Last revised by Andrew Murphy on 02 Apr 2020

Quenching refers to rapid expulsion of the liquid cryogen used to maintain the MRI magnet in a superconducting state.


Modern MRI scanners contain superconducting magnets which have very low energy consumption, made possible by maintaining internal subzero temperatures by way of a 'cryogen bath' of liquid helium. In the event that somebody pushes the emergency stop button or there is an equipment fault, the liquid helium boils off rapidly accompanied by a loud banging or hissing sound, safely expelled from the building by means of a dedicated venting system.


Extremely rare but if for some reason the gas should escape into the room instead of being vented outside the building, there is a risk of asphyxiation and frostbite.

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