Using the teniae coli as a registration tool in CT colonography

We have found greater difficulty achieving desirable sensitivities and specificities with our computer-aided detection (CAD) system on polyps sized 6-9 mm. Missed polyps in our ground truth CAD training datasets could be one possible cause. Most CT colonography (CTC) protocols require supine and prone scans therefore the number of polyps visible to a radiologist in at least one scan may increase. However, registration of a specific polyp visible in both scans can prove difficult without a uniform coordinate system. Using a teniae coli registration tool we hypothesized we could register and find a statistically significant number of 6-9 mm polyps believed to be not findable in one scan subsequently reducing error in the training data and enabling better training of our CAD system. Database queries yielded 20 polyps initially believed to be not findable in one scan. The teniae coli navigation and registration system allowed us to identify 30% (6/20) of the polyps as matches with confidence in both scans (rating 1) and 10% (2/20) of the polyps with a potential match with some uncertainty (rating 2). No convincing match was found for 60% (12/20) of polyps (rating 3). We conclude that this teniae coli registration tool is an effective means of identifying and reducing ground truth data errors in 6-9 mm polyps initially believed not findable in one scan. The use of this tool has the potential to improve the performance of a CAD system on the more difficult 6-9 mm polyps.