Computed Tomography (CT) Colonography Versus Optical Colonoscopy

This study is designed to compare traditional Colonoscopy with CT Colonography, commonly known as "virtual colonoscopy". The study will compare the ability of both procedures as screening tests to identify polyps in the colon in patients at average risk for developing polyps. The patient preferences for each procedure will be assessed by means of a standardized questionnaire. As well the ability observers with differing levels of experience to read the CT scans and detect polyps will be compared. All patients will receive both CT scans and traditional colonoscopy on the same day.