An analysis of the potential impact of computed tomographic colonography (virtual colonoscopy) on colonoscopy demand

BACKGROUND AND AIMS: There has been much speculation about the potential impact on the use of conventional colonoscopy if "virtual" computed tomographic colonography (CTC) became a widely accepted modality for colorectal cancer (CRC) screening. However, no formal analysis of the impact of CTC on colonoscopy demand has been reported. METHODS: A mathematical model to predict colonoscopy demand based on several relevant input parameters was constructed. Current national colonoscopy practice, estimated using various published reports, was used as the foundation to project colonoscopy demand if CTC were implemented as the primary CRC screening modality. RESULTS: In the base-case analysis, if CTC were used as the primary modality for CRC screening, 1.78 million colonoscopies could be eliminated from the total 6.47 million in 2003. Depending on the polyp size threshold used to define a CTC study as positive (6 or 10 mm), this loss would be partially offset by 1.21 million (6 mm) or .34 million (10 mm) follow-up colonoscopies for CTC examinations with positive findings, resulting in a net loss of .57 million (8.8% decrease) (6 mm) or 1.44 million (22.3% decrease) (10 mm). Extensive sensitivity analyses showed that the findings of this model were robust and insensitive to most parameters tested but were sensitive to a few parameters, including the percentage of CTC examinations with positive findings. CONCLUSIONS: Wide-scale implementation of CTC for CRC screening would likely lead to a decrease in use of conventional colonoscopy. The percentage of CTC studies with positive findings seemed to be a pivotal variable, which would be determined in large part by the polyp size ultimately established to define a positive finding.     

Computed tomographic virtual colonoscopy computer-aided polyp detection in a screening population

BACKGROUND & AIMS: The sensitivity of computed tomographic (CT) virtual colonoscopy (CT colonography) for detecting polyps varies widely in recently reported large clinical trials. Our objective was to determine whether a computer program is as sensitive as optical colonoscopy for the detection of adenomatous colonic polyps on CT virtual colonoscopy. METHODS: The data set was a cohort of 1186 screening patients at 3 medical centers. All patients underwent same-day virtual and optical colonoscopy. Our enhanced gold standard combined segmental unblinded optical colonoscopy and retrospective identification of precise polyp locations. The data were randomized into separate training (n = 394) and test (n = 792) sets for analysis by a computer-aided polyp detection (CAD) program. RESULTS: For the test set, per-polyp and per-patient sensitivities for CAD were both 89.3% (25/28; 95% confidence interval, 71.8%-97.7%) for detecting retrospectively identifiable adenomatous polyps at least 1 cm in size. The false-positive rate was 2.1 (95% confidence interval, 2.0-2.2) false polyps per patient. Both carcinomas were detected by CAD at a false-positive rate of 0.7 per patient; only 1 of 2 was detected by optical colonoscopy before segmental unblinding. At both 8-mm and 10-mm adenoma size thresholds, the per-patient sensitivities of CAD were not significantly different from those of optical colonoscopy before segmental unblinding. CONCLUSIONS: The per-patient sensitivity of CT virtual colonoscopy CAD in an asymptomatic screening population is comparable to that of optical colonoscopy for adenomas > or = 8 mm and is generalizable to new CT virtual colonoscopy data.     

Clinical significance of virtual colonoscopy (CT colonography) with special reference to polyp morphology

BACKGROUND/AIMS: Computed tomographic colonography [virtual colonoscopy (VC)] is a new imaging method that may contribute to the detection of colorectal neoplasms. The aim of this study was to investigate the clinical significance of VC for the diagnosis of colorectal tumors with special reference to their morphology. METHODOLOGY: Sixteen patients with colorectal tumors were enrolled in this study. Colonic preparation was performed using magnesium sulfate, and scopolamine butylbromide was injected before air insufflation from the anus. VC was performed with an Aquilion multislice CT system (Toshiba) and Workstation M900 maximum (ZIO). The results were compared with those of conventional colonoscopy (CC). In six cases, total colonoscopy was not possible due to tumor stricture. RESULTS: The number of lesions detected by CC was 58; 48 early carcinomas/adenomas (group A) and 10 advanced carcinomas (group B). All group B lesions and 43.8% (21 lesions) of group A lesions were identified by VC. The specificity of VC for group A and B lesions was 45.8% and 100%, respectively. There was no significant difference in detection rate for group A lesions by subclassification according to their morphology: pedunculated; 22% (2/9), semipedunculated; 50% (6/12), sessile; 29% (4/14), superficially elevated; 56% (5/9), and superficially elevated morphology with central depression; 100% (4/4). The mean diameter of the lesions that were detected and not detected by VC was 7+/-8.0 mm (range: 3-30 mm) and 8+/-5.8 mm (range: 2-20 mm), respectively (P=0.90). CONCLUSIONS: Polyps with superficial morphology could be detected by VC as well as those with protuberant morphology. According to evidence that neither the morphology nor the size of a lesion was a significant factor for detection by VC, the authors consider that the diagnostic ability of VC may be improved by better preparation.     

Comparison of multidetector computed tomographic colonography and conventional colonoscopy for detection of colorectal polyps and cancer.

BACKGROUND: Computed tomographic colonography (CTC) is a new technique for detecting colonic neoplasms. Data on the utility of this method in the Indian population are limited. METHODS: Forty-two patients with symptoms of colonic disease underwent CTC and conventional colonoscopy (CC) within one week of each other and the findings at these two investigations were compared. RESULTS: The entire colon could be evaluated in 38 patients on CTC and in 23 patients on CC. Of the 19 patients who had incomplete CC, 14 had occlusive colonic lesions. Of the 86 lesions detected on CC, 76 (88.4%) were correctly identified on CTC with regard to location and size. CTC was false negative for 10 lesions and false positive for 5 lesions in 3 patients. The sensitivity and specificity of CTC were 65% and 77%, respectively, for lesions 1-5 mm; 97% and 83% for 6-9 mm-sized lesions; and 100% and 100% for lesions 10 mm or larger. Extracolonic findings were seen in 24 of 42 patients (57%). CONCLUSIONS : CTC is reliable for detecting lesions 6 mm or larger in size. It permits evaluation of the region proximal to an occlusive growth, which is often not possible with CC.     

Community-based screening by colonoscopy or computed tomographic colonography in asymptomatic average-risk subjects

OBJECTIVES: Visualizing the entire colorectum in screening is an advantage of colonoscopy, and also computed tomographic (CT) colonography, another potentially suitable screening test. Our objective was to compare screening CT colonography and colonoscopy in an asymptomatic average-risk population, and to determine whether providing a choice of tests increased participation. METHODS: One thousand and four hundred subjects from the general community, randomly selected from the parliamentary electoral roll, were allocated one of three screening groups: colonoscopy, CT colonography, or a choice of these tests, and were sent an institutional letter of invitation. Those with symptoms, colorectal cancer in first-degree relatives, or colonoscopy within 5 yr were ineligible. Outcome measures were participation, acceptability of screening, and yield for advanced colorectal neoplasia in participants. RESULTS: Of the subjects, 24.9% were ineligible; the overall participation rate was 18.2% (184/1,009). Participation in each screening group was not different. Both tests were accompanied by the same high levels of acceptability; most participants found colonoscopy (87%) and CT colonography (67%, p < 0.001) less unpleasant than expected. About 29% (26/89) CT colonography subjects had a positive screening test. The yield of advanced colorectal neoplasia was 8.7% (95% CI 5-14%), with no difference in yield between tests. CONCLUSION: Colorectal neoplasia screening by colonoscopy or CT colonography was associated with modest participation, high levels of acceptability, and similar yield for advanced colorectal neoplasia. Providing a choice of test did not increase participation.     

Role of virtual computed tomographic colonography in patients with colorectal cancers and obstructing colorectal lesions

PURPOSE: The aim of this study was to assess the ability of computed tomographic colonography to diagnose colorectal masses, stage colorectal cancers, image the proximal colon in obstructing colorectal lesions, and evaluate the anastomoses in patients with previous colorectal surgery. METHODS: We prospectively performed computed tomographic colonography examinations in 34 patients (20 males; mean age, 64.2; range, 19–91 years): 20 patients had colorectal masses (defined at endoscopy as intraluminal masses 2 cm or larger), 7 patients had benign obstructing colorectal strictures, and 7 patients had a prior colorectal resection. Final tumor staging was available in all 16 patients who had colorectal cancers and 15 patients were referred after incomplete colonoscopy. The ability of computed tomographic colonography to stage colorectal cancers, identify synchronous lesions in patients with colorectal masses, and image the proximal colon in patients with obstructing colorectal lesions was assessed. RESULTS: Computed tomographic colonography identified all colorectal masses, but overcalled two masses in patients who were either poorly distended or poorly prepared. Computed tomographic colonography correctly staged 13 of 16 colorectal cancers (81 percent) and detected 16 of 17 (93 percent) synchronous polyps. Computed tomographic colonography overstaged two Dukes Stage A cancers and understaged one Dukes Stage C cancer. A total of 97 percent (87/90) of all colonic segments were adequately visualized at computed tomographic colonography in patients with obstructing colorectal lesions compared with 60 percent (26/42) of segments at barium enema (P<0.01). Colonic anastomoses were visualized in all nine patients, but in one patient, computed tomographic colonography could not distinguish between local tumor recurrence and surgical changes. CONCLUSION: Computed tomographic colonography can accurately identify all colorectal masses but may overcall stool as masses in poorly distended or poorly prepared colons. Computed tomographic colonography has an overall staging accuracy of 81 percent for colorectal cancer and is superior to barium enema in visualizing colonic segments proximal to obstructing colorectal lesions.Read at The American Society of Colon and Rectal Surgeons' 100th Anniversary and Tripartite Meeting, Washington D.C., May 1 to 6, 1999.     

Single-center study comparing computed tomography colonography with conventional colonoscopy

AIM： To compare the results from computed tomography （CT） colonography with conventional colonoscopy in symptomatic patients referred for colonoscopy. METHODS： The study included 227 adult outpatients, mean age 60 years, with appropriate indications for colonoscopy. CT colonography and colonoscopy were performed on the same day in a metropolitan teaching hospital. Colonoscopists were initially blinded to the results of CT colonography but there was segmental unblinding during the procedure. The primary outcome measures were the sensitivity and specificity of CT colonography for the identification of polyps seen at colonoscopy （i.e. analysis by polyp）. Secondary outcome measures included an analysis by patient, extracolonic findings at CT colonography, adverse events with both procedures and patient acceptance and preference. RESULTS： Twenty-five patients （11%） were excluded from the analysis because of incomplete colonoscopy or poor bowel preparation that affected either CT colonography, colonoscopy or both procedures. Polyps and masses （usually cancers） were detected at colonoscopy and CT colonography in 35% and 42% of patients, respectively. Of nine patients with a final diagnosis of cancer, eight （89%） were identified by CT colonography as masses （5） or polyps （3）. For polyps analyzed according to polyp, the overall sensitivity of CT colonography was 50% （95% CI, 39%-61%） but this increased to 71% （95% CI, 52%-85%） for polyps ≥ 6 mm in size. Similarly, specificity for all polyps was 48% （95% CI, 39%-58%） increasing to 67% （95% CI, 56%-76%） for polyps ≥6 mm. Adverse events were uncommon but included one colonic perforation at colonoscopy, Patient acceptance was high for both procedures but preference favoured CT colonography. CONCLUSION： Although CT colonography was more sensitive in this study than in some previous studies, the procedure is not yet sensitive enough for widespread application in symptomatic patients.     

Performance of multidetector computed tomography colonography compared with conventional colonoscopy

BACKGROUND AND AIMS: This was a prospective blinded study to compare computed tomography (CT) colonography, performed with multidetector arrays CT scan (MDCT), with conventional colonoscopy for the detection of colorectal neoplasia. METHODS: Fifty patients were examined by MDCT after standard bowel preparation and rectal air insufflation in the supine and prone positions. Data sets were examined by one radiologist and one gastroenterologist blinded to the patient's history and colonoscopy results. Patients subsequently underwent colonoscopy on the same day, which served as the gold standard. RESULTS: Nine of 11 lesions >10 mm (82%), 5/15 lesions of 6-9 mm (33%), and 1/42 polyps <5 mm (3%) were detected by MDCT colonography. One false positive result for a structure larger than 10 mm was described. Nineteen of 21 patients who had no lesions during conventional colonoscopy were considered free of lesions by MDCT colonography, yielding a per patient specificity of 90%. CONCLUSION: MDCT colonography provides good data quality and has good sensitivity and specificity for the detection of colonic lesions of 10 mm or more.     

Colorectal neoplasm detection using virtual colonoscopy: a feasibility study

Background—Virtual colonoscopy is a potentiallypowerful tool for non-invasive colorectal evaluation. In vitro studieshave established its accuracy in simulated polyp detection but little data exist regarding its use in clinical practice.
Aims—To evaluate the ability of virtualcolonoscopy to detect colorectal cancers and polyps in patients withendoscopically proven colorectal neoplasms and to correlate thefindings of virtual colonoscopy with those of conventional colonoscopy,surgery, and histopathology.
Patients—Thirty eight patients with endoscopicfindings suggestive of colorectal carcinoma.
Methods—Virtual colonoscopy was performed usingthin section helical computed tomography (CT) of the abdomen and pelvisafter rectal insufflation of room air. Commercially available software was used to generate endoscopic "fly through" examinations of thecolon from the CT data. Results were correlated with the findings ofconventional colonoscopy and with the surgical and histopathological outcome in each case.
Results—Thirty eight pathologically provencolorectal cancers and 23 adenomatous polyps were present. On virtualcolonoscopy, all cancers and all polyps measuring greater than 6 mm insize were identified; there were two false positive reports of polyps. On conventional colonoscopy, there was one false positive report of amalignant sigmoid stricture; four subcentimetre polyps were overlooked.Virtual colonoscopy enabled visualisation of the entire colon in 35 patients; conventional colonoscopy was incomplete in 14 patients.Virtual colonoscopy correctly localised all 38cancers, compared with32 using conventional colonoscopy.
Conclusion—Virtual colonoscopy is a feasiblemethod for evaluating the colon; it may have role in diagnosis ofcolorectal cancer and polyps.

Keywords:colonic neoplasms; computed tomography; computersimulation

     

Prospective blinded evaluation of computed tomographic colonography for screen detection of colorectal polyps

BACKGROUND & AIMS: This study used a low lesion prevalence population reflective of the screening setting to estimate the sensitivity and specificity of computerized tomographic (CT) colonography for detection of colorectal polyps. METHODS: This prospective, blinded study comprised 703 asymptomatic persons at higher-than-average risk for colorectal cancer who underwent CT colonography followed by same-day colonoscopy. Two of 3 experienced readers interpreted each CT colonography examination. RESULTS: Overall lesion prevalence for adenomas >/=1 cm in diameter was 5%. Seventy percent of all lesions were proximal to the descending colon. With colonoscopy serving as the gold standard, CT colonography detected 34%, 32%, 73%, and 63% of the 59 polyps >/=1 cm for readers 1, 2, 3, and double-reading, respectively; and 35%, 29%, 57%, and 54% of the 94 polyps 5-9 mm for readers 1, 2, 3, and double-reading, respectively. Specificity for CT colonography ranged from 95% to 98% and 86% to 95% for >1 cm and 5-9-mm polyps, respectively. Interobserver variability was high for CT colonography with kappa statistic values ranging from -0.67 to 0.89. CONCLUSIONS: In a low prevalence setting, polyp detection rates at CT colonography are well below those at colonoscopy. These rates are less than previous reports based largely on high lesion prevalence cohorts. High interobserver variability warrants further investigation but may be due to the low prevalence of polyps in this cohort and the high impact on total sensitivity of each missed polyp. Specificity, based on large numbers, is high and exhibits excellent agreement among observers.     

Evaluation of contrast-enhanced computed tomographic colonography in detection of local recurrent colorectal cancer

AIM:To evaluate the diagnostic accuracy,sensitivity,specificity of contrast-enhanced computed tomographiccolonography in detecting local recurrence of colorectalcancer.METHODS:From January 2000 to December 2004,434 patients after potentially curative resection for in-vasive colorectal cancer were followed up for a periodranging from 20 to 55 mo.Eighty of the four hundredand thirty-four patients showing strong clinical evidencefor recurring colorectal cancer during the last follow-up were enrolled in this study.Each patient underwentcontrast-enhanced computed tomographic colonographyand colonoscopy on the same day.Any lesions,biopsies,identified during the colonoscopic examination,imme-diate complications and the duration of the procedurewere recorded.The results of contrast-enhanced com-puted tomographic colonography were evaluated bycomparing to those of colonoscopy,surgical finding,andclinical follow-up.RESULTS:Contrast-enhanced computed tomographiccolonography had a sensitivity of 100%,a specificity of83% and an overall accuracy of 94% in detecting localrecurrent colorectal cancer.CONCLUSION:Conventional colonoscopy and contrast-enhanced tomographic colonography can complementeach other in detecting local recurrence of colorectalcancer.     

Extracolonic findings of computed tomographic colonography in Koreans

AIM： To determine the frequency and characteristics of extracolonic lesions detected using computed tomographic （CT） colonography.
METHODS： The significance of extracolonic lesions was classified as high, intermediate, or low. Medical records were reviewed to establish whether further investigations were carried out pertaining to the extracolonic lesions that were detected by CT colonography.
RESULTS： A total of 920 cases from 7 university hospitals were included, and 692 extracolonic findings were found in 532 （57.8%） patients. Of 692 extracolonic findings, 60 lesions （8.7%） were highly significant, 250 （36.1%） were of intermediate significance, and 382 （55.2%） were of low significance. CT colonography revealed fewer extracolonic findings in subjects who were without symptoms （P 〈 0.001）, younger （P 〈 0.001）, or who underwent CT colonography with no contrast enhancement （P = 0.005）. CT colonography with contrast enhancement showed higher cost-effectiveness in detecting highly significant extracolonic lesions in older subjects and in subjects with symptoms.
CONCLUSION： Most of the extracolonic findings detected using CT colonography were of less significant lesions. The role of CT colonography would be optimized if this procedure was performed with contrast enhancement in symptomatic older subjects.     

Diagnostic accuracy and interobserver agreement of CT colonography (virtual colonoscopy)

BACKGROUND AND AIMS: Computed tomographic (CT) colonography or virtual colonoscopy (VC) is a non-invasive imaging method proposed for screening patients with colorectal neoplasias. Our aims were to study the diagnostic accuracy and interobserver agreement of VC for correct patient identification compared with conventional colonoscopy (CC). METHODS: This was a prospective study of 50 patients successively undergoing VC and CC. Multiplanar two dimensional CT images and three dimensional VC were constructed using surface rendering software and interpreted by two independent investigator teams. VC findings were compared with those of CC. Interobserver agreement was determined using kappa statistics. RESULTS: CC found 65 polyps in 24 patients. For identification of patients with polyps > or =10 mm, the sensitivity of VC was 38% and 63%, and specificity was 74% and 74% for teams 1 and team 2. Interobserver agreement was good (kappa 0.72). For patients with polyps of any size, the sensitivity of VC was 75% and 71%, and specificity was 62% and 69% for teams 1 and 2. Interobserver agreement was fair (kappa 0.56). Accuracy improved when comparing the results of the first 24 with the last 26 patients. CONCLUSIONS: In our experience, VC had a low diagnostic value for identification of patients with colorectal neoplasias. Interobserver agreement for VC interpretation was fair. These results may be explained by software imperfections and a learning curve effect.