Measures are put in place to ensure the safety of patients and staff in the event of a quench
Risks associated with magnet quench
- A quench is an event that occurs when a superconducting magnet (such as those used in MRI) loses its superconductivity and undergoes a rapid increase in the resistivity of the magnet coil1.
- The quench process once set off cannot be reversed and takes approximately two minutes2
- The quench generates heat that results in the rapid evaporation, or boil-off, of the magnet coolant (liquid helium)1
- There are two situations in which a quench may occur1:
- Spontaneously: due to some force or disruption to the magnet system (these events are rare)
- Intentionally: when the “Magnet Stop” button is depressed in response to an emergency situation
- Evaporated helium created by a quench poses an immediate hazard to those in the vicinity of the magnet and the quench exhaust vent:
- The coolant is extremely cold and can cause cold burn and frostbite within seconds for those that come into contact with it
- The rapidly released gas can enter the MRI scanning room (if there is a problem with the venting) and displace the oxygen, posing a risk for asphyxiation
- A quench can also cause damage to the MRI equipment and disruption to the function of a department:
- A quench can potentially damage the MRI magnet itself
- Regardless of the damage done, a quench will result in at least several days of system down-time, and recovery to operation is expensive
- Intentional quench is an emergency measure to be initiated in cases where no other alternative will suffice1:
- Fire that cannot be controlled by the non-magnetic fire extinguisher
- An individual pinned against the magnet, trapped or in a potentially life-threatening situation by a non-removable ferrous object
- In case of an intentional quench:
- The MRI department is evacuated
- The exhaust fan is activated
- The door to the scan room is fixed open – a build-up of pressure in the scan room could make an inward opening door difficult to open3
- Following the quench, the MRI department should remain evacuated until a suitably qualified person (e.g., a representative of the supplier) has inspected the system and confirmed it is safe.
Precautions for a quench emergency
- MRTs should be aware of any and all local or provincial guidelines that relate to quench in their facility.
- An accidental quench requires immediate evacuation of the vicinity.
- Procedures are put in place to establish evacuation routes and responsibilities
- Evacuation procedures are reviewed by all staff on a regular basis
- Safety measures are implemented to allow exit from the scan room in case of a quench emergency. These may include:
- A reconfiguration of the door so it opens outwards
- Installation of sliding doors that can be opened in an emergency
- Installation of emergency escape/ventilation panels on the door or in a suitable wall
- Provision of emergency equipment to allow MRTs to break a window in the event of door malfunction
- Police and fire response personnel are restricted from entering the MR scan room with their equipment until it can be confirmed that the magnetic field has been successfully dissipated4.
Queen’s University. Centre for Neuroscience Studies. Standard Operating Procedures: Emergency Shutdown and Quench Procedures. Available from: http://neuroscience.queensu.ca/MRI-facility/operation-procedures/shutdown. [Accessed 28 May 2018]
Louisiana State University Health Shreveport Radiology Department. MRI Quenching the magnet. Available at: http://www.sh.lsuhsc.edu/raddept/pdf/sec14/Rad%20Proc%2014.13.pdf. [Accessed 3 Nov 2014]
Medicines and Healthcare products Regulatory Agency (MHRA). Device Bulletin: Safety Guidelines for Magnetic Resonance Imaging Equipment in Clinical Use. Available at: http://www.mhra.gov.uk/home/groups/dts-iac/documents/publication/con2033065.pdf. [Accessed 3 Nov 2014]
Kanal E, Barkovich J, Bell C, et al. ACR Guidance Document on MR Safe Practices: 2013. J Magn Reson Imaging 2013;37:501-530.