title: Improved accuracy of pulmonary embolism computer-aided detection using iterative reconstruction compared with filtered back projection.
abstract: OBJECTIVE
  The purpose of this study was to determine whether use of iterative reconstruction (IR) can improve performance of a pulmonary embolism computer-aided detection (PE CAD) prototype.
  
  
  METHODS
  Images were collected from 40 consecutive pulmonary CT angiographic examinations in which PE was found and 26 studies in which it was not found for use as control cases. All images were reconstructed with filtered back projection (FBP) and six levels of a hybrid IR algorithm. The studies were evaluated with a prototype PE CAD system, and its performance was comparatively assessed on the basis of reconstruction type on a per-embolus and a per-study basis.
  
  
  RESULTS
  Use of the hybrid IR algorithm led to a significant and progressive decrease in false-positive marks made by PE CAD compared with those made by radiologists on FBP reconstructions (239 false-positive marks for FBP and 154, 136, 125, 116, 107, and 98 false-positive marks for the six hybrid IR [HIR] levels). Specificity improved with increasing HIR level (45.6% for level 6; 30.3% for FBP). However, compared with FBP, increasing levels of HIR resulted in a progressive decrease in per-embolism sensitivity (70.3% for FBP; 55.4% for HIR level 6) and, with the exception of HIR level 4, a progressive decrease in per-study sensitivity (97.5% for FBP; 85.0% for HIR level 6). Overall accuracy was highest for HIR level 1 (77.3%).
  
  
  CONCLUSIONS
  The use of IR leads to a significant reduction in false-positive marks by PE CAD at a cost of decreasing sensitivity. Very high levels of IR, which had the lowest sensitivities, should be avoided if being used concomitantly with PE CAD.
authors.affiliation: 1 All authors: Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland Medical Center, 22 S Greene St, Baltimore, MD 21201.
authors.forename: Kian
authors.initials: K
authors.lastname: Lahiji
authors.forename: Seth
authors.initials: S
authors.lastname: Kligerman
authors.forename: Jean
authors.initials: J
authors.lastname: Jeudy
authors.forename: Charles
authors.initials: C
authors.lastname: White
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D000792:Angiography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010363:Pattern Recognition, Automated / Q000379:methods*; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult
keywords: CT; computer-aided detection; iterative reconstruction; pulmonary embolism