Beginning 2 days before the laxative-free CT scan, patients ate a low-fiber diet that included a special material to “tag” their feces. After the CT scan was done, a computer program removed the feces from the pictures to allow a radiologist to look for suspicious lesions. Up to a few weeks later, each patient had a standard colonoscopy with the standard laxative preparation to remove feces. The results of the 2 studies were compared. The researchers also asked patients about their experiences with the tests.