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Pistol stuck to MRI machine.
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Previously:
https://www.homemadetools.net/forum/...377#post154543
https://www.homemadetools.net/forum/...393#post188963
https://www.homemadetools.net/forum/...955#post171679
https://www.homemadetools.net/forum/...9129#post88721
SO I'm guessing there was no way to simply turn the machine off?
There is a button to quench the magnets in an emergency, but it takes weeks to put the machine back in service.Quote:
Originally Posted by Frank S
Quenching the magnet is only done in emergencies, it is possible to damage the magnet that way. Normally it is ramped down slowly. There was once a situation in one of our accounts that a custodian went into the magnet room with a floor polisher (the entrance is clearly marked "Danger Strong Magnetic Field) and of course the magnet quickly ripped it from his hands. The GE magnet suffered cosmetic damage but was ramped down to remove the offending appendage, then ramped back up when the ramping power supply arrived.
Thanks, the only MRI machines I have ever seen were in a scrap yard and they were dead as hammers with broken handlesQuote:
Originally Posted by Elizabeth Greene
The docs. wanted to put me in one of those machines in 87 when part of a dozer blade I was working on fell on me causing a compression fracture in my T12. But changed their mind once they x rayed and noticed the piece of old shrapnel encased in scar tissue right next to my heart
Sooo exactly how did the handgun get into the MRI room in the first place? I have had a couple of MRIs and before I get near the machine I am checked for anything that might interfere with the magnet, or results...
Working in a hospital for over 25 years, the most likely scenario would be a prisoner ( who had to have the handcuffs removed to enter MRI), caused a situation requiring immediate attention by the attending officerQuote:
Originally Posted by Nick79
Yeah you do not want to get an MRI if you have a sliver of steel in your finger, or your eye. MRI machines are part of the reason that Helium is in short supply.
Rather less wasteful than party balloons though... Disposable Helium cylinders for balloon inflation have become popular for suicide by asphyxiation, another good reason to stop selling them!
„Party balloons” are filled with a „leftover” helium from MRI - not „fresh” one.
Still a waste, we have a Helium recovery and repurification plant that runs 24/365 to capture and recycle Helium used, as in an MRI scanner, for superconducting magnet cooling, one of my jobs is topping up and and recovery of Helium in some of those units. Many of the cylinder suppliers here use the same grade of Helium as they sell for other industrial uses for 'balloon gas', recovered or "left-over" Helium gets fed into their bulk supply for all uses once cleaned up.Quote:
Originally Posted by 12L14
Well this is interesting reading . I was not aware of these facts.
Specifically the last section on that page; (bold added my me)
How Does An MRI Machine Use Helium
An MRI machine contains coils, a magnet and wires that conduct current. The machine uses a great deal of energy because of its large magnetic field. In order for it to use that much energy, it must be super conductive. For this to occur, wires inside the machine need to be reduced to a temperature of near zero degrees. The machine requires a substance in order for it to maintain a cold temperature, and that substance is liquid helium. The wires continuously are doused with liquid helium. The fluid has a temperature of -269.1 degrees Celsius, which is the equivalent of -452.11 Fahrenheit. The average MRI machine utilizes 1,700 liters of helium. A standard 18″ balloon requires about .1 oz of helium, and the machine uses about 56,100 oz to give you a mental picture of how much helium that is. The amount of helium in the scanner must be topped off on a regular basis, which increases the amount of helium used by the machine even further.
Unfortunately, the amount of helium on earth is diminishing due to its heavy usage, and it floating away. There isn’t much of it on earth because it’s not weighed down to the atmosphere. It’s slowly, but continuously, floating off into space. The noble gas is unable to be synthesized and is usually made through natural radioactive decay. Once the helium is gone, it’s gone forever because it’s a nonrenewable resource. The medical field requires a large quantity of helium to assist patients with diagnosing and monitoring their condition, which is by far a vital and valued use.
Advancing technology can eventually decrease the use of liquid helium to achieve superconductivity. There are already room temperature superconductors, albeit at extreme pressures too high to be practical...
https://www.unlv.edu/news/release/lo...om-temperature
There are many superconductors...
https://en.wikipedia.org/wiki/List_of_superconductors
The engineering tradeoffs include more than the temperature needed to go super. If a superconductor is exposed to too high a magnetic field it will crash. This effect limits the amount of current a superconducting wire in an electromagnet can carry.
I'm reasonably confident that we'll be able to build an MRI in the next decade or two that can operate on liquid nitrogen temperatures.
Yes but also mostly no. The US decided to decommission the national helium reserve in the mid 90s, so they basically flooded the market with cheap helium. So for 20 years the price of helium was artificially depressed, which skewed the economics of projects that required helium. Now that the US is no longer dumping helium, the price has equalized. While it's true that it's mostly non-renewable, the fact is that there's an abundance but it's just not worth recovering. Nearly every natural gas project on the planet just vents the stuff to the atmosphere in truly monumental scales.Quote:
Originally Posted by hemmjo
Also you're totally right about it escaping the atmosphere, and it's super interesting. Helium is monoatomic and very light. To have the similar kinetic energy as other atmospheric gases (i.e. temperature) the atoms have to go super fast. How fast you say? Faster than the escape velocity of the earth. That's why there's no helium in the atmosphere. It shoots off into space and never comes back because it's actually going fast enough to escape the gravity well of the Earth.