Imaging tests are also used to screen for and detect colorectal cancer. These tests use technologies that visualize your body organs and present them like a picture. Imaging tests are also used to determine how far the cancer has spread or how well it is responding, or has responded, to treatment. While some tests still use X-rays, newer technologies use radioactivity (in very tiny doses), ultrasound, or magnetic fields to obtain the pictures.
Inside your abdominal cavity is the long, tubular digestive tract. The second part of this tube -- the large intestine -- is composed of the colon, which stretches 4 feet to 6 feet, and the rectum, which is only 4 inches to 6 inches long.
The inner lining of this "colorectal tube" can be a fertile breeding ground for small tumors, called polyps (Figure 1). About a quarter of all adults in the U.S. older than age 50 will have at least one colorectal polyp. Most colorectal cancers develop from polyps...
New technology has made it possible for a computer to take CT images of the colon and reconstruct a three-dimensional model of your colon. The inside of this model can be inspected, without causing any pain to you, to search for abnormalities. The test involves enlargement or distension of the colon with air. Early results show promise for screening the colon and detecting small polyps or asymptomatic colorectal cancers.
The main disadvantage of virtual colonoscopy is that any abnormalities have to be evaluated and treated by real-time colonoscopy. However, it is likely to have a place in screening for colorectal cancer.