Pulmonary CT fine-tunes treatments in emphysema

Pulmonary CT is helping pinpoint patients most likely to benefit from new minimally invasive therapies for emphysema, the fourth leading cause of death in the U.S.

The pulmonary disease is "incredibly common and largely underdiagnosed," said Dr. Jeffrey Mendel, chair of radiology at Caritas St. Elizabeth's Medical Center in Boston, during a presentation at the 8th Annual International Symposium on Multidetector-Row CT in June.

Minimally invasive therapies are emerging that may allow treatment without surgery. But to make use of these therapies, optimal patient selection requires accurate assessment of the emphysema. Chest x-rays are not up to the task, and manual methods are too time-consuming and user-dependent.

Enter CT. CT morphometry is a quantitative analytic technique for measuring emphysematous changes.

"How much emphysema is there? And how much is there compared with past scans? That is where quantification helps," Mendel said.

Tabular data on CT provide total lung volume, right and left lung volume, and the ratio of emphysema volume to lung volume. Three-D visual displays offer rapid visual assessment of complex data. The images are clinician-friendly and make it easy to compare patients' global disease over time. Mendel noted that symptoms of emphysema can be improved in few ways: rehab, pharmacotherapy, and lung transplantation.

Options to improve survival include smoking cessation, use of oxygen if hypoxic and for appropriate candidates, or lung volume reduction surgery whereby the damaged bits of tissue are removed. Lung volume reduction has traditionally been achieved through open chest surgery, but researchers have recently been developing means of reducing volume with a range of minimally invasive techniques.

"We are hoping lung volume reduction via bronchoscopic methods will improve survival. This is an important goal," Mendel said.

Direct injection of an agent that causes gradual collapse of affected segments of the lung shows promise and is currently being tested in clinical trials. It's important to select the right patients for this treatment, however. Those most likely to respond have inhomogeneous emphysema, upper lobe predominance, and poor overall lung function. So far, the treatment has seen results comparable to surgery, but long-term data are required to determine if it improves survival rates, he said.

Pharmacotherapy also looks promising. Interesting research has emerged with the use of retinoic acid in shrinking emphysema and encouraging growth of normal lung, Mendel said.

"There are a lot of exciting opportunities for us to help diagnose and stratify treatment for patients subjected to the fourth leading cause of death in this country," he said. "For those of us who do pulmonary CT, this is the future. It is a very exciting time to be doing this."

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