title: Small Polyps at Endoluminal CT Colonography Are Often Seen But Ignored by Radiologists.
abstract: OBJECTIVE
  The objective of our study was to describe the characteristics of polyps viewed but then dismissed incorrectly by radiologists at endoluminal CT colonography (CTC), eye movements during these errors, and features provoking false-positive diagnoses.
  
  
  METHODS
  Forty-two radiologists viewed 30 endoluminal CTC videos, each depicting a polyp, while their eye movements were tracked. Half of the videos had computer-assisted detection (CAD), and half did not. Classification errors were defined when proven polyps were seen but dismissed. Eye movements during these errors and during correct polyp identifications were compared with multilevel modeling. Polyps were divided subsequently into "difficult to classify" and "easy to classify" using a classification error threshold of more than 15%. Polyp diameter, height, and subjective conspicuity and the proportion of time viewed were compared between groups.
  
  
  RESULTS
  Eye tracking revealed that 97% of false-negative polyp diagnoses were nonetheless preceded by the reader observing the polyp. The difficult polyps were significantly smaller than the easy polyps (mean diameter, 5.4 vs 8.2 mm, respectively p = 0.014) and were subjectively less conspicuous (median score, 4 vs 2; p = 0.0032). Readers spent proportionally less time viewing difficult polyps than viewing easy polyps (29.0% of the time they were on-screen vs 42.6%, respectively; p = 0.01) regardless of the presence of CAD.
  
  
  CONCLUSIONS
  Even small and subjectively inconspicuous polyps attract reader gaze, but they are nonetheless ignored. These errors are made rapidly even with CAD. Efforts to improve reader performance at CTC should focus on decision making rather than detection alone.
authors.affiliation: 1 Centre for Medical Imaging, University College London, 235 Euston Rd, Podium Level 2, London NW1 2BU, UK.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Plumb
authors.affiliation: 2 Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Fanshawe
authors.affiliation: 3 Health and Medical Sciences Group, University of Cumbria, Lancaster, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Phillips
authors.affiliation: 2 Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK.
authors.forename: Susan
authors.initials: S
authors.lastname: Mallett
authors.affiliation: 1 Centre for Medical Imaging, University College London, 235 Euston Rd, Podium Level 2, London NW1 2BU, UK.
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Taylor
authors.affiliation: 1 Centre for Medical Imaging, University College London, 235 Euston Rd, Podium Level 2, London NW1 2BU, UK.
authors.forename: Emma
authors.initials: E
authors.lastname: Helbren
authors.affiliation: 4 Post Graduate Medical Institute, Anglia Ruskin University, Chelmsford, UK.
authors.forename: Darren
authors.initials: D
authors.lastname: Boone
authors.affiliation: 1 Centre for Medical Imaging, University College London, 235 Euston Rd, Podium Level 2, London NW1 2BU, UK.
authors.forename: Steve
authors.initials: S
authors.lastname: Halligan
mesh_terms: D002983:Clinical Competence; D003111:Colonic Polyps / Q000175:diagnosis*; D023881:Colonography, Computed Tomographic; D003951:Diagnostic Errors; D005133:Eye Movements; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted; D012307:Risk Factors
keywords: 3D; CT colonography; colonic polyps; colorectal neoplasms; imaging; visual perception