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What Are MRI Cold Heads?

Oct 21, 2020 | Articles, MRI

Helium Dewers

Source: Beckman Institute

MRI imaging equipment is complex in both mechanics and computer technology, but is, very basically, a machine that scans the body using radio waves, and uses electromagnetic field data to create images of different parts of the body. Magnetic Resonance Imaging machines require quite a bit of energy, a specially designed containment area, and climate control in order to work properly and reach their optimal life spans.

The Cold Head of an MRI machine works to keep the machine cool during imaging. MRIs require a lot of energy, as mentioned, to create images, and one of the byproducts of this energy transfer is heat. For this reason, the cooling mechanism of the MRI machine is especially important for preventing the machine from quickly overheating. The cold head is one component of the cooling system.   


What do they do?mri cold head

The MRIs cooling system is a helium-based system that keeps the magnet cool during imagining. The magnet works with a superconductive coil to create an electromagnetic field. In order to keep the magnet cool, it contains liquid helium. The liquid helium is constantly boiling, and will quickly begin to evaporate if exposed to too much heat, so the cold head works to eliminate this excess heat.

The cold head is used to recondense gaseous helium that has evaporated from the liquid helium inside. Once recondensed, it can be added back to the supply of liquid helium. In the event that the machine becomes too hot and too much helium is evaporated from the magnet, it can cause the magnet to quench and begin purging helium, which can be expensive to replenish. If the liquid helium runs too low for too long, it can cause further damage to the machine.  


Why Are Operating Temperatures Important During an MRI?

In order for the magnet and coil of an MRI machine to create a magnetic field strong enough to scan a patient, it needs to be a superconductor. Super conduction requires near zero temperatures, so the magnet is cooled by the liquid helium. Other parts of the machine needed to maintain a cool operating temperature for proper operation as well. Keeping the machine and its parts at ideal temperatures throughout operation will maximize the lifespan of its parts. 

How long do they last?

Speaking of parts’ lifespans, it is important to monitor the condition of your MRI parts, including the cold heads. Cold heads can be purchased new or refurbished, and prices and lifespan can vary widely. On average, new cold heads can last around 4 years and refurbished cold heads can last around 3 years, although extremes for both do exist.

You may realize that the cold heads require replacement when you notice a dropping or fluctuation in recondensing margin, or contamination of your helium. Fluctuation in your recondensing margin can happen even when your compressor is still working, and can lead to greater helium losses (through ventilation) if not investigated early. Greater helium loss can put your machine at risk for a helium margin of zero, which means the magnet is no longer being properly cooled. This could read to further damage to your machine.

Contamination in your helium can begin gradually, but needs to be addressed as soon as possible. Wear on your machine’s filtration system can lead to oil particulates contaminating the system’s helium supply, which can lead to further complications down the road.


How Are They Maintained?

The most effective ways to maintain all of the mechanisms of your MRI machine is to use it in accordance with its operator’s manual. Allowing only trained professionals to operate the machine in a climate controlled environment is also key. But preventative maintenance can also be long to maximize the longevity of some of your commonly replaced parts, including the cold heads.

Replacing your system’s absorber can help prevent oil contamination that can reduce the lifespan of your cold heads. The absorber is the final filtration barrier in preventing oil from contaminating the helium, and just like any filter, needs replacement when saturated. Absorbers should be replaced annually, or whenever needed, whichever is most frequent.

You can also talk to your service provider about contamination testing, in order to be proactive about absorber replacement. Monitoring and understanding fluctuation in your re-condensing margin is also an important way to ensure proper operation of your cold heads. 

When Should They Be Replaced?

Replace your cold heads when you recognize any of the diagnostic symptoms mentioned above. Again, there are options for both new and refurbished cold heads, and each has its own life expectancy and price range, which usually depends on the condition and make/model of MRI scanner you’re using. Typically, cold head replacement for the MRI costs between $5,000 to $10,000. 


How We Can Help

If your helium levels are starting to fall, your cold head might be starting to fail. Catching this early will help avoid costly helium fills, we sell new and refurbished MRI cold heads with extended warranties. Please send us an email or give us a call.

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