November 1, 2013 Volume 77, Number 11
ACE Question

Which statement about the occurrence of a quench (magnet releasing its stored energy as heat) in the magnetic resonance imaging (MRI) scanner is MOST likely true?


 (A) It most commonly occurs when a life-threatening emergency requires shutdown of the magnet.

 (B) Oxygen administration to the patient should be discontinued.

 (C) All personnel should move into zone IV (scanner room).

 (D) Precautions against the hazards of a magnetic field no longer need to be taken.


One of the emergency situations unique to the magnetic resonance imaging (MRI) suite is the development of a quench and the possibility of a catastrophic outcome. A quench results when the magnet turns resistive, and all of its stored energy is released. The heat produced by this process results in the vaporization of coolant (stored cryogens). This was one of the issues addressed in the recently published American Society of Anesthesiologists Practice Advisory on Anesthetic Care for Magnetic Resonance Imaging since anesthesiologists should know how to respond appropriately if this emergency occurs while caring for a patient.


A quench most commonly occurs when a life-threatening emergency requires shutdown of the magnet, such as the presence of an accidental projectile. It may also occur when a technician inadvertently shuts down the magnet. An uncontrolled quench may result in loss of oxygen from the scanner room if adequate venting of the released gases does not occur. Therefore, the patient and any personnel present in the scanner room (zone IV) should immediately be moved out of this zone, and oxygen should be administered immediately to the patient to prevent hypoxia. However, development of high pressure within zone IV caused by the release of gases during the quench can make it impossible to open the door and gain access to the scanner room, leading to disastrous consequences.


Although a quench usually results from a shutdown of the magnet, magnetic fields may still be present after a quench. Therefore, the precautions normally followed in the MRI suite still need to be followed. Since this emergency situation may lead to the arrival of emergency response personnel, it is important that these responders be made aware of MRI precautions.


Answer: A


Anesthesiology Continuing Education (ACE) is a self-study CME program that covers established medical knowledge in the field of anesthesiology. ACE can help fulfill the CME requirements of MOCA®. To learn more and to subscribe, visit



  • Stensrud PE. Anesthesia at remote locations. In: Miller RD, ed.s. Miller’s Anesthesia, 6th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2005:2645–2646.
  • American Society of Anesthesiologists Task Force on Anesthetic Care for Magnetic Resonance Imaging. Practice advisory on anesthetic care for magnetic resonance imaging. Anesthesiology. 2009;110(3):459–479.