Virtual colonoscopy 1492174 224861569 2008-07-10T19:10:48Z Axl 128897 Reference '''Virtual colonoscopy''' (VC) is a [[medical imaging]] procedure which uses [[x-ray]]s and [[computer]]s to produce two- and [[3D computer graphics|three-dimensional]] images of the [[colon (anatomy)|colon]] (large intestine) from the lowest part, the [[rectum]], all the way to the lower end of the [[small intestine]] and display them on a screen.<ref name="Heiken">{{cite journal | last=Heiken | first=JP | coauthors=Peterson CM, Menias CO | title=Virtual colonoscopy for colorectal cancer screening: current status | journal=Cancer Imaging | volume=5 | issue=Spec No A | pages=S133–S139 | publisher=International Cancer Imaging Society | date=November 2005 | url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=16361129 | accessdate=2008-07-10 | pmid=16361129 | doi=10.1102/1470-7330.2005.0108 }}</ref> The procedure is used to [[diagnosis|diagnose]] colon and bowel disease, including [[polyp (medicine)|polyps]], [[diverticulosis]] and [[cancer]]. VC is performed via [[computed tomography]] (CT), sometimes called a CAT scan, or with magnetic resonance imaging ([[MRI]]).{{Fact|date=March 2008}} Not to be confused with a similar procedure called a [[CT Pneumocolon]], a virtual colonscopy can provide 3D reconstructed endoluminal views of the bowel. ==Procedure== While preparations for VC vary, the patient will usually be asked to take [[laxative]]s or other oral agents at home the day before the procedure to clear [[feces|stool]] from the colon. A [[suppository]] is also used to cleanse the rectum of any remaining fecal matter. The patient is also given a solution designed to coat any residual faeces which may not have been cleared by the laxative. This is called 'faecal tagging'. This allows the user (usually a [[Radiologist|consultant radiologist]]), viewing the 3D images to effectively subtract the left over faeces, which may otherwise give false positive results. VC takes place in the [[radiology]] department of a [[hospital]] or medical center. The examination takes about 10 minutes and does not require [[sedatives]]. During the procedure, * The patient is placed in a [[supine position]] on the examination 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 viewing. * The table moves through the scanner to produce a series of two-dimensional cross-sections along the length of the colon. A [[computer program]] puts these images together to create a three-dimensional picture that can be viewed on the [[video screen]]. * The patient is asked to hold his/her breath during the scan to avoid distortion on the images. * The scan is then repeated with the patient lying in a [[prone position]]. After the examination, the images produced by the scanner must be processed into a 3D image, +/- a fly through (a cine program which allows the user move through the bowel as if performing a normal colonoscopy). A radiologist evaluates the results to identify any abnormalities. The patient may resume normal activity after the procedure, but if abnormalities are found and the patient needs conventional [[colonoscopy]], it may be performed the same day.<ref>[http://digestive.niddk.nih.gov/ddiseases/pubs/virtualcolonoscopy/ Virtual Colonoscopy<!-- Bot generated title -->]</ref> ==Advantages== VC is more comfortable than conventional colonoscopy for some people because it does not use a colonoscope. As a result, no sedation is needed, and the patient can return to his/her usual activities or go home after the procedure without the aid of another person. VC provides clearer, more detailed images than a conventional x-ray using a [[barium enema]], sometimes called a lower gastrointestinal (GI) series. It also takes less time than either a conventional colonoscopy or a lower GI series.<ref>[http://ap.google.com/article/ALeqM5jaL3sgNRNQd2MBSVdY7ytcBpm4bwD8S207702]{{Dead link|date=March 2008}}</ref> ==Disadvantages== According to an [http://digestive.niddk.nih.gov/ddiseases/pubs/virtualcolonoscopy/index.htm article] on niddk.nih.gov, the main disadvantage to VC is cost. Another disadvantage is that a radiologist cannot take tissue samples ([[biopsy]]) or remove polyps during VC, so a conventional colonoscopy must be performed if abnormalities are 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 show up on the images.<ref>[http://www.eurekalert.org/pub_releases/2006-10/wfub-cc102406.php Findings presented at the American College of Gastroenterology] annual scientific meeting in Las Vegas, Nev. An abstract of the study was printed in the September 2006 issue of The American Journal of Gastroenterology.</ref> Furthermore Virtual Colonoscopy performed with CT exposes the patient to ionizing radiation, however some research has demonstrated that ultra-low dose VC can be just as effective in demonstrating colon and bowel disease due to the great difference in x-ray absorption between air and the tissue comprising the inner wall of the colon. Optical colonoscopy is taken as the "gold standard" for colorectal cancer screening by some groups but not by others. Some radiologists recommend VC 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. ==External links== * [http://radiologyinfo.org/en/info.cfm?PG=ct_colo RadiologyInfo] - The radiology information resource for patients * [http://www.acg.gi.org American College of Gastroenterology] (ACG) * [http://www.iffgd.org International Foundation for Functional Gastrointestinal Disorders] (IFFGD) * [http://www.lifesyne.com/colon.asp 3D Virtual colonoscopy flythrough from Lifesyne] * [http://www.viatronix.com/virtual-colonoscopy/ Virtual colonoscopy information and articles from Viatronix] * [http://mecca.louisville.edu/~msabry/projects/flyover.htm Fly-Over, A New Visualization for Colonoscopy] * [http://mecca.louisville.edu/~msabry/projects/cskel.htm Virtual Camera Path Planning for Colonoscopy] ==Source== * Adapted from public domain [http://digestive.niddk.nih.gov/ddiseases/pubs/virtualcolonoscopy/index.htm Virtual Colonoscopy]. National Digestive Diseases Information Clearinghouse. ==References== {{reflist}} [[Category:Medical tests]] [[Category:Diagnostic gastroenterology]] [[Category:Medical imaging]] [[yi:ווירטועל קאלאנסקאפי]]