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MRI Technique Detects Early Emphysema

Posted on: Tuesday, 30 May 2006, 18:00 CDT

By CHRISTINE DELL'AMORE

A novel imaging technology that detects transformations in the lung may warn of impending emphysema in smokers more effectively than current methods, a new study shows.

Researchers were able to find degraded lung function in patients by measuring the diffusion of helium gas into the lung's air sacs, or alveoli, where the exchange of oxygen and carbon dioxide takes place. The current gold standard for emphysema screening is CT scans.

This actually detected structural change in asymptomatic volunteers. That's what's exciting -- the technique is sensitive enough to detect early onset of change, said lead author Sean B. Fain, professor of medical physics and radiology at the University of Wisconsin, Madison.

The study will be published in the June issue of the journal Radiology.

Fain and colleagues recruited 19 adult volunteers -- 11 smokers and eight non-smokers -- to participate in the study. The subjects inhaled a type of benign helium gas that is insoluble in the blood. The researchers then performed MRI tests of the lungs to see how the helium expanded into the air sacs. With this detailed approach, scientists can measure the structure of the lungs at 100 to 500 microns in size -- a superior resolution to the CT scan.

The researchers further confirmed the scans by producing a map of the lungs, called an ADC map, that shows the size of the air sacs.

Emphysema is a chronic lung disease that affects more than 3 million Americans, most of them smokers, according to the ALA. As the disease progresses, the air sacs break down and elasticity of the lung tissue is lost, impairing the exchange of oxygen and carbon dioxide. The walls between air sacs also disintegrate, creating large spaces.

For example, Fain found a smoker of 18 years had major abnormalities in the structure of his alveoli, suggesting early onset of the disease, Fain said.

A follow-up study authored by Fain, published in 2005, also used the MRI and helium technology to test a range of volunteers from 18 to 64. He found similar lung deterioration takes place in non-smokers as they age -- suggesting that everyone may experience a low-level degradation in their lungs over time. People who smoke or have a genetic predisposition could face accelerated loss of lung function.

So should lifelong smokers scramble to take these helium-based MRIs? Not necessarily, as the technology is too expensive and cumbersome for mass screening.

But smokers should regularly visit their doctors to check for chronic obstructive pulmonary disease, or COPD, which comprises chronic bronchitis and emphysema, said Norman Edelman, chief medical officer for the American Lung Association.

Most smokers don't get tested, he said, partly because the symptoms of emphysema -- shortness of breath, coughing and inability to exercise -- are easily brushed off as normal aging.

Once diagnosed, emphysema can be treated, although existing medications focus on alleviating symptoms rather than addressing the destruction of the lung.

However, this new MRI technology could be vital in helping along drug development for emphysema, said John Mugler, professor of radiology and biomedical engineering at the University of Virginia.

The helium procedure is not as dangerous as CT scanning, in which people accrue radiation, so it can be repeated again and again. This safe method could help researchers determine whether drugs under development really work in halting the progression of emphysema.

Researchers can also apply the technology to investigating other lung diseases, such as asthma and cystic fibrosis, Fain said.

We don't really have good tools to understand progression and underlying mechanisms of these diseases. This provides us a tool that doesn't expose people to ionizing radiation and allows us to study the dynamics of the lungs, he said.

Source: United Press International

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