Colon Cancer Screening CT
Colon cancer is a disease that affects the large bowel, also known as the colon, a part of the digestive system. Colon cancer is the second leading cause of cancer death in the United States. It is widely accepted that virtually all cases of colon cancer begin as small growths on the wall of the large bowel, called polyps. Polyps may contain malignant cancer cells. Over the course of several years, cancerous polyps may grow in size and invade the wall of the large bowel, forming a tumor. Once the tumor invades the wall of the colon it can shed cells into blood or lymphatic vessels. These cells can be carried to other parts of the body in the blood stream or lymph system, and new tumors may begin to grow elsewhere. This movement of cancer cells is called “metastasis.” By the time a new tumor is present in another location, the cancer is generally in an advanced stage and usually cannot be cured by surgery alone. Persons undergoing Colon Cancer Screening CT receive minimal exposure to low-dose radiation.
Am I a candidate for the CT Colon Cancer Screening Program?
One of the greatest advantages of Colon Cancer Screening CT is early disease detection in those who are well but possibly at risk for certain cancers. Colon cancer is more common in people over the age of fifty. Men are slightly more likely to develop colon cancer than women, but there is not enough difference in the rate of occurrence for there to be any difference in the recommendation for screening for men or women. The major policy setting bodies in colon cancer recommend that all people over the age of 50 be screened regularly for colon cancer. People younger than 50 who have close relatives with colon cancer (parents or siblings) are at higher risk for developing colon cancer and are also candidates for colon cancer screening.
What are the relative advantages of conventional colonoscopy and virtual colonoscopy?The most common means of screening for colon cancer is conventional colonoscopy, which involves threading a fiberoptic scope into the large bowel. This procedure is typically performed under sedation, requiring a recovery period. The bowel lining is directly visualized with a tiny optical camera. If polyps are found, they can be removed at the time of the procedure. The procedure has been considered the “gold standard” for colon cancer screening for a number of years. It is highly accurate and quite safe. The patient must thoroughly cleanse their bowel prior to the examination. This is called a bowel “prep.” There is a low incidence of complications associated with colonoscopy, including perforation of the colon wall. This is a rare occurrence, but can have serious consequences when it occurs.
CT colonoscopy (virtual colonoscopy) is a new technique for inspecting the wall of the colon. It is still under investigation and is not yet considered to be a standard screening test. Early clinical studies indicate that it is an accurate and safe technique when used to detect colon cancer and polyps at an early stage of development. The “prep” for virtual colonoscopy is the same as for conventional colonoscopy. Virtual colonoscopy has the advantage of allowing your doctors to see the lining of the colon without inserting a fiberoptic scope into the large bowel. This eliminates any risks and complications associated with conventional colonoscopy. The examination is typically performed without the use of sedation, therefore, patients are able to resume their normal activity after the examination. Since there is no endoscope employed, polyps identified on virtual colonoscopy cannot be removed at the time of the examination and the patient will require a conventional colonoscopy for removal of any polyps identified on the virtual colonoscopy examination.
What is involved in the colon screening CT?Plan enough time for patient registration in the Pacific Campus lobby prior to proceeding to the radiology department. When you arrive for your test you be asked to complete a questionnaire. Once completed, a radiologic technologist will escort you into the scanning room. You will be positioned on the CT scanner table and a short tube will be gently inserted into your rectum through and your large bowel will be inflated.
A high-speed scanner, Multidetector CT, is used to capture multiple images of the colon. Two scans are performed, one with you lying on your back and a second with you lying on your stomach. Each of these scans takes less than one minute. The majority of the examination time (18 minutes) is spent in scan preparation and positioning.
Once the scan has been completed the rectal tube is removed and you will naturally pass the carbon dioxide gas placed in the large bowel during the examination. You can resume your normal activities immediately after the scan. The images acquired during the exam are sent to a sophisticated computer workstation where they are processed and reviewed by an experienced radiologist.