by Brendon Nafziger
, DOTmed News Associate Editor | May 17, 2012
In addition to the 5 million liters used in production, roughly 6 million liters are also used in maintenance of devices already in hospitals and clinics.
Jarvis said newly installed magnets need to be "topped up" with a couple of hundred liters of helium that are lost during transit (the longer the transportation, the more helium is evaporated). However, thanks to technology developed over 15 years ago, modern magnets generally don't need routine helium infusions, Jarvis said.
Routine helium infusions are unneeded because in the late 1990s, GE introduced so-called zero boil-off technology to its MRIs, Jarvis said. In this, helium that evaporates from heat in the magnet is recondensed and returned to the system.
"It stays as a closed cycle system. No helium is required to be added," Jarvis said.
By 2004, GE was selling exclusively zero boil-off technology MRIs, Jarvis said. However, even these "zero boil-off" magnets might need occasional small amounts of helium when the coldhead compressors, used to recondense the gas, are serviced every couple years. They can also need substantially more helium if a power outage causes the cooling systems to crash, resulting in larger boil-offs. This is a danger that besets magnets in countries with less reliable electricity delivery services, Jarvis said.
Also, not all MRIs in operation today were built post-2004. Many "legacy" machines are still working, either in their original place of installation or having been resold to a new buyer, often in another country. Jarvis estimates maybe 20 percent of systems are running with the pre-zero-boil-off technology.
"Old magnets simply never die," he jokes.
In his testimony, Rauch said GE has invested about $1 million in technology in its factory to bolster helium recycling and conservation. One investment was in recapturing equipment, used to snag helium lost in the manufacturing process, which is then recompressed and sold back to the gas suppliers at the factory.
Jarvis said the company's also working on proprietary efficiency-boosting techniques. For instance, workers might pre-cool a magnet with liquid nitrogen, which is cheaper and easier to get, before filling it with helium. He said they have also been running computer dynamic fluid simulations to study how liquid helium is transferred and used, and have committed some engineering know-how to improving the transfer lines from the tankers to the magnet.
"The transfer lines can be heavily optimized, in terms of material construction, control systems, to best match them to the end vehicle, the magnet that's receiving the helium," he said.