title: Polyp measurement based on CT colonography and colonoscopy: variability and systematic differences.
abstract: OBJECTIVE
  To assess the variability and systematic differences in polyp measurements on optical colonoscopy and CT colonography.
  
  
  METHODS
  Gastroenterologists measured 51 polyps by visual estimation, forceps comparison and linear probe. CT colonography observers randomly assessed polyp size two-dimensionally (abdominal and intermediate window) and three-dimensionally (manually and semi-automatically). Linear mixed models were used to assess the variability and systematic differences between CT colonography and optical colonoscopy techniques.
  
  
  RESULTS
  The variability of forceps and linear probe measurements was comparable and both showed less variability than measurement by visual assessment. Measurements by linear probe were 0.7 mm smaller than measurements by visual assessment or by forceps. The variability of all CT colonography techniques was lower than for measurements by forceps or visual assessment and sometimes lower (only 2D intermediate window and manual 3D) compared with measurements by linear probe. All CT colonography measurements judged polyps to be larger than optical colonoscopy, with differences ranging from 0.7 to 2.3 mm.
  
  
  CONCLUSIONS
  A linear probe does not reduce the measurement variability of endoscopists compared with the forceps. Measurement differences between observers on CT colonography were usually smaller than at optical colonoscopy. Polyps appeared larger when using various CT colonography techniques than when measured during optical colonoscopy.
authors.affiliation: Department of Radiology, Academic Medical Centre, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. Ayso.devries@amc.uva.nl
authors.forename: Ayso H
authors.initials: AH
authors.lastname: de Vries
authors.forename: Shandra
authors.initials: S
authors.lastname: Bipat
authors.forename: Evelien
authors.initials: E
authors.lastname: Dekker
authors.forename: Marjolein H
authors.initials: MH
authors.lastname: Liedenbaum
authors.forename: Jasper
authors.initials: J
authors.lastname: Florie
authors.forename: Paul
authors.initials: P
authors.lastname: Fockens
authors.forename: Roel
authors.initials: R
authors.lastname: van der Kraan
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Mathus-Vliegen
authors.forename: Johannes B
authors.initials: JB
authors.lastname: Reitsma
authors.forename: Roel
authors.initials: R
authors.lastname: Truyen
authors.forename: Frans M
authors.initials: FM
authors.lastname: Vos
authors.forename: Aeilko H
authors.initials: AH
authors.lastname: Zwinderman
authors.forename: Jaap
authors.initials: J
authors.lastname: Stoker
mesh_terms: D000368:Aged; D003111:Colonic Polyps / Q000175:diagnosis*; D023881:Colonography, Computed Tomographic / Q000379:methods*; D003113:Colonoscopy / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity