Virtual colonoscopy

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Virtual colonoscopy (VC, also called CT Colonography or CT Pneumocolon) is a medical imaging procedure that uses x-rays and computers to produce two- and three-dimensional images of the colon large) from the lowest part, rectum, to the lower end of the small intestine and display on the screen. This procedure is used to diagnose diseases of the colon and intestines, including polyps, diverticulosis and cancer. VC is done through computed tomography (CT), sometimes called CAT scan, or with magnetic resonance imaging (MRI). A virtual colonoscopy can provide a 3D endoluminal image of the reconstructed gut.

Video Virtual colonoscopy

Procedures

While preparation for VC varies, patients will usually be required to take laxatives or other oral agents at home the day before a procedure to clean stools from the colon. Suppositories are also used to clean the rectum from residual impurities. Patients can also be given solutions designed to coat residual debris that may have not been cleaned by a laxative, called 'faecal marking'. This allows the user (usually a radiologist consultant), looking at 3D images to effectively reduce the faeces of the remains, which may give false positive results.

The VC takes place in the radiology department of a hospital or medical center. The examination takes about 10 minutes and does not require tranquilizers.

During the procedure:

• The patient is placed in a supine position on the examination table
• Patients may be given intravenous doses of Butylscopolamine to minimize muscle activity in the area.
• Thin tubes are inserted into the rectum, allowing air to be pumped through the tubes to inflame the colon for a better view.
• The table moves through the scanner to produce a series of two-dimensional cross-sections along the length of the colon. The computer program puts these images together to create three-dimensional images that can be viewed on the video screen.
• The patient is asked to hold his breath during the scan to avoid distortion in the image.
• The scan is then repeated with the patient lying in prone position.

Upon inspection, the image produced by the scanner must be processed into 3D images,/- flies through (a cine program that allows the user to move through the gut as if doing a normal colonoscopy). A radiologist evaluates the results to identify any abnormality.

Patients can resume normal activity after the procedure, but if abnormalities are found and the patient requires a conventional colonoscopy, it may be done on the same day.

Maps Virtual colonoscopy

Benefits

VC is more comfortable than conventional colonoscopy for some people because it does not use colonoscope. As a result, no sedation is necessary, and the patient may return to his usual activities or go home after the procedure without the help of others. Lack of sedation also lowers the risk of the procedure as some people may have adverse reactions to the tranquilizers used during conventional colonoscopy. VC provides clearer and more detailed images than conventional x-rays using barium enema, sometimes called the lower gastrointestinal (GI) series. Furthermore, about 1 in 10 patients will not have a complete right colon evaluation complete with a conventional colonoscopy. It also takes less time than conventional colonoscopy or lower GI series.

VC provides additional benefits to reveal diseases or abnormalities outside the colon.

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Disadvantages

According to an article on niddk.nih.gov, the main disadvantage of VC is that a radiologist can not take a tissue sample (biopsy) or remove polyps during VC, so a conventional colonoscopy should be performed if an abnormality is found. Also, VC does not show as much detail as a conventional colonoscopy, so polyps smaller than between 2 and 10 millimeters in diameter may not appear in the image. Furthermore, a virtual colonoscopy performed by CT exposes the patient to ionizing radiation, on the order of miligray. Several studies have shown that low-dose VCs can be as effective as demonstrating bowel disease because of the large differences in x-ray absorption between air and tissue comprising the inner wall of the colon.

Optic colonoscopy is taken as the "gold standard" for colorectal cancer screening by most of the medical and research communities. However, some radiologists recommend VC as the preferred approach to colorectal screening. Virtual colonoscopy is favored by some professionals as it allows complete visualization of the entire colon, thereby providing more opportunities to identify polyps and pre-cancerous cancers, and to then perform rapid diagnostic biopsies or therapeutic removal of these lesions.

MRI (MRC) colonization allows similar visualizations without radiation exposure. Can detect larger adenomas and neoplasia with high specificity, but less sensitivity than conventional colonoscopy.

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Note

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References

• Adapted from the public domain of Virtual Colonoscopy. National Digestive Diseases Information Clearinghouse.

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External links

• RadiologyInfo - Radiology information source for patients
• American College of Gastroenterology (ACG)
• International Foundation for Functional Gastrointestinal Disorder (IFFGD)
• Virtual colonoscopy information and articles from Viatronix

Source of the article : Wikipedia