Success of a safe and simple algorithm to reduce use of CT pulmonary angiography in the emergency department

AJR Am J Roentgenol. 2010 Feb;194(2):392-7. doi: 10.2214/AJR.09.2499.


Objective: The purpose of our study was to determine whether the radiation exposure to patients with suspected pulmonary embolism (PE) could be decreased by safely increasing the use of ventilation-perfusion (V/Q) scanning and decreasing the use of CT pulmonary angiography (CTPA) through an educational intervention.

Materials and methods: Collaborative educational seminars were held among the radiology, nuclear medicine, and emergency medicine departments in December 2006 and January 2007 regarding the radiation dose and accuracies of V/Q scanning and CTPA for diagnosing PE. To reduce radiation exposure, an imaging algorithm was introduced in which emergency department patients with a clinical suspicion of PE underwent chest radiography. If the chest radiograph was normal, V/Q scanning was recommended, otherwise CTPA was recommended. We retrospectively tallied the number and results of CTPA and V/Q scanning and calculated mean radiation effective dose before and after the intervention. False-negative findings were defined as subsequent thromboembolism within 90 days.

Results: The number of CTPA examinations performed decreased from 1,234 in 2006 to 920 in 2007, and the number of V/Q scans increased from 745 in 2006 to 1,216 in 2007. The mean effective dose was reduced by 20%, from 8.0 mSv in 2006 to 6.4 mSv in 2007 (p < 0.0001). The patients who underwent CTPA and V/Q scanning in 2006 were of similar age. In 2007, the patients who underwent V/Q scanning were significantly younger. There was no significant difference in the false-negative rate (range, 0.8-1.2%) between CTPA and V/Q scanning in 2006 and 2007.

Conclusion: The practice patterns of physicians changed in response to an educational intervention, resulting in a reduction in radiation exposure to emergency department patients with suspected PE without compromising patient safety.

MeSH terms

  • Algorithms*
  • Angiography*
  • Chi-Square Distribution
  • Contrast Media
  • False Negative Reactions
  • Female
  • Gadolinium DTPA
  • Humans
  • Inservice Training
  • Male
  • Middle Aged
  • Pulmonary Embolism / diagnostic imaging*
  • Pulmonary Medicine / education*
  • Radiation Dosage
  • Radiation Injuries / prevention & control*
  • Radiographic Image Interpretation, Computer-Assisted
  • Radiology / education*
  • Retrospective Studies
  • Tomography, X-Ray Computed*
  • Treatment Outcome


  • Contrast Media
  • Gadolinium DTPA