title: Unsuspected pulmonary embolism: prospective detection on routine helical CT scans.
abstract: OBJECTIVE
  To determine the prevalence of unsuspected pulmonary embolism (PE) on routine thoracic helical computed tomographic (CT) scans and to quantify the improvement in PE detection by using a cine-paging mode on a workstation instead of hard-copy review.
  
  
  METHODS
  Seven hundred eighty-five patients referred for routine contrast medium-enhanced thoracic CT within 9 months were prospectively recruited. Helical CT was performed. Studies were prospectively interpreted by four radiologists. Two radiologists performed routine, undirected, hard-copy consensus review for official interpretation; two of three thoracic radiologists independently performed a dedicated workstation-based search for PE. The presence of PE involving the main, lobar, or segmental pulmonary arteries was assigned a score of 1-5 (1 = definitely negative, 5 = definitely positive) by each independent reviewer. Patients with a score of 4 or 5 underwent lower-extremity ultrasound, ventilation-perfusion scintigraphy, or both, followed by pulmonary CT angiography if the findings were still equivocal.
  
  
  RESULTS
  Twelve (1.5%) of the 785 patients had unsuspected PE, with an inpatient prevalence of 5% (eight of 160) and an outpatient prevalence of 0.6% (four of 625). Of the 12 patients with unsuspected PE, 10 (83%) had cancer. Of the 81 inpatients with cancer, seven (9%) had unsuspected PE. A dedicated workstation-based search resulted in detection of PE in three more patients (25%) than did hard-copy interpretation.
  
  
  CONCLUSIONS
  The prevalence of unsuspected PE was highest among inpatients with cancer. A directed, workstation-based search can improve the PE detection rate over that with hard-copy review.
authors.affiliation: Department of Radiology, Stanford University School of Medicine, CA 94305-5105, USA.
authors.forename: M V
authors.initials: MV
authors.lastname: Gosselin
authors.forename: G D
authors.initials: GD
authors.lastname: Rubin
authors.forename: A N
authors.initials: AN
authors.lastname: Leung
authors.forename: J
authors.initials: J
authors.lastname: Huang
authors.forename: N W
authors.initials: NW
authors.lastname: Rizk
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography; D001158:Arteries; D002933:Cineradiography; D003199:Computer Systems; D003287:Contrast Media; D005260:Female; D006760:Hospitalization; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007472:Iohexol; D007479:Iopamidol; D008168:Lung / Q000098:blood supply / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications; D015588:Observer Variation; D010045:Outpatients; D015995:Prevalence; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D011856:Radiographic Image Enhancement; D011877:Radionuclide Imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014463:Ultrasonography; D014692:Ventilation-Perfusion Ratio
chemical_list: D003287:Contrast Media; D007472:Iohexol; D007479:Iopamidol