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What is cold head and why is it important to the MRI

cold head

Anyone who services and works around MRI’s is used to hearing a chirping sound day after day. That sound is your MRI working 24 hours a day 7 days a week. Have you ever stopped to think about what the significance of it is?

The magnetic field of the MRI is created by energizing a super conductive coil inside of the magnet. In order to get the coil superconductive, the magnet is cooled down to -450F using liquid helium. Depending on the type of MRI there can be up to 2000 liters of liquid helium inside the magnet. The liquid helium is constantly boiling due to the heat created by the magnet. In order to eliminate the helium from boiling away the heat that is causing it to boil needs to be removed. The cold head removes the heat from the magnet that causes the helium to boil allowing helium to stay in liquid form and keep the magnetic field intact.

When the cold head is not properly maintained and/or kept running the liquid helium will start to boil inside the magnet. This helium, now in vapor form, is then vented off the magnet through the helium ventilation system and decreases the amount of liquid helium in the magnet. If the liquid helium boils off to a low level it can cause the magnet to quench resulting in additional loss of helium ($15 to $20 per liter), a loss the magnetic field, and could cause other damage.

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