MRI Quenching - What it is, Why It Happens, and How to Prevent It

MRI Quenching 101 and How You Can Avoid It

As safe as MRI systems are considered to be (especially since, unlike other types of diagnostic imaging equipment, MRIs do not produce radiation), there are certain incidents that you should be aware of. For example, quenches. A quench will cause the entire MRI to shut down. Generally speaking, try to avoid quenching because it could cause damage to your MRI system and often results in significant downtime. If proper safety protocols aren't followed, a quench could, in rare instances, present a safety risk as well.

What is MRI Quenching?

MRI systems use superconducting magnets to produce powerful magnetic fields. To remain superconductive, the magnet coils must remain near zero degrees. It's why they are bathed in liquid helium, which reaches temperatures of -452.2 degrees Fahrenheit. If the temperature of the coil goes above the threshold, then a finite resistance will develop in the coils windings. The current passing through this increased coil resistance creates heat, which, in turn, causes the liquid helium to suddenly boil off. When this happens, the magnetic field is lost.

The helium, which is turned into gas during a quench, is released. A properly set up MRI room will contain emergency venting systems to safely remove the helium gas from the room.

How Does MRI Quenching Happen?

There are two types of MRI quenches. The first occurs as a result of a disruption or problem with the MRI's magnet system. The second is a deliberate quench in which the emergency Magnet Stop button is pressed and a quench is activated.

1. The Magnet Stop button should only be activated in the event of an emergency. For example, if a fire breaks out in the MRI room, a quench should be activated. Additionally, a quench should be executed if the patient's life is in danger. For example, if a ferrous metal was brought into the MRI room without the knowledge of the MRI staff and it was activated by the magnet, turning it into a dangerous projectile that has pinned someone down or injured someone. A planned quench will also be executed if the MRI system is being decommissioned.

2. There are several reasons why an MRI might quench on its own. Any failure of the MRI cooling system - chiller, compressor, cold head or lines - could cause excess helium loss which, if uncorrected, will eventually cause a quench when the helium gets too low. This is why it's important to have helium levels monitored consistently. In any case, if your MRI quenched on its own, it was due to the failure of something, which is why you'll need to have the system carefully inspected to diagnose the problem.

Is MRI Quenching Dangerous?

If a quench occurs, whether planned or unplanned, the room will need to be cleared right away. The first danger it presents is when the quench actually occurs. The execution of a quench results in an incredibly loud bang, which can rupture your eardrums if you're too close. There are also some potentially life-threatening risks to a quench as well.

Helium gas will be expelled from the machine at a rapid pace. Helium gas can be very dangerous. It's why MRI rooms are built with emergency ventilation systems. If the ventilation system fails, helium will begin building up near the ceiling (helium is lighter than air) and work it's way down. Although it is non-toxic and non-flammable, it will displace the oxygen in the room and cause asphyxiation if anyone is still present. Because helium gas is so cold, exposure can also lead to hypothermia.

On top of all of that, the released helium will cause the pressure inside of the room to build up. If the room isn't evacuated right away, the increasing pressure could make it difficult to open the door leading out of the room. If this happens, the window between the examination room and the control room will need to be shattered. Shattering the window needs to be done carefully since the built-up pressure in the room could send the glass flying, causing potential injury to anyone inside. Fortunately, most modern MRI rooms are designed to allow the door to be easily opened despite changes in room pressure.

As long as the room is properly ventilated and proper safety procedures are executed when a quench occurs, nobody should be in danger. Usually, the biggest risk is that of damaging the MRI's magnet.

How to Prevent MRI Quenching and It’s Dangerous Effects

Not only can unplanned quenching be dangerous, it can be incredibly expensive. The MRI can sustain serious damage during a quench, resulting in lengthy downtime and expensive repairs. Then the MRI will need to have its helium levels refilled since a substantial amount of helium will have been boiled off and expelled. Liquid helium, of course, does not come cheap.

The best way to avoid quenches is to regularly maintain your MRI system and follow all safety precautions carefully. For example, always make sure to interview anyone that goes into the MRI room to make sure they do not have ferrous metals implanted in their bodies. They should also change into MRI room-appropriate clothing (there are certain types of clothes that are manufactured using metal elements).

Preventative maintenance is another important step in preventing quenching. During routine maintenance, a thorough inspection will be done to ensure that all of the MRI's components are working properly. Components that are damaged could fail, causing a quench. Even if you take every precaution possible, make sure your staff knows exactly what to do in the event of a quench. This will help to ensure that everyone is safely evacuated and that the proper emergency response is executed.

Working With an MRI System Takes a Lot of Knowledge and Training

MRI systems are complicated machines. A quench, whether planned or unplanned, can not only cause expensive damage, it could be a potential safety risk to anyone in the MRI room. As a result, it's vital that only highly-trained personnel be allowed near your MRI system. It's also incredibly important that you maintain your MRI. Considering how much an MRI machine costs to begin with,  skipping routine preventative maintenance is simply not an option.