New Approach to Scanning to Improve Diagnosis of Lung Diseases

One of the common medical conditions worldwide is lung disease. Millions of people in the U.S. have lung disease. According to the Medline Plus, if all the types of lung diseases are clubbed together, it is the number three killer in the U.S as most of them go undetected.

However, a new approach in lung scanning promises to improve the diagnosis and treatment of lung diseases, in nearly 24 million Americans.

A team of researchers from the University of Michigan Medical School have produced a technique called as parametric response mapping (PRM). The PRM was used to analyze computed tomography, or CT, scans of the lung disease patients with chronic obstructive pulmonary disease (COPD). These patients participated in the national COPD gene study funded by the National Heart, Lung and Blood Institute.

Smoking is the leading cause of COPD. It limits the patients breathing ability causing shortness of breath, coughing, wheezing and reduced ability to exercise, walk and do other things. As their disease worsens the patients get disabled. COPD can also result from long-term exposure to dust, and certain gases and chemicals. There is no cure for COPD

According to the researchers, PRM technique allows them to better distinguish between early-stage damage to the small airways of the lungs, and more severe damage known as emphysema.  Plus the overall severity of a patient's disease, as measured with PRM, matches closely with the patient's performance on standard lung tests based on breathing ability.

"Essentially, with the PRM technique, we've been able to tell sub-types of COPD apart, distinguishing functional small airway disease or fSAD from emphysema and normal lung function," says Brian Ross, Ph.D., the Roger A. Berg Research Professor of radiology, professor of biological chemistry and senior author of the new paper. "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."

"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," said Ella Kazerooni, M.D., M.S., FACS, a radiology professor who leads U-M's lung imaging program and is a member of the COPD Gene trial.

PRM technique that was originally developed to show the response of brain tumors to treatment now allows researchers to identify COPD specific changes in three-dimensional lung regions over time.

Powerful computer techniques are being used along with PRM to overlay the CT scan taken during a full inhalation with an image taken during a full exhalation. The overlaid, or registered, CT images share the same geometric space, so that the lung tissue in the inflated and deflated lungs aligns. The density of healthy lung tissue will change more between the two images than the density of diseased lung, allowing researchers to create a three-dimensional map of the patient's lungs.

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

Till date the best test for COPD is a lung function test called spirometry which involves blowing out as hard as possible into a small machine that tests lung capacity. The results can be checked right away, and the test does not involve exercising, drawing blood, or exposure to radiation.

"By distinguishing small airway abnormality from that involving the lung parenchyma, such as emphysema, PRM could help physicians personalize therapy for individual COPD patients -- and select patients for clinical trials of new treatment options more precisely," says Fernando Martinez, M.D., M.S., an internal medicine professor who is also participated in the COPD Gene trial.

"PRM can also help to track COPD progression or response to treatment over time," says lead author Craig Gabán, assistant professor of radiology. 

"The PRM technique is a step forward in being able to better sub-classify patients with COPD so that targeted therapies can be developed," says co-author MeiLan Han, M.D. M.S., a U-M pulmonologist and COPD Gene investigator. "This is one of many important studies that is being made possible by the data being collected through NHLBI funded COPD initiatives."