Diagnostic performance of CT colonography for the detection of colorectal polyps.

OBJECTIVE: To investigate the diagnostic value of CT colonography for the detection of colorectal polyps. MATERIALS AND METHODS: From December 2004 to December 2005, 399 patients underwent CT colonography and follow-up conventional colonoscopy. We excluded cases of advanced colorectal cancer. We retrospectively analyzed the CT colonography findings and follow-up conventional colonoscopy findings of 113 patients who had polyps more than 6 mm in diameter. Radiologists using 3D and 2D computer generated displays interpreted the CT colonography images. The colonoscopists were aware of the CT colonography findings before the procedure. RESULTS: CT colonography detected 132 polyps in 107 of the 113 patients and conventional colonoscopy detected 114 colorectal polyps more than 6 mm in diameter in 87 of the 113 patients. The sensitivity of CT colonography analyzed per polyp was 91% (41/45) for polyps more than 10 mm in diameter and 89% (101/114) for polyps more than 6 mm in diameter. Thirteen polyps were missed by CT colonography and were detected on follow-up conventional colonoscopy. CONCLUSION: CT colonography is a sensitive diagnostic tool for the detection of colorectal polyps and adequate bowel preparation, optimal bowel distention and clinical experience are needed to reduce the rate of missing appropriate lesions.     

Patient acceptance for CT colonography: what is the real issue?

The aim of this study was to evaluate the discomfort associated with CT colonography compared with colonoscopy and bowel purgation cleansing, and to evaluate patient preference between CT colonography and colonoscopy. In a total of 124 patients, scheduled for multidetector virtual CT colonography and diagnostic colonoscopy, patient acceptance and future preference were assessed during the different steps of the procedure (colon preparation, CT examination, and conventional colonoscopy). Patients who described contradictory findings between the degree of discomfort and their preference regarding follow-up examinations were retrospectively reinterviewed regarding the reason for this discrepancy. Colonoscopy was graded slightly more uncomfortable than virtual CT colonography, but the preparation was clearly the most uncomfortable part of the procedure. Concerning their preference regarding follow-up examinations, 71% of the patients preferred virtual CT colonography, 24% preferred colonoscopy, and 5% had no preference. Twenty-eight percent of the patients preferred virtual CT colonography despite that they thought it was equally or even more uncomfortable than colonoscopy. This was mainly due to the faster procedure (17 patients), the lower physical challenge (14 patients), and the lack of sedation (12 patients) of virtual CT colonography. Factors other than the discomfort related to the examinations play an important role in the patient's preference for virtual CT colonography, namely the faster procedure, the lower physical challenge, and the lack of sedation. Since the preparation plays a major decisive factor in the patient acceptance of virtual CT colonography, more attention should be given to fecal tagging.     

CT colonography: comparison of a colon dissection display versus 3D endoluminal view for the detection of polyps

The purpose of this study was to compare sensitivity, specificity, and postprocessing time of a colon dissection approach to regular 3D-endoluminal workup of computed tomography (CT) colonography for the detection of polypoid lesions. Twenty-one patients who had received conventional colonoscopy after CT colonography were selected; 18 patients had either colon polyps or colon cancer and three had no findings. CT colonography was performed using a 4-channel multi-detector-row (MDR) CT in ten cases and a 16-channel MDR-CT in 11 cases. A blinded reader retrospectively evaluated all colonographies using both viewing methods in a randomized order. Thirty-seven polyps were identified by optical colonoscopy. An overall per-lesion sensitivity of 47.1% for lesions smaller than 5 mm, 56.3% for lesions between 5 mm and 10 mm, and 75.0% for lesion larger than 10 mm was calculated using the colon dissection approach. This compared to an overall per-lesion sensitivity of 35.3% (<5 mm), 81.5% (5–10 mm), and 100.0% (>10 mm) using the endoluminal view. The average time consumption for CT colonography evaluation with the colon dissection software was 10 min versus 38 min using the endoluminal view. A colon dissection approach may provide a significant time advantage for evaluation of CT colonography while obtaining a high sensitivity. It is especially superior in the detection of lesions smaller than 5 mm.     

Colonic surveillance by CT colonography using axial images only

Patients at increased risk of colon cancer require strict colon surveillance. Our objective was to establish the efficacy of 2D axial CT colonography as a surveillance test when performed in routine clinical practice. Eighty-two patients at increased risk of colon cancer underwent CT colonography followed by conventional colonoscopy on the same morning. CT colonography studies were performed on a four-ring multidetector CT scanner (100 mAs, 120 kVp, 4×2.5 collimation) and were interpreted by two radiologists using 2D axial images only. Results were correlated with findings at colonoscopy. Note was made of subsequent histology reports from polypectomy specimens. A total of 52 polyps were detected at colonoscopy. Using 2D axial images alone, with no recourse to 2D multiplanar or 3D views, the sensitivity of CT colonography was 100, 33 and 19% for polyps larger than 9, 6–9 and smaller than 6 mm, respectively. Per-patient specificities were 98.8, 96 and 81.5%, respectively. Twenty-nine percent of polyps smaller than 1 cm were adenomatous and there were no histological features of severe dysplasia. CT colonography is a useful colon surveillance tool for patients at increased risk of colon cancer. It has a high specificity for identifying patients who should proceed to colonoscopy and polypectomy, while allowing further colon examination to be deferred in patients with normal studies. Using 2D axial images only, CT colonography can be performed as part of the daily CT workload, with a very low rate of referral for unnecessary colonoscopy.     

Nationwide,Longitudinal Trends in CT Colonography Utilization: Cross-Sectional Survey Results From the 2010 and 2015 National Health Interview Survey

PurposeColon cancer screening reduces deaths from colorectal cancer. Screening rates have plateaued; however, studies have found that giving patients a choice between different screening tests improves adherence. CT colonography is a minimally invasive screening test with high sensitivity for colonic polyps (>1 cm). With increasing insurance coverage of CT colonography nationwide, there are limited estimates of CT colonography utilization over time. Our purpose was to estimate CT colonography utilization over time using nationally representative cross-sectional survey data.MethodsWe utilized 2010 and 2015 National Health Interview Survey cross-sectional data. Participants between ages 50 and 75 without colorectal cancer history were included. Accounting for complex survey design elements, logistic regression analyses evaluated changes in CT colonography utilization over time, adjusted for potential confounders, and stratified by insurance and age.ResultsOverall, 21,686 respondents were included (8,965 in 2010, 12,721 in 2015). Reported CT colonography utilization decreased from 1.2% to 0.9% (odds ratio [OR] 0.92, 95% confidence interval [CI] 0.86-0.98). Stratified analyses revealed no changes in utilization in patients with private insurance (P = .35) and in patients younger than 65 (P = .07). Overall awareness of CT colonography decreased from 20.5% to 15.9% (OR 0.93, 95% CI 0.91-0.95). Reported optical colonoscopy utilization increased from 57.9% to 63.6% (OR 1.03, 95% CI 1.02-1.05).ConclusionDespite increasing self-reported utilization of optical colonoscopy from 2010 to 2015, survey results suggest that CT colonography awareness (～16%) and utilization (～1%) remain low. Improved public awareness and coverage expansion to Medicare-aged populations will promote improved CT colonography utilization and overall colorectal cancer screening rates.     

Automated detection of polyps with CT colonography: evaluation of volumetric features for reduction of false-positive findings

RATIONALE AND OBJECTIVES: To achieve high performance in computer-assisted diagnosis (CAD) of polyps with computed tomographic (CT) colonography, the authors (a) developed new gradient concentration and directional gradient concentration (DGC) features for differentiating between the true-positive and false-positive (FP) findings generated by the authors' CAD scheme, and (b) used receiver operating characteristic (ROC) analysis to quantify the differentiation performance of these and other volumetric features. MATERIALS AND METHODS: CT colonography was performed in 43 patients prone and supine with a helical CT scanner; there were 12 polyps in 11 patients. The polyp candidates generated by the authors' CAD scheme were characterized by nine statistics of six volumetric features, and the resulting 54 feature statistics were combined by a linear or quadratic discriminant classifier. The discrimination performance was measured with round-robin method by ROC analysis and the FP rate of the CAD scheme. RESULTS: The mean value of shape index (SI) yielded the highest individual ROC performance (area under the curve = 0.92). Among combinations, the mean values of SI and DGC and the variance of CT value yielded a high ROC performance (area under the curve = 0.95). With quadratic classifier, the sensitivity and FP rate of the case-based (data set-based) analysis was 100% (95%) with 2.4 FP findings per patient (1.7 FP findings per data set), respectively. CONCLUSION: Combination of the mean values of SI and DGC and the variance of CT value reduced the FP rate substantially without sacrificing sensitivity. These three features are potentially useful in improving the performance of the authors' CAD scheme for detecting polyps with CT colonography.     

CT colonography practice in the UK: a national survey

AIM: To determine the provision of computed tomography (CT) colonography in UK radiology departments. MATERIALS AND METHODS: A questionnaire relating to the availability of CT colonography, barriers to implementation, clinical indications, technique, and practitioners was posted to clinical directors of UK radiology departments. RESULTS: One hundred and thirty-eight departments responded. Fifty (36%) offered CT colonography in day-to-day clinical practice. Of those that did not, 68 of 87 (64%) cited limited scanner capacity as the main barrier. Of the 50 departments offering a service, 39 (78%) offered CT after incomplete colonoscopy, 36 (72%), after failed barium enema, and 37 (74%) as an alternative to barium enema. Of those offering a service, the number of studies performed varied between one per month (38%) to more than one per day (8%). Total experience varied between 20 or fewer studies (28%) to more than 300 (12%). Full bowel preparation was common (92%), as was dual positioning (90%). Colonography was interpreted by radiologists with a subspecialty interest in gastrointestinal imaging in 64% of centres offering a service. CONCLUSION: CT colonography is widely available in the UK, with approximately one-third of responders offering a service. Experience and throughput varies considerably. Limited CT scanner capacity is the major barrier to further dissemination.     

Role of CT colonography in inflammatory bowel disease

CT colonography (CTC), or virtual colonoscopy, is a non-invasive imaging method that uses CT data sets combined with specialized imaging software to examine the colon. CTC is not used routinely in patients with inflammatory bowel disease (IBD). However, investigating contemporarily the colon, other abdominal organs and the peritoneum with CTC is at times useful in patients with IBD, especially when other diagnostic tools fail. Furthermore, since symptoms of colorectal cancer sometimes superimpose to those of inflammatory disease, it may happen to image patients with IBD incidentally. If clinical signs are suggestive for inflammatory disease, exam technique should be modified accordingly and distinguishing radiological findings searched for.     

Intra-individual comparison of patient acceptability of multidetector-row CT colonography and double-contrast barium enema

AIMS: To compare the subjective acceptability of CT colonography in comparison with barium enema in older symptomatic patients, and to ascertain preferences for future colonic investigation. MATERIALS AND METHODS: The study population comprised 78 persons aged 60 years or over with symptoms suggestive of colorectal neoplasia, who underwent CT colonography followed the same day by barium enema. A 25-point questionnaire was administered after each procedure and an additional follow-up questionnaire a week later. Responses were compared using Wilcoxon matched pairs testing, Mann-Whitney test statistics and binomial exact testing. RESULTS: Participants suffered less physical discomfort during CT colonography (p = 0.03) and overall satisfaction was greater compared with barium enema (p = 0.03). On follow-up, respondents reported significantly better tolerance of CT colonography (p = 0.002), and were less prepared to undergo barium enema again (p < 0.001). Of 52 subjects expressing an opinion, all preferred CT to barium enema. CONCLUSION: Patient satisfaction was higher with CT colonography than barium enema. CT colonography caused significantly less physical discomfort and was overwhelmingly preferred by patients.     

Current status on performance of CT colonography and clinical indications

CT colonography (CTC) is a robust and reliable imaging test of the colon. Accuracy for the detection of colorectal cancer (CRC) is as high as conventional colonoscopy (CC). Identification of polyp is size dependent, with large lesions (≥10 mm) accurately detected and small lesions (6–9 mm) identified with moderate to good sensitivity. Recent studies show good sensitivity for the identification of nonpolypoid (flat) lesions as well.     

CT colonography and MR colonography: current status, research directions and comparison

With the introduction of multidetector technology in CT and the moveable table with integrated coil modules in MRI, the concept of multiorgan screening has become realistic. CT colonography and MR colonography are new radiologic techniques that promise to be highly sensitive colorectal screening examinations. This article reviews the current status and research directions in CT colonography and MR colonography, and compares these methods. Received: 9 October 1999; Revised: 10 February 2000; Accepted: 10 February 2000     

Feasibility of ultra-low-dose multislice CT colonography for the detection of colorectal lesions: preliminary experience

Our objective was to evaluate the feasibility of ultra-low-dose scanning for multislice CT colonography in the detection of colorectal lesions. Twenty-seven patients (14 men, 13 women) with clinical indication for conventional colonoscopy were recruited. Multislice spiral CT (Somatom Plus 4 Volume Zoom, Siemens, Germany) examinations were performed after standard oral colonoscopic preparation and colonic distension with room air. Images were acquired using 2.5-mm collimation, 3.0-mm slice thickness, standard reconstruction kernel, 140 kVp, and 10 mAs. Supine and prone acquisitions were obtained in all patients. Images were analyzed on a workstation by two gastrointestinal radiologists. Conventional colonoscopy was performed on the same day in all patients and represented the standard of reference. Total radiation exposure was also calculated. All colorectal cancers were correctly identified at CT colonography (9 of 9, sensitivity 100%). The CT colonography also detected 10 of 12 polyps (overall sensitivity 83.3%). Based on polyp diameter, the sensitivity for the detection of polyps 10 mm or larger was 100% (3 of 3); between 6 and 9 mm, 100% (3 of 3); and 5 mm or smaller, 66.6% (4 of 6). Total radiation exposure for prone and supine acquisitions combined was 1.7 mSv (for men) and 2.3 mSv (for women). Although preliminary, our experience suggests that ultra-low-dose scanning for multislice CT colonography is feasible. This technique provides a sensitivity comparable to that of previous experiences with CT colonography but with a 40–70% reduction of the radiation dose delivered to patients. Electronic Publication     

Efficacy of IV Buscopan as a muscle relaxant in CT colonography

The aim of this study was to examine the efficacy of IV Buscopan as a muscle relaxant in CT colonography in terms of colonic distension and polyp detection, and to determine its particular efficacy in patients with diverticular disease. Seventy-three consecutive patients were randomised to receive IV Buscopan or no muscle relaxant prior to CT colonography. CT colonography was performed using a Siemens Somatom 4-detector multislice CT scanner. The following parameters were recorded: degree of colonic distension using a 4-point scale; diagnostic adequacy of colonic distension; presence or absence of diverticular disease; and presence of colonic polyps. Accuracy of polyp detection was assessed using subsequent conventional colonoscopy as a gold standard. There was no significant difference between the two groups in the number of segments that were deemed to be optimally or adequately distended (p=0.37). Although IV Buscopan did improve distension of certain segments, this effect was not sufficient to improve the number of diagnostically adequate studies in the Buscopan group (p=0.14). In patients with diverticular disease, IV Buscopan did not have any significant effect on segments affected by diverticulosis but was associated with an improvement in distension of more proximal segments. There was no significant difference between the two groups in terms of polyp detection (p=0.34). The addition of prone scanning to supine scanning was found to be the most useful technique for maximising colonic distension. Intravenous Buscopan at CT colonography does not improve the overall adequacy of colonic distension nor the accuracy of polyp detection. In patients with sigmoid diverticular disease IV Buscopan improves distension of more proximal colonic segments and may be useful in selected cases, but our results do not support its routine use for CT colonography.     

Colonography: current status, research directions and challenges. Update 2002

With the introduction of multislice CT technology and faster gradients in MRI, CT and MR colonography are increasingly becoming attractive alternatives for colorectal mass screening. In this article we summarise the current status, research directions, and challenges in CT and MR colonography.     

Bowel preparation for CT colonography

Bowel preparation represents an essential part of CT colonography, as the accuracy of the exam is strongly related to the adequacy of colonic cleansing, and a poor bowel preparation may compromise the diagnostic quality even despite optimization of all other acquisition parameters. Residual stool and fluid in the large bowel may affect the interpretation of the exam and may increase the number of false positives and false negatives. In this regard, the majority of patients having undergone CT colonography state that bowel preparation is the most unpleasant part.     

结肠内容物标记法CT结肠成像的研究进展

结肠镜和传统CT结肠成像检查需要严格的导泻或清洁灌肠,多数年老体弱的病人无法耐受。结肠内容物标记法CT结肠成像是通过口服对比剂来标记肠内残留物质,并结合相关后处理技术有效筛查结直肠病变,避免因物理肠道准备给病人带来的不适与痛苦。就结肠内容物标记法CT结肠成像(双能电子净化方法等)的具体标记方法、影像后处理技术、检查性能及临床意义方面的研究予以综述。     

Effective radiation doses in CT colonography: results of an inventory among research institutions

The purpose of this study was to estimate the effective dose that is currently used in CT colonography using scan parameters that were collected for this purpose, and to investigate trends in time. PubMed was systematically searched from 1996 until January 2004 for studies investigating CT colonography. Research institutions were contacted and asked for their current scan protocol. Thirty-six institutions published 74 studies. Twenty-eight of the 36 institutions provided their current protocol. The median effective dose in 2004 was 5.1 mSv (range 1.2–11.7 mSv) per position. Most institutions (93%) scan in both the supine and prone positions. The median mAs value was 67 mAs (range 20–200), median collimation was 2.5 mm (range 0.75–5). From 1996 until 2004 a significant decrease in mAs and collimation (P=0.006, P<0.0001, respectively) was observed, while institutions that used a multislice scanner increased (P<0.0001). The effective dose remained constant (P=0.76). In 2004 the median effective dose for a complete CT colonography was 10.2 mSv. Despite the increasing use of multislice scanners, which are slightly less dose-efficient, the median effective dose remained approximately constant between 1996 and 2004. This is mainly caused by the use of lower mAs settings.     

Essential requirements of a CT colonography service

There are many potential challenges to developing a high quality, efficient CT colonography service. Some are clear and predictable, for example creating CT capacity and securing financial resources, but some are less obvious, such as harnessing local support or changing referral practice amongst clinical colleagues. Notwithstanding, such barriers will need to be overcome to deliver a well-resourced, successful CT colonography programme. This article utilises the authors’ experience of developing their own CT colonography service from scratch (now examining >1200 patients per annum) and relevant published articles on ‘Standards’ of practice and training to recommend how others might provide CT colonography in their own patient communities. We offer a practical guide and will emphasise the need for a multi-disciplinary approach with locally agreed protocols and service objectives.     

Contrast-enhanced computed tomographic colonography in the follow-up of colorectal cancer patients: a feasibility study

The aim of our study was to assess whether contrast-enhanced CT colonography is a feasible alternative to both conventional colonoscopy and liver ultrasonography in the follow-up program of colorectal cancer patients. Thirty-five patients, surgically treated for colorectal cancer, underwent a follow-up program that included physical examination, carcinoembryonic antigen serum assay, conventional colonoscopy, liver ultrasonography, and chest X-ray. For these patients, we added a yearly contrast-enhanced CT colonography. All CT examinations were performed with a high-resolution protocol using a multidetector spiral CT scanner (Siemens, Erlangen, Germany) prior to and after the administration of 130 ml of i.v. contrast material. Images were directly analyzed on a dedicated workstation by two radiologists to determine colonic evaluation, visualization of colonic anastomosis, presence of polyps, and extra-colonic findings. Colonic evaluation was judged as optimal in 91.7% of all colonic segments. All mechanical surgical anastomoses were visualized with CT colonography. There was no evidence of anastomotic recurrence. Seven polyps were detected in five different patients with CT colonography, with two false-positive and no false-negative examinations. Three liver metastases and two basal pulmonary nodules were also identified. Contrast-enhanced CT colonography is a feasible alternative to both conventional colonoscopy and liver ultrasonography in the follow-up of patients operated on for colorectal cancer. Electronic Publication     

A comparison of primary two- and three-dimensional methods to review CT colonography

The aim of our study was to compare primary three-dimensional (3D) and primary two-dimensional (2D) review methods for CT colonography with regard to polyp detection and perceptive errors. CT colonography studies of 77 patients were read twice by three reviewers, first with a primary 3D method and then with a primary 2D method. Mean numbers of true and false positives, patient sensitivity and specificity and perceptive errors were calculated with colonoscopy as a reference standard. A perceptive error was made if a polyp was not detected by all reviewers. Mean sensitivity for large (≥10 mm) polyps for primary 3D and 2D review was 81% (14.7/18) and 70%(12.7/18), respectively (p-values ≥0.25). Mean numbers of large false positives for primary 3D and 2D were 8.3 and 5.3, respectively. With primary 3D and 2D review 1 and 6 perceptive errors, respectively, were made in 18 large polyps (p = 0.06). For medium-sized (6–9 mm) polyps these values were for primary 3D and 2D, respectively: mean sensitivity: 67%(11.3/17) and 61%(10.3/17; p-values≥ 0.45), number of false positives: 33.3 and 15.6, and perceptive errors : 4 and 6 (p = 0.53). No significant differences were found in the detection of large and medium-sized polyps between primary 3D and 2D review.