Computer aided detection of polyps in virtual colonoscopy with Sameday faecal tagging

One of the key factors which may lead to a greater patient compliance in virtual colonoscopy is a well tolerated bowel preparation; there is evidence that this may be obtained by faecal tagging techniques. In so-called "sameday faecal tagging" (SDFT) preparations, iodine contrast material is administered on the day of the exam in a hospital ward. The administration of oral contrast on the day of the procedure, however, often results in a less homogenous marking of faecal residues and computer aided-detection (CAD) systems must be able to treat these kinds of preparations. The aim of this work is to present a CAD scheme capable of achieving good performances on CT datasets obtained using SDFT, both in terms of sensitivity and specificity. The electronically cleansed datasets is processed by a scheme composed of three steps: colon surface extraction, polyp candidate segmentation through curvature-based features and discrimination between true polyps and false alarms. The system was evaluated on a dataset including 102 patients from three different centers. A specificity of 8.2 false positives per scan was obtained at a 100% sensitivity for polyps larger than 10 mm. In conclusion CAD schemes for SDFT may be designed to obtain high performances.