Other Tests You Might Be Given

Imaging tests are also used to screen for and detect colorectal cancer. These tests use technologies that visualize your bodily 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.

Imaging tests you may be given include:

• Virtual colonoscopy. 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, obviously without causing any pain to you, while searching 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 colonoscopy. However it is likely to have a place in screening for colorectal cancer.
• Magnetic resonance imaging. Commonly called MRI, this test produces very clear pictures, or images, of the human body without the use of X-rays. MRI uses a large magnet, radio waves and a computer to produce these images. The MRI examination poses no risk to the average person if appropriate safety guidelines are followed.
• Ultrasound. When ultrasound is performed high-frequency sound waves bounce back off the organs in the body and are caught by a receiver, which translates the sound into pictures. In this way the person doing the ultrasound can see your internal organs. Ultrasound may be used in colon cancer to determine if the cancer has spread.
• Angiography. This is a special type of test used to look at blood vessels. This test is done when the doctor suspects a blockage in or around a blood vessel, that a blood vessel may be bleeding or to visualize where the blood vessels are located. A blockage interferes with blood flow, which can result in belly pain or bleeding from the digestive tract. In the case of colorectal cancer, angiography can be used to exclude other diagnoses, or if the cancer has spread to the liver, it can show surgeons the location of blood vessels so that they can remove the tumor in the liver without causing a lot of bleeding.
• Radionuclide Scanning. Also called nuclear medicine scanning, this is a test that produces pictures of internal parts of the body using small amounts of radioactive material. This test is used to provide images of organs and areas of the body that cannot be seen well with standard X-rays. Many abnormal tissue growths or tumors are particularly visible using radionuclide scanning.In addition to showing the structure of an organ, radionuclide scanning allows the doctor to see how the organ is functioning. A diseased or poorly working organ will appear differently on the scan than will a healthy organ.