtube video I posted in #45. I was wondering why there was a chair stuck to the front of the MRI.
That’s white man’s law. Meant to keep the minorities down...
OK, I see why you might not want to push the Red Button. Whoa...
They deactivated the field....they had to ramp it down without blowing the burst disks in He recirculation system. If the liquid heluim had been released they were dead within minutes ( the helium will displace the oxygen in the room and will adsorb through the skin to reach the leve of the room....and ramping it down took a couple of hours to do properly without popping the disks.
We had a local sheriff deputy who entered the magnet field (1 Gauss line which is marked) with his service weapon while dealing with a prisoner. it pulled the pistol right out of his holster. We didn’t ramp it down to get it out....we used a come-along winch to extract it rather than ramp it down.
Just had to bring ol’ Max into this, eh?
Did no one consider they could just turn off the power?
Yes, it will probably compromise the cooling of the superconducting magnet, but they wouldn’t have had to wait for 4 hours.
The Gentle Giant shoulda spent more time concentrating on his physics lessons when younger....
Once you get the electricity flowing through the superconducting magnet it keeps on flowing (thus the superconducting part of it). If you shut down the power the magnet stays on until it warms up enough to lose its superconductivity. The big red button should have used that current to boil off the liquid helium quickly, but the button didn't work.
I’m surprised that the disturbance to the field by all the metal in the gas cylinder didn’t lead to a quench on its own.
I once saw a slow quench on a research magnetic (of an NMR spectrometer, which has a somewhat different design and field geometry relative to an MRI) that was caused just by a student bringing a chair with a metal back close to the housing of the liquid nitrogen dewar that makes up the outer jacket of these sorts of things.
Even with a slow quench, the enormous volumes of nitrogen gas and helium gas that vent from those suckers is really impressive - and we knew enough to clear the room as the oxygen was steadily being displaced.
Most importantly, in a facility with as many random workers as one would find in a hospital, there should have been clear and prominent warnings that no metal objects are allowed in the room - surely they had to have pacemaker warnings on all the entrances if they’re at all competent.
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