Radiology: Volume 273: Number 3—December 2014 n radiology.rsna.org 783 ORIGINAL RESEARCH n GASTROINTESTINAL IMAGING 1 From the Department of Primary Care Health Sciences, University of Oxford, Radcliffe Observatory Quarter, Woodstock Road, Oxford OX2 6GG, England (S.M., T.R.F.); Health and Medical Sciences Group, University of Cumbria, Lancaster, England (P.P.); Centre for Medical Imaging, University College London, London, England (E.H., S.A.T., S.H., D.B.); Applied Vision Research Centre, Loughbor- ough University, Loughborough, England (A.G.); School of Medicine, Lancaster University, Lancaster, England (D.M.); and Centre for Statistics in Medicine, University of Oxford, Oxford, England (D.G.A.). Received December 18, 2013; revision requested February 4, 2014; revision received March 24; accepted April 22; final version accepted April 29. Supported by a UK National Institute for Health Research (NIHR) Programme Grant for Applied Research (grant RP-PG-0407-10338). Address correspondence to S.M. (e-mail: susan.mallett@phc.ox.ac.uk). q RSNA, 2014 Purpose: To identify and compare key stages of the visual process in experienced and inexperienced readers and to examine how these processes are used to search a moving three- dimensional (3D) image and their relationship to false- negative errors. Materials and Methods: Institutional review board research ethics approval was granted to use anonymized computed tomographic (CT) colonographic data from previous studies and to obtain eye- tracking data from volunteers. Sixty-five radiologists (27 experienced, 38 inexperienced) interpreted 23 endolumi- nal 3D CT colonographic videos. Eye movements were re- corded by using eye tracking with a desk-mounted tracker. Readers indicated when they saw a polyp by clicking a com- puter mouse. Polyp location and boundary on each video frame were quantified and gaze data were related to the polyp boundary for each individual reader and case. Pre- defined metrics were quantified and used to describe and compare visual search patterns between experienced and inexperienced readers by using multilevel modeling. Results: Time to first pursuit was significantly shorter in experi- enced readers (hazard ratio, 1.22 [95% confidence inter- val: 1.04, 1.44]; P = .017) but other metrics were not significantly different. Regardless of expertise, metrics such as assessment, identification period, and pursuit times were extended in videos where polyps were visible on screen for longer periods of time. In 97% (760 of 787) of observations, readers correctly pursued polyps. Conclusion: Experienced readers had shorter time to first eye pur- suit, but many other characteristics of eye tracking were similar between experienced and inexperienced readers. Readers pursued polyps in 97% of observations, which indicated that errors during interpretation of 3D CT colo- nography in this study occurred in either the discovery or the recognition phase, but rarely in the scanning phase of radiologic image inspection. q RSNA, 2014 Susan Mallett, DPhil Peter Phillips, PhD Thomas R. Fanshawe, PhD Emma Helbren, FRCR Darren Boone, MRCS, FRCR Alastair Gale, PhD Stuart A. Taylor, MB BS, MD, MRCP, FRCR David Manning, DSc Douglas G. Altman, DSc Steve Halligan, MB, BS, MD, FRCP, FRCR Tracking Eye Gaze during Interpretation of Endoluminal Three-dimensional CT Colonography: Visual Perception of Experienced and Inexperienced Readers 1 Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights.