CAD helps detect missed pulmonary embolism on CTPA

While CT pulmonary angiography (CTPA) can miss pulmonary embolism for a variety of reasons, the use of computer-aided-detection software can help physicians avoid these false negatives, according to a study published this month in the American Journal of Roentgenology.

In an article on, lead study author Seth Kligerman of the University of Maryland School of Medicine said that over the course of time he had noticed the problem with CTPA missing pulmonary emboli and decided to launch a study. Ultimately, he said he was not able to find any data about the false negatives.

Kligerman and colleagues reviewed more than 6,000 studies performed over a three-year period, finding 53 in which CTPA missed pulmonary emboli. They then assessed the effectiveness of a prototype CAD software for pulmonary embolism (PE-CAD) in detecting the missed emboli.

The program identified at least one PE in 41 of the 53 cases, at least one PE in 23 of 23 cases with multiple PEs, and 18 of 30 cases with a solitary PE. PE-CAD averaged 3.8 false-positive marks per case.

"Most [false-positive] marks are easily dismissed due to incorrect marking of a pulmonary vein, although it is possible that [false-positive] marks can lead to negative studies being incorrectly interpreted as positive," Kligerman told

Kligerman also noted, however, that the software is a prototype that has yet to receive clearance from the U.S. Food and Drug Administration.

"It is an amazing piece of technology and I wish I could use it in my clinical practice," he said. "If it were available, I would use it [as a second reader] on all CTPA studies initially interpreted as negative by the radiologist."

Providing appropriateness training to emergency department doctors ordering CT pulmonary angiography won't necessarily decrease inappropriate use of that test, according to research published last August in Academic Radiology.

To learn more:
- see the study in the American Journal of Roentgenology
- read the article in


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