title: Pulmonary nodules on multi-detector row CT scans: performance comparison of radiologists and computer-aided detection.
abstract: OBJECTIVE
  To compare the performance of radiologists and of a computer-aided detection (CAD) algorithm for pulmonary nodule detection on thin-section thoracic computed tomographic (CT) scans.
  
  
  METHODS
  The study was approved by the institutional review board. The requirement of informed consent was waived. Twenty outpatients (age range, 15-91 years; mean, 64 years) were examined with chest CT (multi-detector row scanner, four detector rows, 1.25-mm section thickness, and 0.6-mm interval) for pulmonary nodules. Three radiologists independently analyzed CT scans, recorded the locus of each nodule candidate, and assigned each a confidence score. A CAD algorithm with parameters chosen by using cross validation was applied to the 20 scans. The reference standard was established by two experienced thoracic radiologists in consensus, with blind review of all nodule candidates and free search for additional nodules at a dedicated workstation for three-dimensional image analysis. True-positive (TP) and false-positive (FP) results and confidence levels were used to generate free-response receiver operating characteristic (ROC) plots. Double-reading performance was determined on the basis of TP detections by either reader.
  
  
  RESULTS
  The 20 scans showed 195 noncalcified nodules with a diameter of 3 mm or more (reference reading). Area under the alternative free-response ROC curve was 0.54, 0.48, 0.55, and 0.36 for CAD and readers 1-3, respectively. Differences between reader 3 and CAD and between readers 2 and 3 were significant (P < .05); those between CAD and readers 1 and 2 were not significant. Mean sensitivity for individual readings was 50% (range, 41%-60%); double reading resulted in increase to 63% (range, 56%-67%). With CAD used at a threshold allowing only three FP detections per CT scan, mean sensitivity was increased to 76% (range, 73%-78%). CAD complemented individual readers by detecting additional nodules more effectively than did a second reader; CAD-reader weighted kappa values were significantly lower than reader-reader weighted kappa values (Wilcoxon rank sum test, P < .05).
  
  
  CONCLUSIONS
  With CAD used at a level allowing only three FP detections per CT scan, sensitivity was substantially higher than with conventional double reading.
authors.affiliation: Department of Radiology, Stanford University School of Medicine, 300 Pasteur Drive, S-072, Stanford, CA 94305-5105, USA. grubin@stanford.edu
authors.forename: Geoffrey D
authors.initials: GD
authors.lastname: Rubin
authors.forename: John K
authors.initials: JK
authors.lastname: Lyo
authors.forename: David S
authors.initials: DS
authors.lastname: Paik
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Sherbondy
authors.forename: Lawrence C
authors.initials: LC
authors.lastname: Chow
authors.forename: Ann N
authors.initials: AN
authors.lastname: Leung
authors.forename: Robert
authors.initials: R
authors.lastname: Mindelzun
authors.forename: Pamela K
authors.initials: PK
authors.lastname: Schraedley-Desmond
authors.forename: Steven E
authors.initials: SE
authors.lastname: Zinck
authors.forename: David P
authors.initials: DP
authors.lastname: Naidich
authors.forename: Sandy
authors.initials: S
authors.lastname: Napel
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D003936:Diagnosis, Computer-Assisted; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted; D013902:Radiography, Thoracic; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed