title: Comparison of axial, coronal, and primary 3D review in MDCT colonography for the detection of small polyps: a phantom study.
abstract: OBJECTIVE
  The purpose of this phantom study is to compare the influence of the reading technique (axial images alone in comparison to 3D endoluminal, coronal, and combined 2D/3D review methods) on the sensitivity and inter-reader variability with MDCT colonography for the detection of small colonic polyps.
  
  
  METHODS
  An anthropomorphic pig colon phantom with 75 randomly distributed simulated small polyps of 2-8mm size, was distended with air and scanned in a water phantom using multidetector-row CT with 4mm x 1mm collimation. Three radiologists rated the presence of polyps on a five-point scale. Performance with axial sections alone was compared to the performance with coronal sections, virtual endoscopy (VE), and a combined 2D/3D approach. We calculated sensitivities for polyp detection and used ROC analysis for data evaluation.
  
  
  RESULTS
  There was no significant difference between the mean area under the curve (A(z)) for axial images and VE (A(z)=0.934 versus 0.932), whereas coronal images were significantly inferior (A(z)=0.876) to both. The combined 2D/3D approach yielded the best results, with an A(z) of 0.99. Differences in sensitivity between individual readers were significant in axial images (sensitivity, 75-93%, p=0.001) and coronal images (sensitivity, 69-80%, p=0.028), but became non-significant with VE (83-88%, p=0.144) and the combined 2D/3D approach (95-97%, p=0.288).
  
  
  CONCLUSIONS
  Evaluation of axial sections alone leads to significant differences in detection rates between individual observers. A combined 2D/3D evaluation improves sensitivities for polyp detection and reduces inter-individual differences to an insignificant level.
authors.affiliation: Department of Radiology, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria. thomas.mang@meduniwien.ac.at
authors.forename: Thomas
authors.initials: T
authors.lastname: Mang
authors.forename: Cornelia
authors.initials: C
authors.lastname: Schaefer-Prokop
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schima
authors.forename: Andrea
authors.initials: A
authors.lastname: Maier
authors.forename: Ewald
authors.initials: E
authors.lastname: Schober
authors.forename: Christina
authors.initials: C
authors.lastname: Mueller-Mang
authors.forename: Michael
authors.initials: M
authors.lastname: Weber
authors.forename: Mathias
authors.initials: M
authors.lastname: Prokop
mesh_terms: D000465:Algorithms; D003111:Colonic Polyps / Q000000981:diagnostic imaging*; D023881:Colonography, Computed Tomographic / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*