The Cold Head: Your MRI’s heart and soul, it is crucial to the performance of your machine. But how do you know when it’s time to replace it?
Here’s a quick rundown of what a cold head actually does: the cooling system inside your MRI holds hundreds of liters of liquid helium that are there to keep the enormous magnet inside the MRI cool. The helium turns to gas once it takes on ambient heat. The cold head is the part inside the cooling system that re-condenses the helium gas in order to prevent it from boiling off completely.
The “re-condensing margin” is how you’re able to tell if your cold head is running properly. Because of the enormous amount of cooling the MRI cold head does, it loses about 10% of its cooling power each year, reducing this margin. Listed inside your machine’s OEM documentation is the healthy range of the re-condensing margin. Inside the system’s console is where you can check the metrics of this number.
Red Flags To Look Out For
- Oil or other impurities can get inside your MRI compressor, causing cold head damage, though the issues won’t likely show up for a while. An experienced service provider can help determine your situation by testing the oil and air if you suspect impurities to be present. A little preventative maintenance can help with this as well, because replacing your system’s absorber yearly (the absorber filters oil out, allowing pure helium through) can greatly reduce your chances of oil moving from the compressor to the cold head, causing contamination. If you don’t replace the absorber annually, it’s more likely to reach saturation, and therefore become contaminated.
- Does the re-condensing margin fluctuate or fall while the compressor is working? This is a big warning sign that’s important to pay attention to. Since overall helium levels may not drop at first, many wrongly assume everything is okay with the cold head. But once the helium margin drops to zero, you’re in big trouble. The helium will then begin burning off at an exponential rate, exposing the MRI magnet to an uncooled environment. When the magnet inside the MRI isn’t cooled properly, it will affect image quality and homogeneity of the magnet. With helium burning off at such a rate, this will also increase your chances for quench, which is a sudden loss in superconductivity, and not to mention extremely costly, time draining, and dangerous.
- The lifespan of a cold head varies, but for the most part, if you’ve purchased a refurbished MRI, expect to replace your cold head in 3-4 years. If your MRI is brand new, expect 4-5 years.
- Another red flag to look out for is banging or strange noise coming from the cold head, which could signal a mechanical problem.
Avoid quench by paying attention to your cold heads re-condensing margin, listening for odd noises, and keeping track of its age. If the re-condensing margin does happen to near zero, don’t hesitate in replacing the cold head! Do it as soon as possible, within the week if you can.
Amber Diagnostics’ helpful team of imaging experts are here to answer any questions you might still have about cold head replacement & MRI service. Contact us to get started!