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US cops get gun stuck to MRI machine in bungled cannabis raid
(www.yahoo.com)
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this post was submitted on 29 Sep 2024
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Radiologist here. There are multiple safety zones (four to be precise) around the machine and extensive screening procedures are required to access the inner zones. The magnet of an MRI is always on and extremely strong. However, you need to be pretty close for it to pull a gun from your hands. Like, less than a few meters. That would be zone 4. He should never have been that close.
The button he pressed is called a quench. It's for life threatening emergencies only. Think "patient trapped between the machine and a metal object." It vents the liquid helium used to keep it superconductive and basically destroys the machine, but the magnetic field dissipates in minutes. There is a way to wind the machine down without destroying it in situations that aren't life threatening or for servicing, but it takes hours for the magnetic field to dissipate and even longer to bring it back.
While I knew these machines are really dangerous to bring metals to anywhere near it; it's quite interesting to know that there is a fail safe for these cases.
That's not what a fail-safe is. A fail-safe is just what it says: the device fails into a safe configuration. In this case, someone has to press a button to quench the magnet, which is not really a failure mode of the machine.
A typical fail-safe is something like a solenoid valve. The valve has a default position when no power is given to the solenoid, and you should design your machine so that the default position is safe (whether that be open or closed). The most likely failure mode is a power loss, so the configuration is said to be fail-safe.