A team of researchers from the University of Michigan Medical School, Ann Arbor, has used a technique called parametric response mapping (PRM) to analyze scans of the lungs of patients with chronic obstructive pulmonary disease, known as COPD. By analyzing the computed tomography (CT) scans of COPD patients they found that the PRM technique permitted them to better distinguish between early-stage damage to the small airways of the lungs, and more severe damage called emphysema.

Originally developed to show the response of brain tumors to treatment, the PRM technique enables the identification of COPD-specific changes in three-dimensional lung regions over time. Using PRM, the researchers overlaid the CT scan taken during a full inhalation with an image taken during a full exhalation. The images share the same geometric space, so that the lung tissue in the inflated and deflated lungs aligns. They saw that the density of healthy lung tissue changed more between the two images than did the density of diseased lungs. This allowed them to create a three-dimensional "map" of the patient's lungs.

PRM assign colors to each small 3-D area according to the difference in signal changes within each of the areas between the two scans. Green means healthy, yellow means a reduced ability to push air out of the small sacs, and red means severely reduced ability.

This could help physicians personalize therapy for individual COPD patients, and to be able to select patients for clinical trials more easily, based upon the severity of their disease progression.

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