Virtual Endoscopy - Comparison with Colonoscopy in the Detection of Space-Occupying Lesions of the Colon

Background and Study Aims: A new technique has been described which combines abdominal helical computed tomography (CT) scanning and virtual reality computer technology, known as virtual colonoscopy (VC); the reconstructed images provide a simulation of the interior of the colon as viewed by endoscopy. We compared VC with conventional colonoscopy in patients with suspected or known colonic neoplasia.

Patients and Methods: A total of 38 patients, in whom there was a high likelihood of colonic polyps or cancer, underwent a noncontrast helical CT scan of the abdomen and pelvis after regular colonoscopy bowel preparation.The images were reconstructed into a VC presentation and compared with the subsequent conventional colonoscopy in a blinded manner.

Results: Conventional colonoscopy identified a total of 24 polyps 5 mm or greater. VC correctly identified five of 13 polyps 5 - 9 mm in size, and ten of 11 lesions greater than or equal to 10 mm in diameter. The reasons for four missed lesions were identified as being secondary to a collapsed rectum in two patients and stool in the right colon in two patients. The sensitivity and specificity per patient of VC for lesions greater than or equal to 5 mm were 66.7 % and 75.0 % respectively, and for lesions greater than 1 cm were 90.0 % and 82.1 %, respectively.

Conclusions: Virtual colonoscopy is feasible, well tolerated, and capable of detecting most lesions greater than 10 mm in diameter. This technique is continuing to be developed and warrants further evaluation as a diagnostic and screening tool in colorectal neoplasia.

References

• 1 Wingo P A, Tong T, Bolden B. Cancer Statistics, 1995.  Cancer Journal Clinics. 1995;  45 8-13
• 2 Stryker S J, Wolff B G, Culp C E, et al. Natural history of untreated colonic polyps.  Gastroenterology. 1987;  93 1009-1013
• 3 Hardcastle J D, Thomas W M, Chamberlain J, et al. Randomized controlled trial of fecal occult blood screening for colorectal cancer: results for first 107 349 subjects.  Lancet. 1989;  111 60-64
• 4 Kewenter R J, Bjork S, Haglind E, et al. Screening and rescreening for colorectal cancer: a controlled trial of fecal occult blood testing in 27 700 subjects.  Cancer. 1988;  62 645-651
• 5 Day J J, Freeman A H, Coni N K, Dixon A K. Barium enema or computed tomography for the frail elderly patient?.  Clin Radiol. 1993;  48 48-51
• 6 Amin Z, Boulos P B, Lees W R. Technical report: spiral CT pneumocolon for suspected colonic neoplasms.  Clin Radiol. 1996;  51 56-61
• 7 Hara A K, Johnson C D, Reed J E, et al. Detection of colorectal polyps by computed tomographic colography: feasibility of a novel technique.  Gastroenterology. 1996;  110 284-290
• 8 Vining D J, Gelfand D W. Non-invasive colonoscopy using helical CT scanning, 3D reconstruction, and virtual reality. Presented at the Society of Gastrointestinal Radiologists' Annual Meeting.  Maui, HI; February 1994
• 9 Vining D J, Teigen L, Stelt S D. Virtual colonoscopy: a 60-second colon examination (abstract).  Radiology. 1995;  197 281
• 10 Fenlon H M, Ferruci J T. Virtual colonoscopy: what will the issues be?.  Am J Roentgenol. 1997;  169 453-458
• 11 Teigen E, Vining D J, McCorquodale D. Improving virtual colonoscopy with a fecal contrast agent. Presented at the Society of Gastrointestinal Radiologists' Annual Meeting.  Cancun, Mexico; March 1997
• 12 Royster A P, Fenlon H M, Clarke P D, et al. CT colonoscopy of colorectal neoplasms: two-dimensional and three-dimensional virtual-reality techniques with colonoscopic correlation.  Am J Roentgenol. 1997;  169 1237-1242
• 13 Ferruci J T. Screening for colon cancer: programs of the American College of Radiology.  Am J Roentgenol. 1993;  160 999-1003
• 14 Rex D K, Cutler C S, Lemmel G T, et al. Colonoscopic miss rates of adenomas determined by back-to-back colonoscopies.  Gastroenterology. 1997;  112 24-28
• 15 Morales T G, Sampliner R E, Garewal H S, et al. The difference in colon polyp size before and after removal.  Gastrointest Endosc. 1996;  43 (1) 25-28
• 16 Gopalswamy N, Shenoy V N, Choudrhry U, et al. Is in vivo measurement of polyps during colonoscopy accurate?.  Gastrointest Endosc. 1997;  46 (6) 497-502
• 17 Hara A K, Johnson C D, Reed J E, et al. Reducing data size and radiation dose for CT colonography.  Am J Roentgenol. 1997;  168 1181-1184
• 18 Vining D J. Virtual endoscopy: is it reality?.  Radiology. 1996;  200 30-31
• 19 Kay C L, Evangelou H A. A review of the technical and clinical aspects of virtual endoscopy.  Endoscopy. 1996;  28 768-775
• 20 American Cancer Society guidelines for screening and surveillance for early detection of colorectal cancer and polyps. Update 1997.  Cancer. 1997;  47 154-160
• 21 Hermanek P. Dysplasia-carcinoma sequence, types of adenomas and early colorectal carcinoma.  Eur J Surg Oncol. 1987;  13 141-143
• 22 Shinya H, Wolff W I. Morphology, anatomic distribution and cancer potential of colonic polyps.  Ann Surg. 1979;  190 679-683
• 23 Hofstad B, Vatn M H, Andersen I, et al. Growth of colorectal polyps: redetection and evaluation of unresected polyps for a period of three years.  Gut. 1996;  39 449-456
• 24 Kay C L, Aabakken L, Evangelou H, et al. Virtual colonoscopy - a pig model for optimization of study parameters (abstract).  Am J Gastroenterol. 1996;  91 349
• 25 Dachman A H, Lieberman J, Osnis R B, et al. Small simulated polyps in pig colon: sensitivity of CT virtual colography.  Radiology. 1997;  203 427-430
• 26 Luboldt W, Bauerfeind D P, Steiner P, Fried M, et al. Preliminary assessment of three dimensional magnetic resonance imaging for various colonic disorders.  Lancet. 1997;  349 1288-1291
• 27 Schoenenberger A W, Bauerfeind D P, Krestin G, Debatin G F. Virtual colonoscopy with magnetic resonance imaging: in vitro evaluation of a new concept.  Gastroenterology. 1997;  112 1863-1870
• 28 Springer P, Dessl A, Giacomuzzi S M, et al. Viral computed tomographic gastroscopy: a new technique.  Endoscopy. 1997;  29 632-634
• 29 Morrin M M, Kruskal J B, Farrell R J, et al. Endoluminal CT colonography after an incomplete endoscopic colonoscopy.  Am J Roentgenol. 1999;  172 913-918
• 30 Macari M, Berman P, Dicker M, et al. Usefulness of CT colonography in patients with incomplete colonoscopy.  Am J Roentgenol. 1999;  173 561-564