Comparison of axial, coronal, and primary 3D review in MDCT colonography for the detection of small polyps: A phantom study

Purpose: 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 2-8 mm size, was distended with air and scanned in a water phantom using multidetector-row CT with 4 mm x 1 mm 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). Conclusion: 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. (C) 2008 Elsevier Ireland Ltd. All rights reserved.