Helium Imaging Detects Emphysema Changes In Smallest Airways Of Lung

The technique, known as helium-3 diffusion magnetic resonance imaging (3He diffusion MRI) is more sensitive than computed tomography (CT) or any other imaging method currently available for examining the lung. The findings were published in the Proceedings of the National Academy of Sciences. The lead author is Dmitriy A. Yablonskiy, Ph.D., a professor of physics and an assistant professor of radiology at the School of Medicine’s Mallinckrodt Institute of Radiology.

“Our findings suggest this may be a new means for the early detection of emphysema by demonstrating the enlargement of the air spaces in the lung,” says Stephen S. Lefrak, M.D., professor of medicine and a co-author of the paper. “I suspect it also will help in understanding the development, evolution, progression and physiological effects of many lung diseases including emphysema, asthma and perhaps pulmonary fibrosis.”

Joel D. Cooper, M.D., Evarts A. Graham Professor of Surgery and head of the Division of Cardiothoracic Surgery added, “This technique may well help us refine our selection criteria and better predict the outcome of emphysema patients undergoing lung-volume reduction surgery.” Lung reduction surgery involves the removal of the most diseased areas of the lung in select patients.

3He diffusion MRI uses a nonradioactive and highly polarized – hyperpolarized – form of helium gas. Hyperpolarizing the gas, which is done using lasers, makes the helium detectable by MRI.

To perform the technique, a patient in an MRI machine inhales the gas and holds his or her breath for ten seconds. The resulting image shows how far the atoms of helium travel, or diffuse, within the lungs during a period of two thousandths of a second. The method reveals the distance traveled both along and across the airways.

These distances are recorded as colors ranging from red (the smallest distances) to violet (the largest distances). This information also indicates the physical diameter of the airways and of the alveoli.

If a large space is available, the helium molecules can move freely and travel relatively far. This is the case in the trachea, the relatively large tube that carries air from the mouth and nose into the chest and shows up as violet when imaged. In small airways within healthy lungs, the bronchioles and alveoli, the helium atoms have little room to move. These areas show up in the image as red or deep orange.