Gastrointestinal

European Radiology

, Volume 16, Issue 8, pp 1737-1744

Polyp measurement and size categorisation by CT colonography: effect of observer experience in a multi-centre setting

  • David BurlingAffiliated withIntestinal Imaging Centre, St. Marks Hospital
  • , Steve HalliganAffiliated withSpecialist Radiology, Level 2 Podium, University College Hospital Email author 
  • , Douglas G. AltmanAffiliated withCentre for Medical Statistics
  • , Wendy AtkinAffiliated withCancer Research UK, St Mark’s Hospital
  • , Clive BartramAffiliated withIntestinal Imaging Centre, St. Marks Hospital
  • , Helen FenlonAffiliated withMater Misericordiae
  • , Andrea LaghiAffiliated withLa Sapienza
  • , Jaap StokerAffiliated withAmersterdam Medican Centre
  • , Stuart TaylorAffiliated withSpecialist Radiology, Level 2 Podium, University College Hospital
    • , Roger FrostAffiliated withSalisbury District Hospital
    • , Guido DesseyAffiliated withStedelijk Ziekenhuis
    • , Melinda De VilliersAffiliated withIntestinal Imaging Centre, St. Marks Hospital
    • , Jasper FlorieAffiliated withAmersterdam Medican Centre
    • , Shane FoleyAffiliated withMater Misericordiae
    • , Lesley HoneyfieldAffiliated withIntestinal Imaging Centre, St. Marks Hospital
    • , Riccardo IannacconeAffiliated withLa Sapienza
    • , Teresa GalloAffiliated withIntestinal Imaging Centre, St. Marks HospitalCandiolo Oncologic Hospital
    • , Clive KayAffiliated withIntestinal Imaging Centre, St. Marks HospitalBradford Royal Infirmary
    • , Philippe LefereAffiliated withStedelijk Ziekenhuis
    • , Andrew LoweAffiliated withIntestinal Imaging Centre, St. Marks HospitalBradford Royal Infirmary
    • , Filipo MangiapaneAffiliated withLa Sapienza
    • , Jesse MarrannesAffiliated withStedelijk Ziekenhuis
    • , Emmanuele NeriAffiliated withIntestinal Imaging Centre, St. Marks HospitalUniversity of Pisa
    • , Giulia NiedduAffiliated withIntestinal Imaging Centre, St. Marks HospitalCandiolo Oncologic Hospital
    • , David NicholsonAffiliated withIntestinal Imaging Centre, St. Marks HospitalHope Hospital
    • , Alan O’HareAffiliated withMater Misericordiae
    • , Sante OriAffiliated withLa Sapienza
    • , Benedetta PolitiAffiliated withIntestinal Imaging Centre, St. Marks HospitalUniversity of Pisa
    • , Martin PoulusAffiliated withAmersterdam Medican Centre
    • , Daniele ReggeAffiliated withIntestinal Imaging Centre, St. Marks HospitalCandiolo Oncologic Hospital
    • , Lisa RenautAffiliated withIntestinal Imaging Centre, St. Marks HospitalHope Hospital
    • , Velauthan RudralinghamAffiliated withIntestinal Imaging Centre, St. Marks HospitalHope Hospital
    • , Saverio SignorettaAffiliated withIntestinal Imaging Centre, St. Marks HospitalCandiolo Oncologic Hospital
    • , Paola VagliAffiliated withIntestinal Imaging Centre, St. Marks HospitalUniversity of Pisa
    • , Victor Van der HulstAffiliated withAmersterdam Medican Centre
    • , Jane Williams-ButtAffiliated withIntestinal Imaging Centre, St. Marks HospitalBradford Royal Infirmary

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Abstract

The extent measurement error on CT colonography influences polyp categorisation according to established management guidelines is studied using twenty-eight observers of varying experience to classify polyps seen at CT colonography as either ‘medium’ (maximal diameter 6-9 mm) or ‘large’ (maximal diameter 10 mm or larger). Comparison was then made with the reference diameter obtained in each patient via colonoscopy. The Bland-Altman method was used to assess agreement between observer measurements and colonoscopy, and differences in measurement and categorisation was assessed using Kruskal-Wallis and Chi-squared test statistics respectively. Observer measurements on average underestimated the diameter of polyps when compared to the reference value, by approximately 2–3 mm, irrespective of observer experience. Ninety-five percent limits of agreement were relatively wide for all observer groups, and had sufficient span to encompass different size categories for polyps. There were 167 polyp observations and 135 (81%) were correctly categorised. Of the 32 observations that were miscategorised, 5 (16%) were overestimations and 27 (84%) were underestimations (i.e. large polyps misclassified as medium). Caution should be exercised for polyps whose colonographic diameter is below but close to the 1-cm boundary threshold in order to avoid potential miscategorisation of advanced adenomas.

Keywords

CT colon Computerised tomography Virtual colonoscopy