Helium-based MRI scans may one day allow closer look at smoker lungs

Aided by a powerful imaging technique, scientists have discovered they can detect smoking-related lung damage in healthy smokers who otherwise display none of the telltale signs of tobacco use.

Researchers at the University of Wisconsin-Madison were able to probe deeper into smokers' lungs by tracking the movement in the respiratory organs of a harmless gas known as helium. Helium can be inhaled and visually detected via the widely used diagnostic technique known as magnetic resonance imaging (MRI), which produces high-contrast images of the body's soft tissues. The use of helium is a departure from traditional MRI, which typically distinguishes body tissues from one another by tracking differences in water content.

Writing in the journal Radiology, the UW-Madison scientists suggest that in comparison to existing imaging methods, the helium-based approach could enable doctors to assess lung health more accurately, as well as spot smoking-associated diseases much sooner.

"It's one thing to see a [lung] disease that was already diagnosed, but another to see changes that no one predicted were there," says lead author Sean Fain, a UW-Madison assistant professor of medical physics. "This approach allows us to look at lung micro-structures that are on the scale of less than a millimeter."

Cigarettes can contribute to the onset of respiratory conditions such as emphysema, bronchitis and asthma. In emphysema in particular, the alveoli - tiny sacs in the lungs that transfer oxygen to blood - gradually break down. Fain and his team therefore reasoned that helium gas molecules are likely to have more space to move around in lungs with fewer functioning alveoli.

Testing that theory among eight non-smokers and 11 healthy smokers with no obvious lung damage, Fain found that the movement or "diffusion coefficient" of helium gas molecules did indeed correlate with how much a person smokes, with greater movement indicating a higher level of lung damage. But a more commonly used imaging technique, known as computed tomography, failed to register a similar correlation.

"Our technique is potentially more sensitive than established [imaging] techniques," says Fain. "This is the first time structural changes have been shown in the lungs of asymptomatic smokers."

Fain says helium-based MRI scans could one day help to gauge the efficacy of experimental drug therapies aiming to reduce smoking-related lung damage. The approach may also help to screen for people who might be genetically predisposed to conditions such as emphysema. In future work, Fain plans to dig deeper, to understand the underlying factors that lead to micro-structural breakdown in lungs.

Other co-authors of the study were Michael Evans, an assistant researcher in the department of biostatistics and medical informatics; Thomas Grist and Frank Korosec, both UW-Madison professors of radiology; and Shilpa Panth, a biomedical engineering researcher.