por Brendon Nafziger
, DOTmed News Associate Editor | May 17, 2012
But another, longer term answer might be switching the materials used in the magnets themselves.
Nearly all MRI magnets use niobium-titanium wires, which are superconducting only at the extremely cold temperature of 9.5 kelvins, equivalent to about -443 degrees Fahrenheit. (For comparison, Pluto's surface temperature averages about 44 kelvins.) Helium boils at 4.2 kelvins, so it's the only refrigerant that can be used to operate niobium-titanium-based magnets, Jarvis said.
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However, GE is investigating alternatives. Two years ago, the company was the recipient of a $3.27 million National Institutes of Health grant to look into using magnesium-diboride wires. Although this alloy is costlier than niobium-titanium right now, its "critical temperature," or the point at which it becomes superconducting, is much higher, at 39 kelvins (a temperature it would reach on the surface of Pluto, incidentally, during the dwarf planet's coldest periods, at 33 kelvins).
"In future there are other superconductors that hold promise that we're continuing to do work with, that could be cooled using other refrigerants or directly without use of refrigerants," Jarvis said. "We're looking at a variety of projects and programs."
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