title: CT colonography: computer-assisted detection of colorectal cancer.
abstract: OBJECTIVE
  Computer-aided detection (CAD) for CT colonography (CTC) has been developed to detect benign polyps in asymptomatic patients. We aimed to determine whether such a CAD system can also detect cancer in symptomatic patients.
  
  
  METHODS
  CTC data from 137 symptomatic patients subsequently proven to have colorectal cancer were analysed by a CAD system at 4 different sphericity settings: 0, 50, 75 and 100. CAD prompts were classified by an observer as either true-positive if overlapping a cancer or false-positive if elsewhere. Colonoscopic data were used to aid matching.
  
  
  RESULTS
  Of 137 cancers, CAD identified 124 (90.5%), 122 (89.1%), 119 (86.9%) and 102 (74.5%) at a sphericity of 0, 50, 75 and 100, respectively. A substantial proportion of cancers were detected on either the prone or supine acquisition alone. Of 125 patients with prone and supine acquisitions, 39.3%, 38.3%, 43.2% and 50.5% of cancers were detected on a single acquisition at a sphericity of 0, 50, 75 and 100, respectively. CAD detected three cancers missed by radiologists at the original clinical interpretation. False-positive prompts decreased with increasing sphericity value (median 65, 57, 45, 24 per patient at values of 0, 50, 75, 100, respectively) but many patients were poorly prepared.
  
  
  CONCLUSIONS
  CAD can detect symptomatic colorectal cancer but must be applied to both prone and supine acquisitions for best performance.
authors.affiliation: Centre for Medical Imaging, University College Hospital, London, UK.
authors.forename: C
authors.initials: C
authors.lastname: Robinson
authors.forename: S
authors.initials: S
authors.lastname: Halligan
authors.forename: G
authors.initials: G
authors.lastname: Iinuma
authors.forename: W
authors.initials: W
authors.lastname: Topping
authors.forename: S
authors.initials: S
authors.lastname: Punwani
authors.forename: L
authors.initials: L
authors.lastname: Honeyfield
authors.forename: S A
authors.initials: SA
authors.lastname: Taylor
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003111:Colonic Polyps / Q000000981:diagnostic imaging*; D023881:Colonography, Computed Tomographic / Q000379:methods*; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D055815:Young Adult