A new way to cool magnets to the extremely low temperatures needed for MRI machines may hold the answer to overcoming the effects of the increasing global helium shortage.
Well-known for its use in party balloons, helium is also used in the cooling of superconducting magnets, with the main commercial application being in MRI (magnetic resonant imaging) scanners and particle accelerators. Typical MRI machines use approximately 1,700 liters of liquid helium for cooling purposes, which needs to be periodically replenished. Helium is also employed in semiconductor manufacturing, industrial leak detection and to make breathing easier for deep sea divers and newborn babies.
However, helium is running out, says Dr. Peter Wothers, a fellow of the Royal Society of Chemistry and a University of Cambridge chemist. In a presentation during the Royal Institution’s 2012 Christmas lectures, Wothers explained that helium is becoming increasingly scarce on Earth because of its lightness, which allows it to escape Earth’s gravity into space. Helium conservationists have also argued that extensive frivolous use of the precious gas in balloons has contributed to the present problem.
Also contributing to the shortage is the fact that helium cannot be artificially synthesized and instead is extracted from beneath the Earth’s crust. Approximately 75 percent of the world’s helium supply is produced by the U.S.; in a move to avoid a potential global helium shortage, lawmakers voted earlier this week to prevent the shutdown of a 90-year-old helium reservoir in Texas.
Now, a company called Cryogenic has developed a technique to cool magnets that requires only a small fixed amount of helium—approximately half a liquid liter—and mechanical coolers which run using electrical power and cooling water, Wired said in a recently published article.
According to the technology news outlet, the new system works similar to how an air conditioning unit would function: the coolers rely on the compression and expansion of a fixed volume of helium gas under pressure in a closed, self-contained circuit. Because the helium gas remains cold and does not condense into a liquid, the system avoids the possibility of quenching. While relatively rare in MRI machines, quenching—in which a malfunction causes the helium to convert back to gas and escape the cryogenic chamber, effectively demagnetizing the MRI magnet—can be both damaging to the machine and dangerous to anyone near the machine.
Cryogenic primarily focuses on MRI machines and other instruments used in research facilities, but the development of cooling systems for full body MRI scanners in hospitals is not out of the question, Jeremy Good, managing director of Cryogenic, said.
“In recent years, major research laboratories have had to temporarily shut down multimillion-pound facilities because of these shortages and the problem will only get worse,” he told Wired. “Providing an alternative which doesn’t rely on a regular supply of helium is essential to addressing this problem.”