Breathe (xenon) deeply to see lungs clearly.

Someday, a whiff of the inert gas and general anesthetic xenon may help reveal the inner workings of the lungs and the brain. Researchers seeking to study these organs have figured out how to use xenon to enhance the ability of magnetic resonance imaging (MRI) to visualize tissues.

Typically, MRI depends on the protons in a tissue's water molecules, which give off a signal when subjected to a graded magnetic field. That signal helps the MRI's machine generate a picture.

The technique doesn't work well in places with relatively little water, however, such as cell membranes or the fatlike sections of the brain, says Mitchell S. Albert of the State University of New York at Stony Brook. Also, the lungs' air sacs create a mosaic of gas-liquid boundaries that make MRI difficult, if not impossible, with water protons, says Arnold Wishnia, a biophysical chemist at Stony Brook.

Because xenon doesn't build to very high concentrations in tissues, the team had to learn how to boost the magnetically induced signal from the gas. In addition, MRI's magnets cause only some xenon protons to change their spin state. About an equal number of protons do not change. As a result, the difference between the total number in each state is small, and the resulting signal is weak.

If the researchers first pummel xenon atoms with excited rubidium atoms, they can generate a much stronger signal, Albert, Wishnia, and their colleagues report in the July 21 NATURE.

They excite the rubidium with a laser, then add it to xenon, Albert explains. They can keep the resulting hyperpolarized xenon in this altered state for several hours by keeping it chilled and in a magnetic field. "The enhancement you get is between 10,000 and 100,000 times [normal]," Wishnia says. As a result, images of lungs have incredibly high resolution, even when produced using commercially available MRI machines.

Another technique, high-resolution X-ray computerized tomography, can detect lung damage, but it requires radiation and much more time than the modified MRI, Wishnia says. Once inhaled, xenon loses its polarization within about 35 seconds. Yet because it takes just 0.6 second to "snap" an MRI picture, plenty of time exists for multiple shots, he adds.

"For [imaging] the lung, xenon will absolutely be the method of choice," Wishnia predicts.