“If you want to image the void spaces in the lungs, you need some sort of a signal source there,” Singh says. “Magnetized xenon or helium could be that source.”
In a normal MRI, say on a knee or shoulder, the water in the body is used as the signal source. But in the lung there is very little water. Something else is needed to take its place.
“The gases are very useful for understanding lung diseases in which defects in the lungs prevent air from passing through certain parts of the lungs or prevent oxygen from entering the bloodstream,” Singh explains.
Paper Clip Magnets
The problem, he says, is that these gases in their natural state are unmagnetized which prevents them from creating these images. In order to magnetize the gases, they are mixed with a tiny amount of impurity atoms and exposed to laser light.
The laser light magnetizes the impurity atoms, which subsequently magnetize the gas atoms through atomic collisions. Singh compares it to taking a paper clip, rubbing it against a magnet, resulting in the clips becoming magnets themselves.
Currently, those two gases are used only for research and development purposes in radiology departments.
“We hope,” Singh says, “to sometime soon make the transition from an R&D tool to a diagnostic tool.”
Of the two, xenon would be the gas of choice. It is naturally occurring, thus less expensive, and is more easily absorbed into the bloodstream, which offers potential uses for other MRI imaging of the body, particularly the brain.
“Unfortunately,” Singh says, “it is much easier to magnetize helium than xenon.”