Role of CT virtual colonoscopy versus conventional colonoscopy in the evaluation of colonic polyps

Virtual colonoscopy is one of the recent advances in the field of CT post processing technique. It represents a type of 3D reconstruction technique which is capable of elaborating endoscopic endoluminal display of the colon without the use of real endoscope and hence it was named virtual colonoscopy. The aim of work is to evaluate the role of virtual colonoscopy in colonic polyps.     

Flat colorectal lesions in asymptomatic adults: implications for screening with CT virtual colonoscopy

OBJECTIVE: The clinical significance of flat lesions in colorectal cancer screening remains uncertain. The purpose of this study was to investigate the frequency, histology, and virtual colonoscopy detection of flat lesions in an asymptomatic screening population. SUBJECTS AND METHODS: The morphology of all detected polyps was prospectively recorded as flat or polypoid (sessile or pedunculated) in 1,233 consecutive asymptomatic adults who underwent same-day virtual colonoscopy and optical colonoscopy. A flat morphology was defined as a shallow plaquelike broad-based lesion with a height of less than one half of its width. RESULTS: Of 344 polyps of 6 mm or greater confirmed at optical colonoscopy, 17 (4.9%) were labeled as flat at both virtual colonoscopy and optical colonoscopy; 17 (4.9%), at optical colonoscopy only; and 25 (7.3%), at virtual colonoscopy only, yielding 59 total lesions in 52 (4.2%) of 1,233 patients. Twenty-nine (49.2%) of 59 flat lesions were adenomatous, of which four measured 10 mm or greater and one 6- to 9-mm lesion was histologically advanced. None of the 148 diminutive flat lesions (< or = 5 mm) detected at optical colonoscopy was histologically advanced. Virtual colonoscopy prospectively detected 24 (82.8%) of 29 flat adenomas and 47 (80.0%) of all 59 flat lesions 6 mm or greater. In comparison, the sensitivity of virtual colonoscopy for the detection of polypoid adenomas and all polypoid lesions of 6 mm or greater was 86.2% (156/181, p = 0.58) and 81.0% (231/285, p = 0.86), respectively. CONCLUSION: Flat adenomas measuring 6 mm or greater are uncommon in a typical Western screening population, and advanced flat neoplasms are rare. The sensitivity of virtual colonoscopy for detecting flat lesions was similar to that of polypoid lesions. These results indicate that flat lesions are not a significant drawback for virtual colonoscopy screening.     

螺旋CT仿真内窥镜诊断大肠息肉初探

目的 探讨螺旋ＣＴ仿真内窥镜对大肠息肉的诊断价值和临床意义。方法 １８例有反复便血、慢性腹泻、腹痛的病人行１次屏气全结肠容积扫描,重叠重建图像并输至工作站进行四维容积重建（４Ｄ ａｎｇｉｏ）,选择导航者（Ｖｏｙａｇｅｒ）软件和合适阈值及透明度,航进观察大肠黏膜。全部资料经纤维结肠镜和（或）手术证实。结果 １８例中发现大肠息肉９例,均为多发,共检出息肉７１枚,直径２～２０ｍｍ,其中升结肠１枚,结肠肝     

CT colonography (virtual colonoscopy): a practical approach for population screening

CT colonography (CTC), also known as virtual colonoscopy, is a minimally invasive test for the detection of colorectal polyps and masses. At the authors' institution, asymptomatic screening has been the overwhelming indication for CTC referral since local third-party coverage was initiated in April 2004. This practical review details the authors' current approach to CTC screening, which has evolved and matured over time. It discusses the entire spectrum from program set-up through patient disposition following CTC examination. The authors hope this article will provide a roadmap for radiologists who wish to institute a CTC screening program.     

Colorectal polyps: detection with dark-lumen MR colonography versus conventional colonoscopy

PURPOSE: To prospectively compare dark-lumen magnetic resonance (MR) colonography with conventional colonoscopy in the detection of colorectal polyps. MATERIALS AND METHODS: Local ethical committee approval and informed consent were obtained. One hundred consecutive patients (56 men, 44 women; mean age +/- standard deviation, 67.7 years +/- 14.7; range, 25-82 years) who were referred for conventional colonoscopy from January 2003 to January 2004 underwent MR colonography and conventional colonoscopy after standard precolonoscopic bowel cleansing. Colonoscopy was performed immediately after MR colonography. For MR colonography, the colon was filled with approximately 2000 mL of tap water. Imaging was performed with a 1.5-T MR unit with patients in the prone position. A T1-weighted three-dimensional volumetric interpolated breath-hold sequence was performed before and 75 seconds after intravenous administration of 0.2 mmol gadobenate dimeglumine per kilogram of body weight. Results of MR colonography were analyzed on a per-polyp and per-patient basis. Findings at colonoscopy were used as the reference for determining accuracy, sensitivity, specificity, and positive and negative predictive values of MR colonography. RESULTS: Of 100 patients recruited for study, 92 (52 men, 40 women; mean age, 61.5 years +/- 14.5; range, 25-82 years) underwent complete MR and conventional colonoscopy examinations. Forty-three of the 92 patients (47%) had normal findings at conventional colonoscopy. In the other 49 patients (53%), conventional colonoscopy depicted 107 polyps (82 adenomas, 25 hyperplastic polyps) and seven carcinomas. At per-polyp analysis, sensitivity of MR colonography in the detection of adenomatous polyps was 100% for polyps at least 10 mm in diameter and 84.2% for polyps 6-9 mm in diameter. At per-patient analysis, the accuracy of MR colonography was 93.1% (sensitivity, 89%; specificity, 96%) if detection of adenomatous polyps of all sizes was considered. CONCLUSION: Dark-lumen MR colonography is a promising modality with high accuracy for detecting colorectal polyps larger than 5 mm in diameter.     

CT虚拟结肠镜对早期筛查结直肠癌的研究进展

CT虚拟结肠镜（CTVC）应用临床以来,在结直肠癌（CRC）的诊断方面越来越显示出其独特的优势,较短的检查时间、较低的辐射剂量和高质量的成像使其成为CRC的早期筛查手段。笔者主要对CTVC在CRC早期筛查方面的进展和临床价值进行综述。     

Colon cancer at barium enema examination and colonoscopy: a study from the county of Hordaland, Norway

PURPOSE: To evaluate the efficacy of barium enema examination as routinely performed in the detection of colon cancer in the inhabitants of a well-defined and circumscribed geographic region. MATERIALS AND METHODS: The study comprised 571 patients with histopathologically verified colon cancer during 1990-1993 from the county of Hordaland. The barium enema examination results were reviewed retrospectively. RESULTS: The correct diagnosis was reached in 351 cases (sensitivity, 90.9%) in 386 tumor locations on the basis of the results of 381 barium enema examinations. Cancer or an important precancerous lesion was overlooked in 26 cases (6.7%), and the examination was not feasible in nine cases (2.3%). The correct diagnosis was reached in 172 cases (sensitivity, 80.0%) in patients with 215 tumor locations on the basis of the results of 213 colonoscopies. Cancer or an important precancerous lesion was overlooked in 13 cases (6.0%). The examination was technically not successful (i.e., the affected area was not reached with the scope) in 30 cases (13.9%). CONCLUSION: Barium enema examination is valuable in the diagnosis of colon cancer and compares favorably with colonoscopy. The main reason for missed radiologic diagnosis is failure to observe important lesions visible on the radiographs.     

Colorectal cancer screening with CT colonography,colonoscopy, and double-contrast barium enema examination: prospective assessment of patient perceptions and preferences

PURPOSE: To prospectively assess and compare perceptions of and preferences for computed tomographic (CT) colonography, colonoscopy, and double-contrast barium enema examination (DCBE) by asymptomatic patients undergoing colorectal cancer screening. MATERIALS AND METHODS: A total of 696 asymptomatic patients at higher-than-average risk undergoing colorectal cancer screening were consecutively recruited to undergo both CT colonography and colonoscopy (group 1), and a like group of 617 patients was separately recruited to undergo both CT colonography and DCBE (group 2). Standard bowel preparations were different between the groups undergoing colonoscopy and DCBE. Each patient completed a questionnaire that assessed preparation inconvenience and discomfort, examination discomfort, willingness to repeat examinations, and examination preference. Survey results were compared for significance by using the Wilcoxon rank sum or chi2 test. RESULTS: The majority of patients considered the preparation to be uncomfortable (group 1, 460 of 515 [89%]; group 2, 482 of 538 [90%]) and inconvenient (group 1, 393 of 502 [78%]; group 2, 427 of 527 [81%]). Reported discomfort was similar at CT colonography and colonoscopy (P =.63) but was less at CT colonography than at DCBE (P <.001). Patients experienced significantly less discomfort than expected at both CT colonography and colonoscopy but not at DCBE. Patients' willingness to undergo frequent rescreening was significantly greater for CT colonography than for either colonoscopy or DCBE. The acceptable time interval between screenings was significantly shorter for all examinations if the bowel preparation could be avoided. Overall, patients preferred CT colonography to colonoscopy (group 1, 72.3% vs 5.1%; P <.001) or to DCBE (group 2, 97.0% vs 0.4%; P <.001). CONCLUSION: Patients undergoing colorectal cancer screening prefer CT colonography to both colonoscopy and DCBE. The majority of patients experience discomfort and inconvenience with cathartic bowel preparation.     

A retrospective evaluation of patient acceptance of computed tomography colonography ("virtual colonoscopy") in comparison with conventional colonoscopy in an average risk screening population

PURPOSE: To evaluate patient acceptance of computed tomography (CT) colonography compared with conventional colonoscopy by means of a self-assessed questionnaire. MATERIAL AND METHODS: Four-hundred-and-one patients with valid address information from our patient collective were preselected. Patient acceptance was evaluated retrospectively using a self-assessed questionnaire. The patients underwent CT colonography in our institution using 4x or 16x multi-detector row (MDR) CT. Two-hundred-and-forty-six patients returned a completed questionnaire, 157 of these indicating that they had undergone both virtual and conventional colonoscopy. RESULTS: One-hundred-and-twenty (76.4%) of the 157 patients would undergo another CT colonography if necessary, while only 14 patients would not. One-hundred-and-sixteen (73.9%) patients favored the actual examination procedure of CT colonography (P<0.0001), while only 6.4% preferred the conventional method. Preparation prior to CT colonography was experienced as more convenient than preparation prior to conventional colonoscopy (52.2% versus 14%). CONCLUSION: CT colonography was preferred in terms of both preparation and the actual procedure itself.     

Computed tomography colonography (virtual colonoscopy): review

Computed tomography examination of the colon performed after bowel cleansing and distension of the lumen with gas goes by several different names--CT colonography (CTC) and CT colography perhaps being the most common. Strictly, the term 'virtual colonoscopy' (VC), should be reserved for the process of examining 3-D, simulated endoluminal images with a capability to navigate through the bowel using appropriate software. Computed tomography colonography appears to be the name that has gained favour among radiologists, although it is suspected that 'virtual colonoscopy' will persist as a generic term due to its attractive 'high-tech' connotations for non-radiological medical and lay persons. Whatever the name, the technique has been made possible through the advent of fast helical CT scanners which allow acquisition of a volume of data, and of proprietary software which enables multiplanar reformatting and 3-D endoluminal reconstructions. It is evident that if CTC/VC can be shown to be acceptable to patients, safe, affordable and accurate, it has enormous potential as a diagnostic and screening tool for colorectal neoplasia.     

New automatic software for virtual colonoscopy: technical aspects

PURPOSE: To evaluate a new virtual endoscopy software package capable of automatically plotting the path along which to perform endoscopic exploration. MATERIALS AND METHODS: We reviewed the examinations of 50 patients with colonic neoplasms studied by CT colonoscopy by using a single-detector CT scanner (Philips Tomoscan AVE1). The technical parameters used were: slice thickness 3 mm, pitch 1.4, reconstruction interval 2-2.5, 120 kV, 150-200 mA. The images were processed on a separate workstation (Philips Easy Vision 5.1) running an experimental virtual endoscopy software package capable of automatically drawing a line along which to move the virtual endoscope to explore the colon. Reconstruction of the endoscopic images along the path obtained was set at an interval of 15-20 mm between one endoscopic view and the next, to a total of 70 to 120 images. The endoscopic animated image sequence was then saved and evaluated by comparing the starting axial images and the three-dimensional images obtained. RESULTS: The programme plotted the endoscopic path correctly in a single pass in 40 of the 50 cases studied. The overall time spent by the radiologist on image-processing did not exceed 5 minutes. DISCUSSION: The need to reduce the time spent by audiologists on post-processing has led to a gradual improvement in image-processing hardware and software. In the context of virtual endoscopy, one of the main goals is to obtain the path for endoscopic exploration in as short a time as possible. The programme we evaluated successfully fulfils this requirement as, once the image-processing technical parameters have been defined, it plots a path along the entire colon and performs the reconstruction procedures automatically. The time spent by the operator on post-processing does not exceed 5 minutes. CONCLUSIONS: The new programme evaluated in this study facilitates the processing of endoscopic images, reduces radiologist time and may contribute to the widespread use of virtual colonoscopy.     

Virtual colonoscopy: issues related to primary screening

Virtual colonoscopy (VC) is a minimally invasive CT examination that has continued to rapidly evolve and improve as a diagnostic screening tool. Current state-of-the-art VC technique has already been shown to be highly effective for screening at the University of Wisconsin. Although more widespread implementation of VC screening faces multiple challenges and barriers, these are all greatly overshadowed by the immediate need for increased patient compliance in effective colorectal screening programs. Given the wide availability of CT and the favorable safety profile compared with optical colonoscopy, VC holds significant potential for addressing a very important yet preventable public health concern. This paper will briefly address some of the major issues related to the general application of VC for colorectal screening, such as diagnostic performance, development of an acceptable screening algorithm, and several technique-related issues.     

Intravenous contrast enhanced computed tomography colonoscopy in children with suspected colonic polyps

Objective

The purpose of this study was to evaluate the diagnostic performance of intravenous contrast enhanced computed tomographic colonoscopy (IVCTC) in the diagnosis of clinically suspected colorectal polyps in children, using conventional colonoscopy (CC) as the gold standard.

Methods

This was a prospective study conducted between July 2008 and June 2010. 30 pediatric patients with history of rectal bleeding and clinically suspected to have colorectal polyps were enrolled. All of the patients underwent IVCTC followed by CC. 30 IVCTC and 31 CC were performed in 30 patients. The findings of IVCTC were compared with those of CC. Statistical analysis was performed to obtain diagnostic performance values of IVCTC on per polyp (sensitivity and positive predictive value) and per patient (sensitivity, specificity, positive predictive value and negative predictive value) basis.

Results

By IVCTC, 63 polyps were detected in 28 patients of which 53 polyps were eligible for inclusion in the statistical analysis. 60 polyps were detected by CC in 28 patients of which 50 polyps were eligible for inclusion in the statistical analysis. The per polyp sensitivity and positive predictive values were 94% and 88.6% respectively. The per patient sensitivity, specificity, positive predictive value, and negative predictive values were 96.4, 50, 96.4, and 50% respectively. Twenty polyps, in 10 patients, were visualized only after intravenous contrast administration of which 5 polyps, in 5 patients, were likely to have been missed in the absence of the intravenous contrast injection as these polyps were submerged in fluid. Four patients would have had a false negative CTC examination if the intravenous contrast had not been injected; while in another patient, the number of polyps would have been underestimated.

Conclusion

CTC is capable of serving as a safe and efficient non-invasive tool for evaluating children with clinically suspected colorectal polyps. Administration of intravenous contrast improves the sensitivity of polyp detection on CTC.