title: Characterizing search, recognition, and decision in the detection of lung nodules on CT scans: elucidation with eye tracking.
abstract: OBJECTIVE
  To determine the effectiveness of radiologists' search, recognition, and acceptance of lung nodules on computed tomographic (CT) images by using eye tracking.
  
  
  METHODS
  This study was performed with a protocol approved by the institutional review board. All study subjects provided informed consent, and all private health information was protected in accordance with HIPAA. A remote eye tracker was used to record time-varying gaze paths while 13 radiologists interpreted 40 lung CT images with an average of 3.9 synthetic nodules (5-mm diameter) embedded randomly in the lung parenchyma. The radiologists' gaze volumes ( GV gaze volume s) were defined as the portion of the lung parenchyma within 50 pixels (approximately 3 cm) of all gaze points. The fraction of the total lung volume encompassed within the GV gaze volume s, the fraction of lung nodules encompassed within each GV gaze volume (search effectiveness), the fraction of lung nodules within the GV gaze volume detected by the reader (recognition-acceptance effectiveness), and overall sensitivity of lung nodule detection were measured.
  
  
  RESULTS
  Detected nodules were within 50 pixels of the nearest gaze point for 990 of 992 correct detections. On average, radiologists searched 26.7% of the lung parenchyma in 3 minutes and 16 seconds and encompassed between 86 and 143 of 157 nodules within their GV gaze volume s. Once encompassed within their GV gaze volume , the average sensitivity of nodule recognition and acceptance ranged from 47 of 100 nodules to 103 of 124 nodules (sensitivity, 0.47-0.82). Overall sensitivity ranged from 47 to 114 of 157 nodules (sensitivity, 0.30-0.73) and showed moderate correlation (r = 0.62, P = .02) with the fraction of lung volume searched.
  
  
  CONCLUSIONS
  Relationships between reader search, recognition and acceptance, and overall lung nodule detection rate can be studied with eye tracking. Radiologists appear to actively search less than half of the lung parenchyma, with substantial interreader variation in volume searched, fraction of nodules included within the search volume, sensitivity for nodules within the search volume, and overall detection rate.
authors.affiliation: From the Duke Clinical Research Institute, Box 17969, 2400 Pratt St, Durham, NC 27715 (G.D.R., K.R.C.); Department of Radiology, Duke University School of Medicine, Durham, NC (G.D.R., J.E.R., M.T., B.H., S.B., D.M.S., L.M.H.); Department of Medical Imaging, University of Toronto, Toronto, ON, Canada (D.L.L.); and Department of Radiology, Stanford University School of Medicine, Stanford, Calif (S.N.).
authors.forename: Geoffrey D
authors.initials: GD
authors.lastname: Rubin
authors.forename: Justus E
authors.initials: JE
authors.lastname: Roos
authors.forename: Martin
authors.initials: M
authors.lastname: Tall
authors.forename: Brian
authors.initials: B
authors.lastname: Harrawood
authors.forename: Sukantadev
authors.initials: S
authors.lastname: Bag
authors.forename: Donald L
authors.initials: DL
authors.lastname: Ly
authors.forename: Danielle M
authors.initials: DM
authors.lastname: Seaman
authors.forename: Lynne M
authors.initials: LM
authors.lastname: Hurwitz
authors.forename: Sandy
authors.initials: S
authors.lastname: Napel
authors.forename: Kingshuk
authors.initials: K
authors.lastname: Roy Choudhury
mesh_terms: D002983:Clinical Competence; D003657:Decision Making; D005133:Eye Movements; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*