Pulmonary embolism, a condition where there is a sudden and potentially deadly blockage in the lung artery, affects an estimated 600,000 Americans each year. Thus, pulmonary embolism is the fourth most commonly occurring cardiovascular problem in the United States.

To accurately diagnose pulmonary embolism, physicians should not only conduct a chest CT angiogram but also extend the scan to the legs, where the clots typically originate. The study using this method was reported in the June 1, 2006, issue of the New England Journal of Medicine.

The researchers recommend that physicians consider additional test results before ruling out pulmonary embolism in patients whose scan does not detect clots but whose clinical assessment suggests a high likelihood of pulmonary embolism.

"This study suggests that chest CT angiogram for detecting dangerous blood clots in the lung is good, but sometimes it is not enough," noted Paul D. Stein, MD, director of research education at St. Joseph Mercy Oakland Hospital in Pontiac, Michigan, professor of medicine at Wayne State University, and lead author of the paper. "We can more accurately detect or rule out pulmonary embolism by taking pictures of the leg veins in addition to pictures of the lung arteries."

Read more at the National Heart, Lung, and Blood Institute.