TUESDAY, May 30, 2006 (HealthDay News) -- A new MRI technique spotted emphysema early in smokers who otherwise showed no symptoms, U.S. researchers report.
The MRI procedure identified signs of the disease that CT scans, the current primary test for emphysema, didn't. And, unlike CT, it also spared patients exposure to radiation.
"With this technology, we have shown that it is possible to measure the severity of emphysema and its progression through time without the radiation exposure of lung CT tests," said study author Sean B. Fain, an assistant professor of medical physics and radiology at the University of Wisconsin, Madison.
In the study, which was supported by the National Institutes of Health, 19 volunteers inhaled "hyperpolarized" helium, and then had their lungs screened with two different MRI tests. The first test showed areas of the lungs where oxygen could not pass. The second test, called an "apparent diffusion coefficient" (ADC) map, showed the size of the air sacs in the lungs. Since emphysema causes air sacs to grow, the ADC map indicates the stage and location of the disease.
"The ADC maps are very sensitive to changes in the lung structure," Fain said. "With this tool, it was shown that even smokers that appear healthy have enlarged lung airspaces that suggest emphysema is already developing."
Eleven of the volunteers smoked, but had no symptoms of emphysema. The other eight volunteers did not smoke. The more the volunteers had smoked, the more damage to the lungs the map showed. Damage was far worse in smokers with more than 18 pack years, or the equivalent of one pack of cigarettes per day for 18 years, than in nonsmokers.
"On average, smoking accelerates emphysema-like changes at about twice the normal rate found with aging," Dr. Fain explained.
The study appears in the June issue of Radiology.
Researchers also conducted CT scans on the same volunteers after the MRI, but the CT did not pick up the damage found by the MRI. The MRI and hyperpolarized helium technique was two and a half times more accurate than the CT, and 10 times more accurate than standard MRI.
Emphysema is a chronic lung disease that affects more than 3 million people in the United States, and millions more may have the disease but have not yet been diagnosed.
For more on emphysema, head to the American Lung Association.