A CT scan technique called parametric response mapping could allow physicians to better distinguish early-stage damage to the small airways of the lungs from more severe conditions, such as emphysema.
"Essentially, with the PRM technique, we've been able to tell sub-types of COPD apart, distinguishing functional small airway disease from emphysema and normal lung function," senior author Brian Ross, Ph.D., the Roger A. Berg Research Professor of radiology, professor of biological chemistry at the University of Michigan Medical School, said in an announcement. "We believe this offers a new path to more precise diagnosis and treatment planning, and a useful tool for precisely assessing the impact of new medications and other treatments."
With PRM, researchers use a computer program to overlay CT lung scans taken during full inhalation with those taken during a full exhalation so that the tissue in the inflated and deflated lungs align. Since the density of a healthy lung will change more between the two images than a diseased lung, researchers are able to construct a 3-D map of the lung, with different areas of the lung color-coded according to the health of the tissue, or the degree of small airway damage.
The authors reported that the technique allowed them to distinguish between early small airway disease and emphysema, and that the degree of COPD as measured by PRM closely matched the patients' performance on standard lung tests.
"In the last decade, CT scan techniques for imaging COPD have improved steadily, but PRM is the missing link--giving us a robust way to see small airway disease and personalize treatment," study co-author Ella Kazerooni, M.D., M.S., FACS, a radiology professor who leads U-M's lung imaging program and is a member of the COPDGene trial, said.