CT colonography
From Ganfyd
A technique that uses computed tomography (CT) to image the colon. It is also known as CT colography, CT pneumocolon and is one technique for virtual colonoscopy (the latter can also be achieved by magnetic resonance imaging).
Following bowel preparation, air is insufflated into the bowel (pneumocolon) and spiral CT is used to collect the images [1]. The images are re-processed to construct a virtual image of how the bowel would look like if viewed from within the lumen of the bowel. The amount of radiation is equivalent to approximately two plain abdominal radiographs, i.e. less than that of a conventional abdominal CT.
It provides different information from conventional fibre-optic endoscopic colonoscopy, but can be useful for detecting colonic tumours. However, any abnormality detected would still require fibre-optic colonoscopy to confirm the lesion and take biopsies.
However, research into oral contrast agents may do away the with the need for bowel preparation and may make CT colonography a suitable imaging modality for colorectal cancer screening.
Sensitivity and Specificity
Some US studies indicate CT colonography can have a equal or superior sensitivity to conventional colonoscopy,[2][3] but this result has not been borne out in other studies.[4][5]
As with all investigations, reported accuracy rates will depend on the study population selected, equipment, computer software and operator factors. Meta-analysis [6][7] has recently re-inforced this and similar issues apply with MR colonography [8], which is another form of virtual colonoscopy.
References
- ↑ Halligan S, Fenlon HM. Virtual colonoscopy. BMJ. 1999 Nov 6;319(7219):1249-52.. Direct link: http://bmj.bmjjournals.com/cgi/content/full/319/7219/1249#B1
- ↑ Pickhardt PJ, Choi JR, Hwang I, Butler JA, Puckett ML, Hildebrandt HA, Wong RK, Nugent PA, Mysliwiec PA, Schindler WR. Computed tomographic virtual colonoscopy to screen for colorectal neoplasia in asymptomatic adults. N Engl J Med. 2003 Dec 4;349(23):2191-200.
- ↑ ERROR: No title found.
- ↑ Johnson CD, Harmsen WS, Wilson LA, Maccarty RL, Welch TJ, Ilstrup DM, Ahlquist DA. Prospective blinded evaluation of computed tomographic colonography for screen detection of colorectal polyps. Gastroenterology. 2003;125(2):311-9.
- ↑ Cotton PB, Durkalski VL, Pineau BC, Palesch YY, Mauldin PD, Hoffman B, Vining DJ, Small WC, Affronti J, Rex D, Kopecky KK, Ackerman S, Burdick JS, Brewington C, Turner MA, Zfass A, Wright AR, Iyer RB, Lynch P, Sivak MV, Butler H. Computed tomographic colonography (virtual colonoscopy): a multicenter comparison with standard colonoscopy for detection of colorectal neoplasia. JAMA. 2004 Apr 14;291(14):1713-9.
- ↑ Mulhall BP, Veerappan GR, Jackson JL. Meta-analysis: computed tomographic colonography. Ann Intern Med. 2005;142(8):635-50.
- ↑ Rosman AS, Korsten MA. Meta-analysis comparing CT colonography, air contrast barium enema, and colonoscopy. The American journal of medicine 2007;120(3):203-210.e4. (Direct link – subscription may be required.)
- ↑ Purkayastha S, Tekkis PP, Athanasiou T, Aziz O, Negus R, Gedroyc W, Darzi AW. Magnetic resonance colonography versus colonoscopy as a diagnostic investigation for colorectal cancer: a meta-analysis. Clin Radiol. 2005 Sep;60(9):980-9.
