Virtual colonoscopy is also called CT colonography. CT stands for computed tomography. A CT scanner takes many X-rays of the colon that are processed by a computer. The computer puts all the X-rays together to create 3-D images of your colon and rectum. These images can then be looked at by your healthcare provider. Colorectal cancer screening using a method known as computed tomography (CT) colonography, also referred to as virtual colonoscopy, is a noninvasive technique for the early detection of precancerous polyps as well as the diagnosis of cancer that requires no sedation. Advantages of CTC for screening patients include its ability to reveal detailed information about the type of abnormal tissue found in a noninvasive manner.