Sensitivity Of Computed Tomographic Colonography Research Articles

Review of computed tomographic colonography from a surgeon's perspective.

New research has addressed many of the early concerns of computed tomographic colonography (CTC) and these studies are now beginning to shape clinical practices. A review of the literature demonstrates that the sensitivity of CTC in screening for large polyps (>/= 1cm) or cancers in the large intestine is as high as that of conventional optical colonoscopy, however, the sensitivity decreases with the diameter of the polyp. Despite this, CTC is well tolerated, more acceptable to patients than optical colonoscopy and therefore may improve colorectal cancer screening compliance. This review not only describes the diagnostic accuracy and sensitivity of CTC, and the evolving role of CTC as a primary colon cancer screening option, but also the recent studies that have demonstrated the additional value of CTC utilization for practicing clinicians.

CT colonography in the diagnosis and management of colorectal cancer: Emphasis on pre- and post-surgical evaluation

This article addresses the use of computed tomographic colonography (CTC) for the diagnosis and management of colorectal cancer, focusing on presurgical evaluation of the colon proximal to an occlusive cancer and surveillance after cancer resection surgery. The key evidences accumulated in the literature and future work needed are summarized. CTC is a technically robust and the most practical method to evaluate the colon proximal to an occlusive cancer, which prevents colonoscopic examination past the occlusion, either before or after metallic stent placement. The high sensitivity of CTC for detecting cancers and advanced adenomas in the proximal colon can help prevent additional surgical procedures in patients showing negative results. However, the accuracy of CTC for distinguishing intramural cancers from adenomas is low, and the technique is limited in guiding management when a medium-sized lesion that do not show invasive features such as pericolic extension or nodal metastasis is found in the proximal colon. A maximal diameter ≥ 15 mm has been proposed as a criterion for surgical removal of proximal lesions. However, this needs to be verified in a larger cohort. In addition, the influence of presurgical CTC results on the current post-cancer resection colonic surveillance timeline remains to be determined. CTC can be readily added to the routine abdominopelvic CT in the form of contrast-enhanced CTC, which can serve as an effective stand-alone tool for post-cancer resection surveillance of both the colorectum and extracolonic organs. Although the accuracy of CTC has been demonstrated, its role in the current colonoscopy-based postoperative colonic surveillance protocols remains to be determined. Readers of CTC also need to be knowledgeable on the colonic lesions that are unique to the postoperative colon.

Efficacy of Computer-aided Detection as a Second Reader for 6–9-mm Lesions at CT Colonography: Multicenter Prospective Trial

To assess the effect of computer-aided detection (CAD) as a second reader on the sensitivity and specificity of computed tomographic (CT) colonography in detecting 6-9-mm colorectal cancer (CRC) lesions. Individuals with clinical indications for colonoscopy--either for symptoms or as part of participating in a surveillance program or CRC screening--were prospectively enrolled at one of 10 academic centers between July 2007 and May 2009. Institutional review board approval was obtained at each clinical site, and all participants provided written informed consent. All participants underwent CT colonography and colonoscopy on the same day. Experienced readers interpreted the CT colonography images unassisted and then reviewed all colorectal lesion-like structures pinpointed by the CAD algorithm. Segmental unblinding of CT colonoscopy findings at colonoscopy was utilized. The sensitivity and specificity of unassisted and CAD-assisted reading in identifying individuals with 6-9-mm lesions were calculated and compared by means of pairwise analysis. A total of 618 participants (mean age, 57.9 years; 54.5% male) were included in the final analysis. Of these participants, 464 (75.1%) had no lesions 6 mm or larger, and 52 (8.4%) had 6-9-mm lesions. The sensitivity of CT colonography with unassisted reading and that with CAD-assisted reading in identifying individuals with 6-9-mm lesions was 65.4% (95% confidence interval [CI]: 50.9%, 78.0%) and 76.9% (95% CI: 63.2%, 87.5%; P = .016), respectively. No significant change in specificity was observed: The specificity of CT colonography with unassisted and that with CAD-assisted reading was 91.8% (95% CI: 88.9%, 94.1%) and 90.9% (95% CI: 88.0%, 93.4%; P = .063), respectively. Evaluation of CAD candidates required an additional 1.6 minutes (25th-75th percentile: 1.0 minute to 3.4 minutes). The addition of CAD to reading performed by experienced readers resulted in a significant benefit in the detection of 6-9-mm polyps at CT colonography in this cohort. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120376/-/DC1.

Miss rate of colorectal cancer at CT colonography in average-risk symptomatic patients

Computed tomographic colonography (CTC) is a less burdensome alternative to colonoscopy in excluding colorectal cancer (CRC) in symptomatic patients. We evaluated the proportion of patients who underwent CTC in whom CRC was missed. Patients who had undergone CTC in the period 1 January 2007 to 1 January 2011 were merged with all cases of CRC recorded in the Cancer Registry between 1 January 2007 and 1 July 2011 to identify all patients who had undergone CTC less than 2 years before CRC had been diagnosed. In 53 out of 1,855 patients who had undergone CTC, CRC was diagnosed. Of these, 40 patients had suspected CRC and 5 had large polyps at CTC. In five patients with an indeterminate mass, further investigation confirmed malignancy. One cancer in the caecum was missed because of poor distension. Two cancers were missed: one in the distal rectum and one in the ascending colon. Sensitivity of CTC for CRC was 94.3 % (95 % CI 88-100 %). The true miss rate, excluding the inadequate distended study, was 2 out of 53 (3.8 %). This study shows that the miss rate for CTC is low, which means that CTC is accurate in excluding CRC in symptomatic patients at a relatively low risk of CRC.

Diagnostic Accuracy of Laxative-Free Computed Tomographic Colonography for Detection of Adenomatous Polyps in Asymptomatic Adults

Colon screening by optical colonoscopy (OC) or computed tomographic colonography (CTC) requires a laxative bowel preparation, which inhibits screening participation. To assess the performance of detecting adenomas 6 mm or larger and patient experience of laxative-free, computer-aided CTC. Prospective test comparison of laxative-free CTC and OC. The CTC included electronic cleansing and computer-aided detection. Optical colonoscopy examinations were initially blinded to CTC results, which were subsequently revealed during colonoscope withdrawal; this method permitted reexamination to resolve discrepant findings. Unblinded OC served as a reference standard. (ClinicalTrials.gov registration number: NCT01200303) Multicenter ambulatory imaging and endoscopy centers. 605 adults aged 50 to 85 years at average to moderate risk for colon cancer. Per-patient sensitivity and specificity of CTC and first-pass OC for detecting adenomas at thresholds of 10 mm or greater, 8 mm or greater, and 6 mm or greater; per-lesion sensitivity and survey data describing patient experience with preparations and examinations. For adenomas 10 mm or larger, per-patient sensitivity of CTC was 0.91 (95% CI, 0.71 to 0.99) and specificity was 0.85 (CI, 0.82 to 0.88); sensitivity of OC was 0.95 (CI, 0.77 to 1.00) and specificity was 0.89 (CI, 0.86 to 0.91). Sensitivity of CTC was 0.70 (CI, 0.53 to 0.83) for adenomas 8 mm or larger and 0.59 (CI, 0.47 to 0.70) for those 6 mm or larger; sensitivity of OC for adenomas 8 mm or larger was 0.88 (CI, 0.73 to 0.96) and 0.76 (CI, 0.64 to 0.85) for those 6 mm or larger. The specificity of OC at the threshold of 8 mm or larger was 0.91 and at 6 mm or larger was 0.94. Specificity for OC was greater than that for CTC, which was 0.86 at the threshold of 8 mm or larger and 0.88 at 6 mm or larger (P= 0.02). Reported participant experience for comfort and difficulty of examination preparation was better with CTC than OC. There were 3 CTC readers. The survey instrument was not independently validated. Computed tomographic colonography was accurate in detecting adenomas 10 mm or larger but less so for smaller lesions. Patient experience was better with laxative-free CTC. These results suggest a possible role for laxative-free CTC as an alternate screening method.

Computed tomographic colonography in the diagnosis of colorectal cancer

This study aimed to determine the sensitivity of computed tomographic colonography (CTC) in diagnosing colorectal cancer and to explore the reasons why these cancers are missed on CTC. Patients who underwent CTC in the 56-month period from 1 January 2004 to 1 September 2008, and all cases of colorectal cancer recorded in the National Cancer Registry database from 1 January 2004 to 1 December 2008, were identified. Cases from the two data sets were then matched to identify all patients in whom CTC had been performed more than 6 weeks before a histological report was available. CTC reports and patients' records were reviewed to determine the cancer site, and images were reviewed. A total of 3888 patients underwent CTC over a 56-month interval. After matching with the National Cancer Registry database, colorectal cancer was identified in 131 patients, whereas it had been suspected on CTC in 123 patients. One of the patients with missed cancer was excluded, leaving seven (5.3 per cent) missed cancers, four of which were located in the caecum. Five cancers were missed because of technical limitations of CTC and two were due to perceptive errors. Systems errors and severe patient co-morbidity contributed to three of the cases. The sensitivity of CTC for colorectal cancer was 95 (95 per cent confidence interval 89 to 98) per cent. The sensitivity of 95 per cent for CTC in the diagnosis of colorectal cancer compares favourably with that of double-contrast barium enema (92 per cent) and colonoscopy (94 per cent).

Comparison of CT colonography vs. conventional colonoscopy in mapping the segmental location of colon cancer before surgery

Once presence of a colorectal cancer has been diagnosed, a key factor for patient's prognosis in view of surgical intervention is the correct segmental localization and resection of the tumor. The aim of this work was to compare the accuracy of the current gold standard technique, conventional colonoscopy (CC), to computed tomography colonography (CTC) in the segmental localization of tumor. Sixty-five patients (mean age 64; 45 female and 19 male) with colorectal cancer diagnosed at colonoscopy underwent CTC before surgery. In 45 out of 65 cases (69%), patients were referred to CTC after incomplete CC. Reasons were patient intolerance to CC or presence of stenosing cancer, with consistent difficulties in crossing the tract of the colon involved by the lesion. CTC allowed the complete colonic examination in 63/65 cases, since in 2 patients with an obstructing lesion of the sigmoid colon, pneumocolon could not be obtained. However, per patient and per lesion sensitivity of CTC was 100%. Difference from colonoscopy was statistically significant (P < 0.05). In terms of segmental localization of masses, CTC located precisely all lesions, while colonoscopy failed in 16/67 (24%) lesions, though six were missed for incomplete colonoscopy (9%). In the remaining 10/67 (15%) lesions, detected by colonoscopy but incorrectly located, the mismatch occurred in the rectum (n = 3), sigmoid (n = 2), descending (n = 1), transverse (n = 2), ascending colon, and cecum. Agreement between CTC and CC was fair (k value 0.62). Sensitivity, specificity, positive predictive value and negative predictive value of CTC in determining the precise location of colonic masses were respectively 100%, 96%, 85%, and 100%. CT detected hepatic (6/65 patients) and lung metastases (3/65 patients). CT colonography has better performance in the identification of colonic masses (diameter > 3 cm), in the completion of colonic evaluation and in the segmental localization of tumor. CTC should replace colonoscopy for preoperative staging of colorectal cancer.

Accuracy of Computed Tomographic Colonography for the Detection of Polyps and Colorectal Tumors: A Systematic Review and Meta-Analysis

Background: The real accuracy of computed tomographic colonography (CTC) is still unknown. Objective: To perform a meta-analysis of the diagnostic accuracy of CTC for the detection of polyps and colorectal tumors. Methods: Selection of studies:Studiesassessing the accuracy of CTC for the detection of colorectal polyps and tumors were selected. Data synthesis:Meta-analyses combining sensitivities, specificities and likelihood ratios (LRs) for the diagnosis of polyps and colorectal tumors were carried out. Results: Forty-seven studies, providing data of 10,546 patients, were included. Overall per-polyp sensitivity of CTC was 66% (64–68%), for polyps 6–9 mm in size it was 59% (56–61%), and 76% (73–79%) for polyps larger than 9 mm. Overall per-patient sensitivity was 69% (66–72%), for polyps 6–9 mm 60% (56–65%), and 83% (70–85%) for lesions larger than 9 mm. Overall CTC specificity was 83% (81–84%). Positive and negative LRs were 2.9 (1.8–4) and 0.38 (0.27–0.53), respectively; for polyps 6–9 mm in size, they were 3.8 (2.5–5.7) and 0.4 (0.27–0.59), and 12.3 (7.7–19.4) and 0.19 (0.12–0.3) for polyps larger than 9 mm. Conclusion: CTC is highly specific for the detection of colorectal polyps and tumors. Some studies reported high sensitivities, but the results of the studies were highly heterogeneous, while the studied variables explained only part of this discrepancy.

Should computed tomographic colonography replace optical colonoscopy in screening for colorectal cancer?

Clinical evidence amassed over the last several decades indicates that routine colorectal cancer (CRC) screening, compared to no screening, detects CRC at an earlier stage, reduces the incidence of CRC or the progression early CRC through polypectomy, and reduces CRC mortality. Computed tomographic colonography (CTC) is a minimally invasive, structural evaluation of the entire colorectum that has recently been advocated by multiple American professional medical societies as an effective alternative for CRC screening. The potential advantages of CTC, including rapid image acquisition and processing, non-invasiveness, and decreased procedural risks of perforation, bleeding, and sedation complications may serve to improve the low rates of colorectal cancer screening that are currently observed in our society. Several large studies of CTC as a CRC screening test have reported excellent results but have been criticized because of the expertise of CTC interpreters participating in those trials. As a response to these criticisms, the long-awaited results of the American College of Radiology Imaging Network (ACRIN) National CT Colonography Trial were recently published. The purpose of this study was to assess the accuracy of CTC in a "community based" environment to determine if previous results obtained at expert sites could be replicated. All CTC were confirmed and compared to conventional colonoscopy, the gold-standard colorectal cancer screening test. For polyps >10 mm, the results obtained in the ACRIN trial were comparable to previous studies with a mean CTC sensitivity of 90% and a mean CTC specificity of 86%. The sensitivity of CTC fell to 78% for lesions >6 mm, a value that some studies have suggested is comparable to the detection rate of conventional colonoscopy. This study adds to the body of literature regarding the efficacy of CTC and will likely be cited by many as evidence supporting CTC as an acceptable CRC screening test, in the same league as colonoscopy. Issues remain, however, regarding the extension and reproducibility of these results in the true community setting. There are concerns regarding thresholds for referrals, appropriate intervals between studies, the optimal management of extracolonic findings, and radiation exposure with CTC that remain unanswered by these data.

Impact of Computer-aided Detection on the Cost-effectiveness of CT Colonography

To analyze the cost-effectiveness of adding computer-aided detection (CAD) to a computed tomographic (CT) colonography screening program and to compare it with other options of colorectal cancer (CRC) prevention. The cost-effectiveness of screening strategies by using CT colonography with and without CAD, flexible sigmoidoscopy (FS), and optical colonoscopy were compared by using a Markov-based computer model. In the model, a hypothetical population of 100,000 persons aged 50 years underwent colorectal screening every 10 years. Baseline sensitivities for both experienced and inexperienced readers and the incremental accuracy when adding CAD were estimated from a systematic review of the literature. At baseline, the addition of CAD resulted in 9% and 2% increases in CRC prevention rates for inexperienced and experienced readers, respectively, when compared with CT colonography without CAD. Assuming a CAD cost of $50 per CT colonography, the overall program costs increased by only 3%-5%, largely because of the substantial reduction in CRC-related costs. The incremental cost-effectiveness of CT colonography with CAD compared with CT colonography without CAD was $8661 and $61,354 per life-year gained for inexperienced and experienced readers, respectively. Optical colonoscopy was not a cost-effective alternative to CT colonography with CAD performed by experienced readers, with an incremental cost-effectiveness of $498,668 per life-year gained. CT colonography with CAD for inexperienced readers was more clinically effective and cost-effective than FS. At analysis, sensitivity of CT colonography with CAD for polyps 6 mm or larger was the most meaningful variable. The addition of CAD to CT colonography screening improves the CRC prevention rate, resulting in advantageous cost-effectiveness for screening. http://radiology.rsnajnls.org/cgi/content/full/250/2/488/DC1.

Does a computer-aided detection algorithm in a second read paradigm enhance the performance of experienced computed tomography colonography readers in a population of increased risk?

We prospectively determined whether computer-aided detection (CAD) could improve the performance characteristics of computed tomography colonography (CTC) in a population of increased risk for colorectal cancer. Therefore, we included 170 consecutive patients that underwent both CTC and colonoscopy. All findings >or=6 mm were evaluated at colonoscopy by segmental unblinding. We determined per-patient sensitivity and specificity for polyps >or=6 mm and >or=10 mm without and with computer-aided detection (CAD). The McNemar test was used for comparison the results without and with CAD. Unblinded colonoscopy detected 50 patients with lesions >or=6 mm and 25 patients with lesions >or=10 mm. Sensitivity of CTC without CAD for these size categories was 80% (40/50, 95% CI: 69-81%) and 64% (16/25, 95% CI: 45-83%), respectively. CTC with CAD detected one additional patient with a lesion >or=6 mm and two with a lesion >or=10 mm, resulting in a sensitivity of 82% (41/50, 95% CI: 71-93%) (p = 0.50) and 72% (18/25, 95% CI: 54-90%) (p = 1.0), respectively. Specificity without CAD for polyps >or=6 mm and >or=10 mm was 84% (101/120, 95% CI: 78-91%) and 94% (136/145, 95% CI: 90-98%), respectively. With CAD, the specificity remained (nearly) unchanged: 83% (99/120, 95% CI: 76-89%) and 94% (136/145, 95% CI: 90-98%), respectively. Thus, although CTC with CAD detected a few more patients than CTC without CAD, it had no statistically significant positive influence on CTC performance.

The Efficacy of Intravenous Contrast-enhanced 16-raw Multidetector CT Colonography for Detecting Patients With Colorectal Polyps in an Asymptomatic Population in Korea

The purpose of this study is to compare the sensitivity of computed tomography (CT) colonography (CTC) with that of colonoscopy for detecting patients with colorectal polyps in an asymptomatic screening population in Korea, thus to evaluate a possibility, whether CTC could be used as a screening tool for colorectal polyps. A total of 241 asymptomatic adults underwent intravenous contrast-enhanced CTC and colonoscopy successively on the same day. Bowel preparation was performed by 4 L of polyethylene glycol (n=172) or 90 mL of sodium phosphate (n=69). The CTC findings were released to the colonoscopists after the first examination of each segment, a procedure known as segmental unblinded colonoscopy, and were used as the reference standard. The diagnostic performance of CTC for colorectal polyps was calculated. The per-patient sensitivities of CTC were 68.5% (37/54) and 86.7% (13/15) for polyp > or = 6 and > or = 10 mm, inferior to those of colonoscopy, 92.6% (50/54) and 100% (15/15), respectively. The per-polyp sensitivities of CTC were 60.4% (61/101) and 72.7% (16/22) for polyp > or = 6 and > or = 10 mm, respectively. The low sensitivity of CTC was related with flat morphology. CTC detected only 37.5% (9/24) of flat polyps > or = 6 mm. Bowel preparation by sodium phosphate further decreased the positive predictive value and specificity than by polyethylene glycol. Screening by CTC with asymptomatic population was not promising in Korea despite using advanced CT technology (16-row detector). Bowel preparation was one of the key determinants of the specificity of CTC.

Single-center study comparing computed tomography colonography with conventional colonoscopy

To compare the results from computed tomography (CT) colonography with conventional colonoscopy in symptomatic patients referred for colonoscopy. 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. 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 > or = 6 mm in size. Similarly, specificity for all polyps was 48% (95% CI, 39%-58%) increasing to 67% (95% CI, 56%-76%) for polyps > or = 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. 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.

Computed tomography colonography compared with conventional colonoscopy for the detection of colorectal polyps

Objective To determine the diagnostic accuracy of computed tomography colonography (CTC) compared with conventional colonoscopy (CC). Methods Patients with an indication of CC were included. Fifty patients underwent CTC using multidetector CT before diagnostic colonoscopy was performed by an expert colonoscopist. Diagnostic accuracy was assessed individually both for each polyp and for each patient. Results Fifty patients were included and 40 polyps were analyzed. The by-polyp sensitivity of CTC was 15% for polyps 5 mm or less, 75% for polyps 5-10 mm and 75% for polyps 10 mm or larger. By-patient specificity was 6% for polyps 5 mm or less, 75% for polyps 5-10 mm and 80% for polyps 10 mm or larger. The specificity of CTC was 94%. CTC was preferred over CC by 90% of the patients. The mean colonoscopy examination time was 30 minutes for CC and 35 minutes for CTC (p < 0.05). Conclusions The sensitivity of CTC is moderate in detecting polyps larger than 10 mm, low in detecting 5-10 mm polyps and very low in detecting those less than 5 mm. The overall specificity of the procedure was 94%. Procedure time was lower with CC than with CTC but the latter was better tolerated by most patients.

Cost-effectiveness of computed tomographic colonography: a prospective comparison with colonoscopy

To estimate the cost-effectiveness of detecting colorectal polyps with computed tomographic colonography (CTC) and subsequent polypectomy with primary colonoscopy (CC), using CC as the alternative strategy. A marginal analysis was performed regarding 103 patients who had had CTC prior to same-day CC at two hospitals, H-I (n = 53) and H-II (n = 50). The patients were randomly chosen from surveillance and symptomatic study populations (148 at H-I and 231 at H-II). Populations, organizations, and procedures were compared. Cost data on time consumption, medication, and minor equipment were collected prospectively, while data on salaries and major equipment were collected retrospectively. The effect was the (previously published) sensitivities of CTC and CC for detection of colorectal polyps > or = 6 mm (H-I, n = 148) or > or = 5 mm (H-II, n = 231). Thirteen patients at each center had at least one colorectal polyp > or = 6 mm or > or = 5 mm. CTC was the cost-effective alternative at H-I (euro187 vs. euro211), while CC was the cost-effective alternative at H-II (euro239 vs. euro192). The cost-effectiveness (costs per finding) mainly depended on the sensitivity of CTC and CC, but the depreciation of equipment and the staff's use of time were highly influential as well. Detection of colorectal polyps > or = 6 mm or > or = 5 mm with CTC, followed by polypectomy by CC, can be performed cost-effectively at some institutions with the appropriate hardware and organization.

Review article: population screening for colorectal cancer

Colorectal cancer is a common cancer and common cause of death. The mortality rate from colorectal cancer can be reduced by identification and removal of cancer precursors, adenomas, or by detection of cancer at an earlier stage. Pilot screening programmes have demonstrated decreased colorectal cancer mortality; as a result many countries are developing colorectal cancer screening programmes. The most common modalities being evaluated are faecal occult blood testing, flexible sigmoidoscopy and colonoscopy. Implementation of screening tests has been hampered by cost, invasiveness, availability of resources and patient acceptance. New technologies such at computed tomographic colonography and stool screening for molecular markers of neoplasia are in development as potential minimally invasive tools. This review considers who should be screened, which test to use and how often to screen.

Colon dissection: a new three‐dimensional reconstruction tool for computed tomography colonography

To improve the sensitivity of computed tomography (CT) colonography in the detection of polyps by comparing the 3D reconstruction tool "colon dissection" and endoluminal view (virtual colonoscopy) with axial 2D reconstructions. Forty-eight patients (22 M, 26 F, mean age 57 +/- 21) were studied after intra-anal air insufflation in the supine and prone positions using a 16-slice helical CT (16 x 0.625 mm, pitch 1.7; detector rotation time 0.5 s; 160 mAs und 120 kV) and conventional colonoscopy. Two radiologists blinded to the results of the conventional colonoscopy analyzed the 3D reconstruction in virtual-endoscopy mode, in colon-dissection mode, and axial 2D slices. Conventional colonoscopy revealed a total of 35 polyps in 15 patients; 33 polyps were disclosed by CT methods. Sensitivity and specificity for detecting colon polyps were 94% and 94%, respectively, when using the "colon dissection", 89% and 94% when using "virtual endoscopy", and 62% and 100% when using axial 2D reconstruction. Sensitivity in relation to the diameter of colon polyps with "colon dissection", "virtual colonoscopy", and axial 2D-slices was: polyps with a diameter >5.0 mm, 100%, 100%, and 71%, respectively; polyps with a diameter of between 3 and 4.9 mm, 92%, 85%, and 46%; and polyps with a diameter < 3 mm, 89%, 78%, and 56%. The difference between "virtual endoscopy" and "colon dissection" in diagnosing polyps up to 4.9 mm in diameter was statistically significant. 3D reconstruction software "colon dissection" improves sensitivity of CT colonography compared with the endoluminal view.

Meta-Analysis: Computed Tomographic Colonography

Computed tomographic (CT) colonography, also called virtual colonoscopy, is an evolving technology under evaluation as a new method of screening for colorectal cancer. However, its performance as a test has varied widely across studies, and the reasons for these discrepancies are poorly defined. To systematically review the test performance of CT colonography compared to colonoscopy or surgery and to assess variables that may affect test performance. The PubMed, MEDLINE, and EMBASE databases and the Cochrane Controlled Trials Register were searched for English-language articles published between January 1975 and February 2005. Prospective studies of adults undergoing CT colonography after full bowel preparation, with colonoscopy or surgery as the gold standard, were selected. Studies had to have used state-of-the-art technology, including at least a single-detector CT scanner with supine and prone positioning, insufflation of the colon with air or carbon dioxide, collimation smaller than 5 mm, and both 2-dimensional and 3-dimensional views during scan interpretation. The evaluators of the colonogram had to be unaware of the findings from use of the gold standard test. Data on sensitivity and specificity overall and for detection of polyps less than 6 mm, 6 to 9 mm, and greater than 9 mm in size were abstracted. Sensitivities and specificities weighted by sample size were calculated, and heterogeneity was explored by using stratified analyses and meta-regression. 33 studies provided data on 6393 patients. The sensitivity of CT colonography was heterogeneous but improved as polyp size increased (48% [95% CI, 25% to 70%] for detection of polyps <6 mm, 70% [CI, 55% to 84%] for polyps 6 to 9 mm, and 85% [CI, 79% to 91%] for polyps >9 mm). Characteristics of the CT colonography scanner, including width of collimation, type of detector, and mode of imaging, explained some of this heterogeneity. In contrast, specificity was homogenous (92% [CI, 89% to 96%] for detection of polyps <6 mm, 93% [CI, 91% to 95%] for polyps 6 to 9 mm, and 97% [CI, 96% to 97%] for polyps >9 mm). The studies differed widely, and the extractable variables explained only a small amount of the heterogeneity. In addition, only a few studies examined the newest CT colonography technology. Computed tomographic colonography is highly specific, but the range of reported sensitivities is wide. Patient or scanner characteristics do not fully account for this variability, but collimation, type of scanner, and mode of imaging explain some of the discrepancy. This heterogeneity raises concerns about consistency of performance and about technical variability. These issues must be resolved before CT colonography can be advocated for generalized screening for colorectal cancer.

Computed tomographic colonography without cathartic preparation for the detection of colorectal polyps

We prospectively compared the performance of low-dose multidetector computed tomographic colonography (CTC) without cathartic preparation with that of colonoscopy for the detection of colorectal polyps. A total of 203 patients underwent low-dose CTC without cathartic preparation followed by colonoscopy. Before CTC, fecal tagging was achieved by adding diatrizoate meglumine and diatrizoate sodium to regular meals. No subtraction of tagged feces was performed. Colonoscopy was performed 3-7 days after CTC. Three readers interpreted the CTC examinations separately and independently using a primary 2-dimensional approach using multiplanar reconstructions and 3-dimensional images for further characterization. Colonoscopy with segmental unblinding was used as reference standard. The sensitivity of CTC was calculated both on a per-polyp and a per-patient basis. For the latter, specificity, positive predictive values, and negative predictive values were also calculated. CTC had an average sensitivity of 95.5% (95% confidence interval [CI], 92.1%-99%) for the identification of colorectal polyps > or =8 mm. With regard to per-patient analysis, CTC yielded an average sensitivity of 89.9% (95% CI, 86%-93.7%), an average specificity of 92.2% (95% CI, 89.5%-94.9%), an average positive predictive value of 88% (95% CI, 83.3%-91.5%), and an average negative predictive value of 93.5% (95% CI, 90.9%-96%). Interobserver agreement was high on a per-polyp basis (kappa statistic range, .61-.74) and high to excellent on a per-patient basis (kappa statistic range, .79-.91). Low-dose multidetector CTC without cathartic preparation compares favorably with colonoscopy for the detection of colorectal polyps.

Virtual colonoscopy: Good results and not so good results—why the difference?

Virtual colonoscopy: Good results and not so good results—why the difference?