Radiologists call for judicious use of CT for detecting pulmonary embolism

There has been a striking increase in the number of patients undergoing CT examinations of the chest to look for clots in the lung (pulmonary embolism) over recent years, especially through the emergency department, a study at one facility shows. This increased usage in combination with the radiation doses and the fact that new scanners can show previously undetectable abnormalities that may or may not affect treatment has radiologists calling for judicious ordering of the exam.

A new study, published in the October 2004 American Journal of Roentgenology, shows that during a nine-month period in 1997 –1998, 81 patients underwent CT for suspected pulmonary embolism through the emergency department at University Hospitals of Cleveland. That number increased to 349 during the corresponding nine-month interval in 2002-2003, said J. David Prologo, MD, lead author of the study and chief resident in radiology, University Hospitals.

The nearly five-fold increase in the number of patients who underwent CT for pulmonary embolism did not reflect a proportionate increase in the number of patients with the disease, however. In fact, only about 6% of patients in 2002-2003 had findings of pulmonary embolism, Dr. Prologo said. That compares to about 25% in 1997-1998.

Increased usage is due, in part, to the fact that CT is a noninvasive test that takes only "about 20 seconds to perform" and "can detect ancillary findings or findings indicative of an alternative diagnosis," said Dr. Prologo.

The increased number of scans being performed and the evolving technology of CT is allowing radiologists to see very small abnormalities that were not previously detectable. Often, this is resulting in the reconsideration of clinical issues, Dr. Prologo said. For example, clots in very small arteries in the lungs are now identifiable with CT. "It is not always clear, however, that these findings are responsible for the patient's symptoms or are a harbinger of future disease. Therefore, given the risk of treatment side effects as well as the time and cost commitment necessary for therapy, the decision to treat some patients becomes a difficult one," he said.

Because CT has become so widely accepted and available to referring physicians, they should be aware that these examinations mean radiation to the patient and potential detection of small abnormalities of uncertain significance, Dr. Prologo said. This study suggests that criteria should be developed so only patients who are most likely to benefit from these examinations would undergo CT, he said.

A PDF of the study is available to reporters.

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