Non-invasive imaging for small airway lung disease

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the US, with approximately 16 million Americans currently affected. 

Researchers at the University of Michigan have reported on the ability of Parametric Response Mapping (PRM), a relatively new technique, to identify small airway abnormality in COPD.

Currently, it is difficult to identify abnormalities in small airways non-invasively, as the tiny bronchioles that are initially damaged are around two millimetres in internal diameter, and as such are too small to be imaged using computed tomography. 

PRM was developed at Michigan Medicine, in a study led by Dr Brian Ross, Professor of Radiology and Biological Chemistry, and Dr Craig Galban, Associate Professor of Radiology. The technique measures lung density during inhalation and exhalation. 

Using lung tissue from patients undergoing transplantation, and donated healthy lung tissue, researchers mapped the samples back to CT scans taken before surgery. The team was able to non-invasively identify small airway loss, narrowing and obstruction.

Senior author Dr MeiLan Han, a lung specialist and Professor of Internal Medicine at the University of Michigan, said, “Now we have confidence in our ability to identify airway disease when imaging COPD patients. PRM is already clinically available and used by University of Michigan clinical teams to assess patients with COPD. This is what we mean by bench to bedside medicine.”

The study was conducted in patients with a severe form of the disease. A NHLBI funded study, COPDGene, found that the PRM-defined small airway abnormalities have been detected on CT scans of patients with milder disease and could help to predict patients who will lose lung function.

Prof Han said, “We still need to validate the type of airway disease the PRM technique identifies in patients with milder disease. That type of lung tissue is more difficult to obtain, but we are working on techniques that would allow us to use smaller amounts of lung tissue to make such studies feasible.” 

The study was published in the American Journal of Respiratory and Critical Care Medicine.