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How Is Liquid Helium Used in MRI Scanners?
Let’s explore how liquid helium is used in an MRI device. An MRI scanner consists of current-carrying coils, a magnet, and connecting wires. For MRI scanners to operate effectively, the magnetic coils must be given superconducting properties—this requires a powerful coolant. Liquid helium serves this purpose by enabling electric current to pass through the coils with minimal resistance, allowing the generation of strong and stable magnetic fields.
Why Is Liquid Helium Important in MRI Machines?
Liquid helium is an ideal element capable of reaching the extremely low temperatures required for superconductivity in MRI scanners. It cools the superconducting magnets—responsible for producing detailed images of the human body—down to below 4.15 Kelvin (-269°C). Thanks to helium, MRI systems can operate effectively and reliably.
Curious About What Superconductivity Is?
It is a physical phenomenon that occurs in certain materials when exposed to extremely low temperatures. It allows electric current to pass through a conductor without any electrical resistance—resulting in zero energy loss.
What Should You Consider When Refilling Helium in MRI Machines?
MRI magnets can have varying helium capacities—up to 1800 liters. Refill the MRI machine before the helium level drops below 40%. Before deciding where to purchase helium, be sure to check its availability, pricing, and logistics. Keep in mind that helium prices can vary by country and fluctuate based on current supply and demand conditions. Maintain the cryocooler in good condition, and have a dedicated service plan in place—different MRI scanners may require different types of maintenance. Following these tips will not only extend the time between helium refills and save you money, but also help prolong the lifespan of your MRI system.
What Should You Know About Cryocoolers, Also Known as Cold Heads?
Cryocoolers reduce boil-off rates and help condense helium from its gaseous form back into a liquid state. There are two main types: Pulse Tube (PT) and Gifford-McMahon (GM) cryocoolers.
What Are the Key Differences Between Pulse Tube and Gifford-McMahon Cryocoolers?
In general, GM cryocoolers are less expensive than PT cryocoolers offering comparable cooling performance. Both are mechanical coolers that produce a certain level of vibration, which can affect the functionality and lifespan of the cryocooler. However, the vibration level at room temperature is significantly lower in PT systems compared to GM systems. Another key difference lies in their orientation requirements. PT cryocoolers operate properly only when positioned completely vertically, whereas GM cryocoolers can function in any orientation.