Pulmonary CTA use for embolism diagnosis spikes

Referrals for pulmonary CT angiography have increased fivefold since the late 1990s at one Ohio institution. The modality's accessibility and ability to make alternative diagnoses have contributed to the rise, but the spike in demand also raises clinical questions.

In a study conducted at the University Hospitals of Cleveland, researchers identified both hospitalized and emergency room patients who had undergone CTA for suspected pulmonary embolism during one of two periods: 1997 to 1998 and 2002 to 2003. The patients were examined with single-slice CT with 3-mm collimation and a pitch of 1.7 and multislice CT with 2-mm collimation and a pitch of 1.

The number of pulmonary CTAs jumped from 81 patients in 1997 to 1998 to 349 in 2002 to 2003 (AJR Oct 2004; 183:1093-1096).

"These data demonstrate that clinicians have accepted the evidence regarding CT for PE and are incorporating it into their practices," said lead author Dr. John David Prologo, chief radiology resident at the University Hospitals.

CT's ability to detect ancillary findings andits increasing availability are leading to more referrals. Some physicians use the test to screen patients with suspected cardiothoracic disease, according to Prologo.

This could present a problem, as the exam introduces radiation into the target population, and the increased radiation may be unwarranted. Researchers reported a significant drop in findings of pulmonary embolism from 25% in 1997 to 1998 to 6% in 2002 to 2003.

A study presented at the American Roentgen Ray Society meeting in May found that young women may be receiving too much radiation when physicians rely on CT to make a diagnosis of pulmonary embolism. Researchers led by Dr. Mark S. Parker, an associate professor of thoracic radiology at the Medical College of Virginia, found that CT pulmonary angiograms can deliver more than three times the amount of radiation to the female breast as standard mammography exams.

The clinical implications of ancillary findings bring up further unanswered questions. The Cleveland study found that 13 of the positive scans in the more recent group had subsegmental embolism findings, a significant increase over the earlier time period. Whether these subsegmental emboli are responsible for a patient's symptoms and warrant treatment is not known, Prologo said.

"Patients with small/subsegmental emboli need to be divided into treated and untreated groups, and their outcomes with regard to recurrent thromboemboic disease need to be compared," he said.

For more information from the online Diagnostic Imaging archives:

Radiation dose challenges PE diagnosis in women

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MRI aids ventilation/ perfusion lung studies

CAD adds clarity to pulmonary embolism diagnosis