Virtual colonoscopy (VC, also called CT Colonography or CT Pneumocolon) is a medical imaging procedure which uses x-rays and computers to produce two- and three-dimensional images of the 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.[1] The procedure is used to diagnose colon and bowel disease, including polyps, diverticulosis and cancer. VC is performed via computed tomography (CT), sometimes called a CAT scan, or with magnetic resonance imaging (MRI).[2] A virtual colonoscopy can provide 3D reconstructed endoluminal views of the bowel.
Contents
1Procedure
2Advantages
3Disadvantages
4External links
5Source
6References
Procedure
This video shows a virtual colonoscopy of the rectosigmoid colon performed in a retrograde fashion. There is a 10-mm colonoscopically-proven polyp in the sigmoid colon seen at the top of the frame at the midpoint of the movie. The movie concludes at the tip of the rectal tube which was used to insufflate the colon.
While preparations for VC vary, the patient will usually be asked to take laxatives or other oral agents at home the day before the procedure to clear stool from the colon. A suppository is also used to cleanse the rectum of any remaining fecal matter. The patient may 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 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
The patient may be given a dosage of Butylscopolamine intravenously to minimize muscle activity in the area.
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.[3]
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. The lack of sedation also lowers the risk of the procedure since some people may have adverse reactions to sedative medications used during conventional colonoscopy. VC provides clearer, more detailed images than a conventional x-ray using a barium enema, sometimes called a lower gastrointestinal (GI) series. Further, about 1 in 10 patients will not have a complete right colon (cecum) evaluation completed with conventional colonoscopy.[4] It also takes less time than either a conventional colonoscopy or a lower GI series.[5]
VC provides a secondary benefit of revealing diseases or abnormalities outside the colon.[6]
Disadvantages
According to an article on niddk.nih.gov, the main disadvantage to VC 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.[7] 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 the vast majority of the medical and research communities. Some radiologists recommend VC as a preferred approach to colorectal screening. However, virtual 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
RadiologyInfo - The radiology information resource for patients
American College of Gastroenterology (ACG)
International Foundation for Functional Gastrointestinal Disorders (IFFGD)
Virtual colonoscopy information and articles from Viatronix
Source
Adapted from public domain Virtual Colonoscopy. National Digestive Diseases Information Clearinghouse.
References
^Heiken, JP; Peterson CM, Menias CO (November 2005). "Virtual colonoscopy for colorectal cancer screening: current status: Wednesday 5 October 2005, 14:00–16:00". Cancer Imaging (International Cancer Imaging Society) 5 (Spec No A): S133–S139. doi:10.1102/1470-7330.2005.0108. PMC 1665314. PMID 16361129. //www.ncbi.nlm.nih.gov/pmc/articles/PMC1665314/.
^Bielen DJ, Bosmans HT, De Wever LL et al. (September 2005). "Clinical validation of high-resolution fast spin-echo MR colonography after colon distention with air". J Magn Reson Imaging22 (3): 400–5. doi:10.1002/jmri.20397. PMID 16106357.
^"Virtual Colonoscopy" - National Digestive Diseases Information Clearinghouse - NIH
^Menardo G (December 2004). "Sensitivity of diagnostic examinations for colorectal polyps". Tech Coloproctol8 Suppl 2: s273–5. doi:10.1007/s10151-004-0175-0. PMID 15666105.
^Virtual Colonoscopy - Mayo Clinic. "Virtual colonoscopy is typically faster than traditional colonoscopy. A scan of your colon takes about 10 minutes. Expect the entire virtual colonoscopy procedure to take 20 to 30 minutes."
^Yee J, Kumar NN, Godara S et al. (August 2005). "Extracolonic abnormalities discovered incidentally at CT colonography in a male population". Radiology236 (2): 519–26. doi:10.1148/radiol.2362040166. PMID 16040909. http://radiology.rsnajnls.org/cgi/pmidlookup?view=long&pmid=16040909. Retrieved 2008-12-22.
^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.
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Digestive system surgical and other procedures / Digestive system surgery (ICD-9-CM V3 42–54, ICD-10-PCS 0D)
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Medical testing : Medical imaging · Radiology · (ICD-9-CM V3 87–88, ICD-10-PCS B, CPT 70010–79999)
Comparison of the accuracy of CT colonography and colonoscopy in the diagnosis of colorectal cancer.
Martín-López JE1, Beltrán-Calvo C, Rodríguez-López R, Molina-López T.Author information 1Andalusian Health Technology Assessment (AETSA), Seville, Spain.AbstractAIM: The available evidence was reviewed to compare the effectiveness of CT colonography with that of colonoscopy for colorectal cancer (CRC) screening.
Colorectal disease : the official journal of the Association of Coloproctology of Great Britain and Ireland.Colorectal Dis.2014 Mar;16(3):O82-9. doi: 10.1111/codi.12506.
AIM: The available evidence was reviewed to compare the effectiveness of CT colonography with that of colonoscopy for colorectal cancer (CRC) screening.METHOD: An electronic search was conducted using PubMed, EMBASE, the Cochrane Library and Centre for Reviews and Dissemination databases, from incep
CT colonography: does it satisfy the necessary criteria for a colorectal screening test?
Pickhardt PJ.Author information Department of Radiology, University of Wisconsin School of Medicine & Public Health, E3/311 Clinical Science Center, 600 Highland Ave., Madison, WI, USA.AbstractExisting and emerging colorectal screening tests can be assessed in terms of the key categories of diagnostic performance, procedural risks, patient acceptability, and cost-effectiveness. To push a new screening test to acceptance, it need not outperform existing strategies in all of these criteria. Rather, a relative advantage in one criterion combined with acceptable performance in the others may be considered adequate. For computed tomographic colonography (CTC), a strong case can be made that this test meets or exceeds optical colonoscopy, the current screening standard, in all of these categories. Published data, including our own experience with CTC screening, will be reviewed to support this claim. Reasons why CTC has not yet achieved its full potential as a valuable screening test for colorectal cancer prevention will also be considered.
Expert review of gastroenterology & hepatology.Expert Rev Gastroenterol Hepatol.2014 Mar;8(3):211-3. doi: 10.1586/17474124.2014.887436. Epub 2014 Feb 4.
Existing and emerging colorectal screening tests can be assessed in terms of the key categories of diagnostic performance, procedural risks, patient acceptability, and cost-effectiveness. To push a new screening test to acceptance, it need not outperform existing strategies in all of these criteria.
Computer-aided detection for computed tomographic colonography screening: a prospective comparison of a double-reading paradigm with first-reader computer-aided detection against second-reader computer-aided detection.
Iussich G1, Correale L, Senore C, Hassan C, Segnan N, Campanella D, Bert A, Galatola G, Laudi C, Regge D.Author information 1From the *Radiology Unit, Institute for Cancer Research and Treatment, Candiolo; †im3D S.p.A., Torino; ‡AOU S Giovanni Battista, Torino; §Gastroenterology and Endoscopy Unit, Nuovo Regina Margherita Hospital, Rome; and ∥Gastroenterology and Endoscopy Unit, Institute for Cancer Research and Treatment, Candiolo, Italy.AbstractOBJECTIVES: The objective of this study was to prospectively compare diagnostic performance and time efficiency of a double-reading paradigm in which a first-reader computer-aided detection (CAD) is followed by a fast 2-dimensional review (DR FR-CAD) with those of a double reading with second-reader CAD (SR CAD).
OBJECTIVES: The objective of this study was to prospectively compare diagnostic performance and time efficiency of a double-reading paradigm in which a first-reader computer-aided detection (CAD) is followed by a fast 2-dimensional review (DR FR-CAD) with those of a double reading with second-reader
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