Virtual Colonoscopy is a new method that permits doctors to look at the bowel (colon) to detect polyps and cancers. Polyps are small abnormal growths in the colon that can become cancerous if they are not removed. Virtual Colonoscopy is a recently developed method that uses a CT scanner and computer virtual reality software to examine inside the body without having to insert a long tube (Conventional Colonoscopy) into the colon or without having to fill the colon with liquid barium (Barium Enema).
Procedure
While preparations for virtual colonoscopy, the patient will usually be asked to take laxatives or other oral agents at home the day before the procedure to clear the colon.
VC is done in the radiology department of medical center. The examination takes place within 10 minutes and does not require sedatives. During the procedure,
- The patient is placed in a supine position on the table
- A thin tube is inserted into the rectum, so that air can be pumped through the tube in order to inflate the colon for better vision.
- The table moves into the scanner to produce a series of two-dimensional cross-sections along the length of the colon. A computer puts these images together to create a three-dimensional picture that can be viewed on the screen.
- The patient is told to hold his/her breath during the scan to avoid distortion on the images.
- The scan is then repeated with the patient in a prone position.
After the examination, the images produced by the scanner must be converted into a 3D image. A radiologist sorts the results to identify any disorder.
The patient may get back to normal activity after the procedure, but if abnormalities are found and the patient needs conventional colonoscopy.
Advantages
VC is comfortable than conventional colonoscopy for some patients because there is no use of a colonoscope. Consequently, no sedation is needed, and the patient can return to his/her usual activities or go home after the procedure without any aid. VC provides more detailed images than an x-ray using a barium enema, sometimes called a lower gastrointestinal (GI) series. Also it takes less time than either a conventional colonoscopy.
The main disadvantage to VC is cost. Another disadvantage is that a radiologist cannot take tissue samples or remove polyps during this process, so a conventional colonoscopy must be performed if lesions are found. In addition, VC does not show as much detail as a conventional colonoscopy, so cancerous cells smaller than 2 millimeters in diameter may not show up on the images. Virtual Colonoscopy done with CT exposes the patient to ionizing radiation; however some research has demonstrated that low dose VC can also be as effective in demonstrating colon and bowel disease due to the great difference in x-ray absorption between air and the tissue making the inner wall of the colon.
- People who should be screened for colorectal cancer
Currently, it's suggested that people of 50 years and older should be screened for colorectal cancer. If there's a tendency towards colon cancer in the family, it's advised to start 10 years earlier than 50 and to use a more sensitive and specific technique. But for the general population, this limit is 50 years and older.
- People over the age of 50 who get screened by this processes
The unfortunate thing is colorectal cancer should largely be a preventable illness, but in the United States at this time only 30 to 40 percent of people who ought to be screened have actually been screened. That gives us a lot of foundations to make up.
- Available screening methods for detection of colon cancer
While there is always new for technological improvements, we need to improve the current screening technologies. Despite their drawbacks, they have been proven effective in reducing the burden of disease. There are five regimens that are currently suggested, providing practitioners and patients with a menu of options. They include annual fecal occult blood testing (FOBT) - that is, looking for blood in the stool; sigmoidoscopy every five years; colonoscopy every 10 years; air-contrast barium enema every five years; and a combination of FOBT with flexible sigmoidoscopy, each at their usual intervals.
Each of these tests have various advantages and disadvantages; for instance, they differ in sensitivity and specificity -- that is, how well they detect colon cancer or polyps when they're present and reassure us when they're absent. Colon cancer is the end-result of a prolonged process during which changes in genes in the cells lining the intestine accumulate, resulting in abnormal growth of cells. If polyps gather additional genetic changes, a part of them may become cancerous. We are worry about polyps becoming cancerous as they grow; for instance, polyps greater than one centimeter in diameter are usually removed because they present a high cancer risk.
- Reasons that prevent people to be screened
There are many reasons why people aren't screened. Many people don’t recognize whether they should be screened or not. Do they know the current screening guidelines? If not, has colorectal cancer screening been recommended to them by their health care centers? Unfortunately, some recent surveys suggest that colorectal cancer screening is not usually recommended by health care centers, despite evidence of its benefit. Luckily, colon cancer screening and colonoscopy is now paid by Medicare, so cost is not as big a deal as it has been in the past.
- Optical colonoscopy considered the "gold standard" for colorectal cancer screening
Colonoscopy is taken as the gold standard for colorectal cancer screening by some groups but not by others. Some radiologists recommend colonoscopy as a preferred approach to colorectal screening. However, optical colonoscopy is considered the gold standard by some professionals because it permits complete visualization of the entire colon, hence providing the opportunity to identify precancerous polyps and cancer, and then to do diagnostic biopsies or therapeutic removal of these lesions, as soon as possible.
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