title: Assessment of radiologist performance in the detection of lung nodules: dependence on the definition of "truth".
abstract: OBJECTIVE
  Studies that evaluate the lung nodule detection performance of radiologists or computerized methods depend on an initial inventory of the nodules within the thoracic images (the "truth"). The purpose of this study was to analyze (1) variability in the "truth" defined by different combinations of experienced thoracic radiologists and (2) variability in the performance of other experienced thoracic radiologists based on these definitions of "truth" in the context of lung nodule detection in computed tomographic (CT) scans.
  
  
  METHODS
  Twenty-five thoracic CT scans were reviewed by four thoracic radiologists, who independently marked lesions they considered to be nodules >or=3 mm in maximum diameter. Panel "truth" sets of nodules were then derived from the nodules marked by different combinations of two and three of these four radiologists. The nodule detection performance of the other radiologists was evaluated based on these panel "truth" sets.
  
  
  RESULTS
  The number of "true" nodules in the different panel "truth" sets ranged from 15 to 89 (mean 49.8 +/- 25.6). The mean radiologist nodule detection sensitivities across radiologists and panel "truth" sets for different panel "truth" conditions ranged from 51.0 to 83.2%; mean false-positive rates ranged from 0.33 to 1.39 per case.
  
  
  CONCLUSIONS
  Substantial variability exists across radiologists in the task of lung nodule identification in CT scans. The definition of "truth" on which lung nodule detection studies are based must be carefully considered, because even experienced thoracic radiologists may not perform well when measured against the "truth" established by other experienced thoracic radiologists.
authors.affiliation: Department of Radiology, University of Chicago, Chicago, IL 60637, USA. s-armato@uchicago.edu
authors.forename: Samuel G
authors.initials: SG
authors.lastname: Armato
authors.forename: Rachael Y
authors.initials: RY
authors.lastname: Roberts
authors.forename: Masha
authors.initials: M
authors.lastname: Kocherginsky
authors.forename: Denise R
authors.initials: DR
authors.lastname: Aberle
authors.forename: Ella A
authors.initials: EA
authors.lastname: Kazerooni
authors.forename: Heber
authors.initials: H
authors.lastname: Macmahon
authors.forename: Edwin J R
authors.initials: EJ
authors.lastname: van Beek
authors.forename: David
authors.initials: D
authors.lastname: Yankelevitz
authors.forename: Geoffrey
authors.initials: G
authors.lastname: McLennan
authors.forename: Michael F
authors.initials: MF
authors.lastname: McNitt-Gray
authors.forename: Charles R
authors.initials: CR
authors.lastname: Meyer
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Reeves
authors.forename: Philip
authors.initials: P
authors.lastname: Caligiuri
authors.forename: Leslie E
authors.initials: LE
authors.lastname: Quint
authors.forename: Baskaran
authors.initials: B
authors.lastname: Sundaram
authors.forename: Barbara Y
authors.initials: BY
authors.lastname: Croft
authors.forename: Laurence P
authors.initials: LP
authors.lastname: Clarke
mesh_terms: D000328:Adult; D000368:Aged; D016477:Artifacts; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011361:Professional Competence; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*