CT Scan that Measures Blood Flow could Be New Test for Identifying Smokers at Risk for Emphysema

Researchers at the University of Iowa, led by Eric Hoffman, PhD, professor of radiology, internal medicine, and biomedical engineering, have determined that CT scans that measure blood flow in the lungs may be an effective tool for identifying smokers at risk for emphysema.

The researchers used multi-detector row CT imaging to measure blood flow in the lungs of 41 patients—24 who smoked and 17 who did not. Although all patients had normal lung function, half of the smokers showed very subtle signs of emphysema. In addition, these 12 patients had the most disrupted patterns of blood flow.

According to Hoffman, the study findings support the hypothesis that abnormal blood flow can occur even before emphysema develops.

"Although the underlying causes of emphysema are not well understood, smoking increases the risk of developing the disease," Hoffman said. "Our study suggests that some smokers have an abnormal response to inflammation in their lungs; instead of sending more blood to the inflamed areas to help repair the damage, blood flow is turned off and the inflamed areas deteriorate."

Writing in the April 5 early online edition of Proceedings of the National Academy of Sciences, the researchers said, “assuming that all smokers have a consistent inflammatory response, increased perfusion heterogeneity in emphysema-susceptible smokers would be consistent with the notion that these subjects may have the inability to block hypoxic vasoconstriction in patchy, small regions of inflammation.”

The authors conclude that their findings “demonstrate a functional lung-imaging measure that provides a more mechanistically oriented phenotype that differentiates smokers with and without evidence of emphysema susceptibility.” The findings also suggest that “the ability to distinguish when to turn off or when to ramp up blood flow is defective in some people,” which may be due to genetic differences, according to the researchers. If this eventually is proven to be true, the researchers note that this genetic difference, coupled with smoking, would increase one’s risk for emphysema.