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CT colonography (CTC), also known as “virtual colonoscopy,” is a minimally invasive complementary screening method to optical colonoscopy (OC) that is growing in its availability and utilization. As a screening test, it is typically performed in outpatient radiology sites. Examinations are monitored by a radiologist trained in its performance. CTC is selectively performed in a hospital setting for patients with comorbidities that render them at a high risk for OC, such as cardiac disease or screening before organ transplantation. In cases where OC is unsuccessful for at complete colonic inspection, CTC can be performed the same day after OC or planned at a later date to evaluate the remainder of the colon. Candidates for CTC must be able to follow instructions and tolerate colonic insufflation. Patients who have fecal incontinence or significant rectal prolapse are not candidates for CTC because of limited ability to maintain colonic distension. Finally, strict adherence to the recommended colonic preparation before CTC is critical to the examination's success.

This article reviews alternative colorectal cancer (CRC) screening tests, including flexible sigmoidoscopy (FS), computed tomography (CT) colonography, and colon capsule endoscopy. FS has abundant and convincing evidence supporting its use for CRC screening and is a commonly used CRC test worldwide. CT colonography has demonstrated convincing results for CRC screening, but concerns regarding cost, accuracy for flat or sessile neoplasia, reproducibility, extracolonic findings, and lack of coverage have limited its use and development. Colon capsule endoscopy has demonstrated encouraging results for polyp detection in average-risk individuals, but is not approved for CRC screening at the current time.

Background: Evaluation of segmented colon is one of the challenges in Computed Tomography Colonography (CTC). The objective of the study was to measure the segmented colon accurately using image processing techniques. Methods: This was a retrospective study, and the Institutional Ethical clearance was obtained for the secondary dataset. The technique was tested on 85 CTC dataset. The CTC dataset of 100–120 kVp, 100 mA, and ST (Slice Thickness) of 1.25 and 2.5 mm were used for empirical testing. The initial results of the work appear in the conference proceedings. Post colon segmentation, three distance measurement techniques, and one volumetric overlap computation were applied in Euclidian space in which the distances were measured on MPR views of the segmented and unsegmented colons and the volumetric overlap calculation between these two volumes. Results: The key finding was that the measurements on both the segmented and the unsegmented volumes remain same without much difference noticed. This was statistically proved. The results were validated quantitatively on 2D MPR images. An accuracy of 95.265±0.4551% was achieved through volumetric overlap computation. Through pairedt−test, at α=5%, statistical values were p=0.6769, and t=0.4169 which infer that there was no much significant difference. Conclusion: The combination of different validation techniques was applied to check the robustness of colon segmentation method, and good results were achieved with this approach. Through quantitative validation, the results were accepted at α=5%. Keywords: Euclidean space, Colon segmentation, Quantitative analysis, Spatial features, Volumetric overlap

Significant anxiety has been expressed by some over the radiation risks associated with computed tomography (CT), particularly when it applies to a screening examination such as CT colonography. These theoretic risks are far outweighed by the significant benefits colorectal cancer screening offers. Regardless of how significant the theoretic risk of CT radiation is in the older population, the ALARA principle maintains that radiation dose should be reduced to As Low As Reasonably Achievable. This article will discuss various strategies that may be utilized to reduce radiation dose and mitigate any increase in image noise that may occur.

It is widely accepted that colorectal cancers (CRC) generally derive from once benign dysplastic colorectal polyps. However, it is also true that colorectal polyps are a highly prevalent human condition, affecting the majority of adults according to recent endoscopic screening data. As such, the vast majority of colorectal polyps behave in a benign fashion and will of course never develop into cancer. Furthermore, although the precise timing and sequence of events for progression to cancer have not yet been fully elucidated, the typical dwell time for this infrequent transformation is likely a decade or more, whether via the classic adenoma-carcinoma sequence or the serrated polyp pathway. When taking all these factors into consideration, CRC can clearly be effectively prevented through the detection and removal of benign dysplastic colorectal polyps, but also that a strategy of universal polypectomy is an inefficient approach, leading to excessive resource utilization, costs, and complications. At the other end of the spectrum, tests that primarily target cancer detection ignore the larger benefit of cancer prevention. Between these two extremes, a more rational CRC screening approach that targets large and/or growing polyps and early cancers likely represents a more clinically efficacious and cost-effective strategy. A large and ever-growing volume of data exists surrounding static cross-sectional features of colorectal polyps such as lesion size, morphology, and location – and their relationship to underlying histologic features. Much of this data comes from large colonoscopic databases, where detected polyps are removed without any knowledge of their preceding growth rates. With the emergence of CT colonography (CTC) as an attractive CRC screening tool, we have the ability to follow polyps longitudinally prior to resection. This dynamic in vivo investigation also provides unique opportunities for studying the natural history of polyps, such as correlating growth rates with underlying polyp histology and genetic alterations. These insights could ultimately inform future strategies for screening and surveillance, as well as fuel novel theories on tumor evolution.

Magnetic resonance colonography with its high tissue contrast and without the use of ionizing radiation was designed as a minimally invasive screening tool for colorectal cancer and its precursors. Nonetheless, heterogeneous data on diagnostic performance and patient burden have hindered its use in screening. This article provides an overview on the status and potential of magnetic resonance colonography in the setting of detection and screening of colorectal cancer and its precursors.

Objective To examine the viability of colon cancer screening with computed tomography colonography, also known as virtual colonoscopy. Data Sources Clinical guidelines, published medical research. Conclusion Virtual colonoscopy, under the right circumstances, is an accurate viable screening tool for patients who may not otherwise desire to or are not able to participate in traditional colonoscopy. Implications for Nursing Practice Nurses should be aware that routine colon cancer screening is recommended starting at age 50. In addition to the traditional colonoscopy, there are other options if a patient is unwilling or unable to undergo optical colon screening. Nurses should discuss the positive and negative aspects of different types of colon screening and teach proper bowel preparation for colon screening.

Optical colonoscopy is an invasive procedure used to examine surface lining of the colon, by inserting a flexible tube with a light and camera into the body. Virtual colonoscopy is emerging as a non-invasive alternative to optical colonoscopy. This paper describes 3D reconstruction of colon structure from patient specific CT images, interactive visualization and navigation through the reconstructed colon, automated computation of the navigation path and automated polyp detection with 90.91% sensitivity. This enables a doctor to perform a fast diagnosis through virtual exploration of the colon and resort to invasive colonoscopy procedures only if suspicious polyps are detected.

Novice doctors may watch tutorial videos in training for actual or computed tomographic (CT) colonoscopy. The conventional learning videos can be complemented by virtual colonoscopy software made with a cadaver's sectioned images (SIs). The objective of this study was to assist colonoscopy trainees with the new interactive software. Submucosal segmentation on the SIs was carried out through the whole length of the large intestine. With the SIs and segmented images, a three dimensional model was reconstructed. Six-hundred seventy-one proximal colonoscopic views (conventional views) and corresponding distal colonoscopic views (simulating the retroflexion of a colonoscope) were produced. Not only navigation views showing the current location of the colonoscope tip and its course, but also, supplementary description views were elaborated. The four corresponding views were put into convenient browsing software to be downloaded free from the homepage (anatomy.co.kr). The SI colonoscopy software with the realistic images and supportive tools was available to anybody. Users could readily notice the position and direction of the virtual colonoscope tip and recognize meaningful structures in colonoscopic views. The software is expected to be an auxiliary learning tool to improve technique and related knowledge in actual and CT colonoscopies. Hopefully, the software will be updated using raw images from the Visible Korean project.

Rationale and Objectives This work aimed to study the effects of scanner model and study protocol on radiation dose received by breast tissues from 64-slice computed tomography (CT) studies. Materials and Methods Four scanner models and three study protocols were used in scanning an anthropomorphic phantom with breast modules. Each protocol follows recommendations or guidelines from the American Association of Physicists in Medicine and the American College of Radiology. Twenty thermoluminescent dosimeters were placed inside the breast modules to measure breast tissue doses. Both the absolute and the normalized breast tissue doses were analyzed. Results The mean glandular doses of a lung cancer screening CT, a chest/abdomen/pelvis CT, and a virtual colonoscopy CT are equivalent to less than 1, 5–7, and 1–3 two-view digital mammograms, respectively, for a standard-sized patient. The normalized breast dose differs significantly (P

Colorectal cancer is the second leading cause of cancer-related deaths in the United States. The earlier colorectal cancer is detected, the better chance a person has of surviving 5 years after being diagnosed, emphasizing the need for effective and regular colorectal screening. Computed tomographic colonography has repeatedly demonstrated sensitivities equivalent to the current gold standard, optical colonoscopy, in the detection of clinically relevant polyps. It is an accurate, safe, affordable, available, reproducible, quick, and cost-effective option for colorectal screening and should be considered for mass screening.

Colorectal cancer is a common malignancy affecting over 40,000 people a year in the UK. Most cancers are sporadic but a few, occurring at young age, have a clear genetic basis. Most are situated in the rectum or rectosigmoid and cause rectal bleeding, often with a looser or more frequent stool. Right-sided cancers typically result in anaemia, because the blood in the stool is occult and unnoticed by the patient. Almost all the symptoms of malignancy can also be caused by benign disease. Diagnosis relies on luminal imaging, with colonoscopy being the gold standard. Pre-operative staging should include imaging of the liver and chest with computed tomography. For rectal cancers, magnetic resonance scanning of the pelvis provides accurate information about the local tumour and nodal status, and is used to inform decisions regarding pre-operative chemoradiotherapy. All patients with colorectal cancer should be discussed at multidisciplinary meetings to enable optimum treatment to be determined.

The importance of optical or conventional colonoscopy in diagnosing colon disease is undisputed. In this context, optical colonoscopy is the gold standard against which other techniques must be validated. Apart from enabling direct inspection of the colonic mucosa, optical colonoscopy enables biopsies and techniques to treat and prevent colorectal cancer. Virtual colonoscopy or CT colonography has been validated in multicenter studies; virtual colonoscopy is as sensitive as optical colonoscopy for the detection of polyps and colon cancer. It is currently the only valid alternative to optical colonoscopy. Its role in patients with medium or high risk of colon cancer is in the process of being defined as multidisciplinary teams gain experience. This article aims to discuss the usefulness of virtual colonoscopy in different clinical situations, emphasizing the situations in which there is enough scientific evidence, and to discuss the controversies surrounding its possible use for population-based screening.

Colorectal cancer, which is the third most frequent cancer and the cancer with the second highest mortality rate, frequently develops on a pre-existing adenomatous polyps whose slow growth and malignant degeneration can be identified and controlled by effective screening. Although most lesions can be detected and resected during optical colonoscopy (OC), the cost, risk and poor acceptance of this technique by the general population means that it is reserved for high-risk or very high-risk individuals. The fecal occult blood test (FOBT) (such as the Hemoccult®) is proposed for intermediate-risk individuals between 50 and 75 years old. However, despite the improvements that have been made in this method, sensitivity is low, and although it is simple, it is too rarely used. CT colonography (virtual colonoscopy) is proposed in case of failure, additional risk factors or refusal of optical colonoscopy in high-risk patients or in the presence of a positive FOBT. It should also be proposed as an alternative to the FOBT test to patients who accept the constraints of this technique.

Registration and visualization of surfaces play a significant role in the engineering and medical fields. Especially in virtual colonoscopy (VC), an efficient and robust registration method between supine and prone computed tomography (CT) scans is highly desirable, due to the fact that it helps improve polyp detection rates. However, supine and prone colon registration is still a challenging task due to the large distortion in colon shape. In this work, we present a novel registration and visualization framework for supine and prone colon scans using the optimal mass transport (OMT) theory. The proposed novel method enables parameterization of the colon surface onto the planar rectangle domain for better registration and visualization. Also, we develop novel flattened visualization of the colon wall with magnification of polyps using color-coded distance change in the 2D map. Experimental results validate our proposed registration method and demonstrate the effectiveness and robustness of our method.

Aim To retrospectively study the frequency and magnitude of complications associated with computed tomography (CT) colonography in clinical practice. Methods A questionnaire on complications of CT colonography was sent to Italian public radiology departments identified as practicing CT colonography with a reasonable level of training. The frequency of complications and possible risk factors were retrospectively determined. Responses were collated and row frequencies determined. A multivariate analysis of the factors causing adverse events was also performed. Results 40,121 examinations were performed in13 centers during the study period. No deaths were reported. Bowel perforations occurred in 0.02% (7 exams). All perforations were asymptomatic and occurred in patients undergoing manual insufflation. Five perforations (71%) occurred in procedures performed following a recent colonoscopy. There was no significant difference between perforations associated with rectal balloon (0.017%) and those that were not (0.02%). Complications related to vasovagal reaction (either with or without spasmolytic) occurred in 0.16% (63 exams). All vasovagal reactions resolved in less than 3 h, without any sequelae. Conclusions Perforation rate at CT colonography in Italy is comparable with elsewhere in the world, occurring regardless of the experience of radiology centers. Although the risk is very small, it may not be negligible when compared with the risk of diagnostic colonoscopy.

We can supplement the clinical value of an optical colonoscopy procedure if we can continuously co-align corresponding virtual colonoscopy (from preoperative X-ray CT exam) and optical colonoscopy images. In this work, we demonstrate a computer vision algorithm based on optical flow to compute egomotion from live colonoscopy video, which is then used to navigate and visualize the corresponding patient anatomy from X-ray CT data. The key feature of the algorithm lies in the effective combination of sparse and dense optical flow fields to compute the focus of expansion (FOE); FOE permits independent computation of camera translational and rotational parameters, directly contributing to the algorithm's accuracy and robustness. We performed extensive evaluation via a colon phantom and clinical colonoscopy data. We constructed two colon like phantoms, a straight phantom and a curved phantom to measure actual colonoscopy motion; tracking accuracy was quantitatively evaluated by comparing estimated motion parameters (velocity and displacement) to ground truth. Thirty straight and curved phantom sequences were collected at 10, 15 and 20 mm/s (5 trials at each speed), to simulate typical velocities during colonoscopy procedures. The average error in velocity estimation was within 3 mm/s in both straight and curved phantoms. Displacement error was under 7 mm over a total distance of 287-288 mm in the straight and curved phantoms. Algorithm robustness was successfully demonstrated on 27 optical colonoscopy image sequences from 20 different patients, and spanning 5 different colon segments. Specific sequences among these were chosen to illustrate the algorithm's decreased sensitivity to (1) recording interruptions, (2) errors in colon segmentation, (3) illumination artifacts, (4) presence of fluid, and (5) changes in colon structure, such as deformation, polyp removal, and surgical tool movement during a procedure.

Volumetric colon wall unfolding is a novel method for virtual colon analysis and visualization with valuable applications in virtual colonoscopy (VC) and computer-aided detection (CAD) systems. A volumetrically unfolded colon enables doctors to visualize the entire colon structure without occlusions due to haustral folds, and is critical for performing efficient and accurate texture analysis on the volumetric colon wall. Though conventional colon surface flattening has been employed for these uses, volumetric colon unfolding offers the advantages of providing the needed quantities of information with needed accuracy. This work presents an efficient and effective volumetric colon unfolding method based on harmonic differentials. The colon volumes are reconstructed from CT images and are represented as tetrahedral meshes. Three harmonic 1-forms, which are linearly independent everywhere, are computed on the tetrahedral mesh. Through integration of the harmonic 1-forms, the colon volume is mapped periodically to a canonical cuboid. The method presented is automatic, simple, and practical. Experimental results are reported to show the performance of the algorithm on real medical datasets. Though applied here specifically to the colon, the method is general and can be generalized for other volumes.

The aim of this study was to evaluate the relative values of 2D plane view and 3D intracavity view of CT virtual colonoscopy in displaying colon excavated lesions. Cleaned porcine colon with ulcerative lesion was scanned with multidetector CT. The data were reconstructed and reviewed using 2D plane view and 3D volume-rendered images on a GE AW4.2 workstation. The 3D volume-rendered images showed superiority in displaying excavated lesions.

Detection of potentially subtle abnormalities during diagnostic endoscopy is limited by the quality of the equipment, the skill of the endoscopist, and patient comfort. Rapid advances are occurring in endoscopic technology. Miniature probes offering confocal endomicroscopy, fluorescence, elastic scattering and Raman spectroscopy can all now be used with standard endoscopes. Novel endoscopes such as ‘SpyGlass’ and the ‘Third Eye Retroscope’ have been developed to visualize new regions of the gastrointestinal tract, while the development of thinner more flexible endoscopes, scope-guide systems, colon and pH capsules, and virtual colonoscopy aim to improve patient comfort and satisfaction. While impressive, many of these techniques are still confined to the research arena. The most significant recent advances in routine diagnostic endoscopy are the introduction of high-resolution endoscopes and high-definition TV as well as the introduction of the National Bowel Cancer Screening programme to diagnose and treat colon cancer at a much earlier stage.

Purpose Incidental extracolonic findings affect patient treatment and cost. Therefore, to consider magnetic resonance colonography (MRC) as a tool for colorectal cancer and polyps screening, more knowledge is needed on extracolonic findings. In this study, we sought to determine the prevalence and the spectrum of extracolonic findings in patients with an increased risk colorectal cancer that underwent bright lumen MRC. Materials and methods MRC examinations were performed in 210 patients. A gadolinium solution was administered rectally for distension of the colon. Extracolonic findings were scored by two radiologists and classified by using C-RADS Reporting System. All findings (with advice regarding work-up) were reported to the patient's physician and followed up for 4.5 years on average. Results Extracolonic findings were found in 125 (59.5%) patients. Ten (4.8%) had “potentially important” findings (C-RADS category E4). Twenty-five patients (11.9%) had “likely unimportant” findings (E3), 90 (42.8%) had “clinically unimportant” findings (E2) and 85 (40.5%) had a normal exam (E1). In 14 (6.7%) patients additional work-up was performed for their incidentally discovered lesions. In three of them surgery was performed. After work-up, only in two (1.0%) patients a malignancy was found. Conclusion The number of new relevant extracolonic findings is small and the required additional work-up is limited. This should be considered for implementation of ‘bright lumen’ MRC as a screening tool.

We investigated a Pareto front approach to improving polyp detection algorithms for CT colonography (CTC). A dataset of 56 CTC colon surfaces with 87 proven positive detections of 53 polyps sized 4 to 60 mm was used to evaluate the performance of a one-step and a two-step curvature-based region growing algorithm. The algorithmic performance was statistically evaluated and compared based on the Pareto optimal solutions from 20 experiments by evolutionary algorithms. The false positive rate was lower (p

Background & Aims In patients with polyps detected at computed tomography colonography (CTC) screening, management decisions are influenced by the likelihood of important polyp histology. We assess the rates of cancer and high-grade dysplasia among patients found to have small (6–9 mm) and large (≥10 mm) colorectal polyps at CTC. Methods We reviewed results from 5124 consecutive adults (mean age, 56.9 y; 2792 women) who received CTC screening at 1 institution over a 52-month period. All nondiminutive lesions confirmed at subsequent colonoscopy were grouped by size and histology features. Rates of cancer and high-grade dysplasia were calculated for various sizes. Adenomas were classified as advanced if they were 10 mm or greater and/or contained high-grade dysplasia or a prominent villous component. Results A total of 755 polyps 6 mm or greater were identified during colonoscopy examinations in 479 patients. The rate of malignancy, according to polyp size, was 0% (0 of 464) for polyps 6 to 9 mm, 0.9% (2 of 216) for polyps 10 to 19 mm, 6.1% (2 of 33) for polyps 20 to 29 mm, and 38.1% (16 of 42) for polyps 30 mm or greater. High-grade dysplasia was observed in 0.4% (2 of 464) of 6- to 9-mm polyps and 7.9% (23 of 291) of lesions 10 mm or greater. A prominent villous component was seen in 3.4% (16 of 464) of 6- to 9-mm polyps. The overall rate of advanced histology in small polyps was 3.9% (18 of 464). Conclusions Small (6–9 mm) polyps rarely contained high-grade dysplasia (0.4%); none was malignant. The malignancy rate for large (1–2 cm) colorectal polyps was less than 1%. These findings indicate the potential for less aggressive management of lesions detected by CTC.

This article defines the necessary skill set and knowledge base required for accurate computed tomography colonography (CTC) interpretation. The components of the interpretative process as well as the various strategies currently employed are discussed. The role of extracolonic evaluation as an integral part of this examination is also covered. Within this context, the question of whether a radiologist or gastroenterologist is better suited to interpret this examination is explored.

Objective To determine the usefulness of perspective-filet view for polypoid lesions in paediatric patients in comparison with conventional virtual colonoscopy (VC) analysis and optical colonoscopy. Methods Sixty-one patients (mean age 5 years old) with a previous episode of rectal bleeding were studied using a 16 slices CT scanner. All patients underwent a colonic preparation. Two acquisitions were done in supine and prone positions with slices of 2 mm thickness; increment 1 mm, 30–50 mA; 90–120 kV. In a workstation an experienced radiologist reviewed images twice. The first read was done using the conventional virtual colonoscopy technique with the evaluation of two-dimensional (2D), three-dimensional (3D) and endoscopical images. Later, in a second session, perspective-filet view was used. It shows a 360° unrolled visualization of the inner colon. The presence, size and location of the lesions were determined. A record of the reading time was made. Results At per patient evaluation the conventional virtual colonoscopy analysis obtained a sensitivity of 86% and a specificity of 98%. The perspective-filet view obtained a sensitivity of 91% and a specificity of 99%. In the evaluation on a per lesion basis the conventional analysis had a sensitivity of 81% and a specificity of 88%. Perspective-filet view, had a sensitivity of 82% and specificity of 90%. The average total reading time using conventional colonoscopy technique was 18 ± 3 min, versus 4 ± 1 min using the perspective-filet view. Conclusion Virtual colon dissection with perspective-filet view is more time-efficient than conventional virtual colonoscopy evaluation with correct correlation in results.

Background Unsedated colonoscopy is an uncomfortable procedure for most patients. Discomfort during colonoscopy is largely related to looping of the colonoscope which displaces the colon from its native configuration. Therefore, complete intubation of the colon is considerably difficult in up to 10–20% of procedures. Aims of this study were to determine the “normal” colon anatomy in CT-colonoscopy with special focus on length, number of flexures and tortuosity and to assess frequency and type of looping as well as straightening manoeuvres based on fluoroscopic findings. Methods 100 consecutive screening patients underwent CT colonography and another 100 cases traditional colonoscopy with fluoroscopic aid. Interactive 3D colon maps and 2D MPR images from virtual procedures were reviewed by two experienced GI-radiologists and GI-endoscopists. Colonoscopy was performed by three board-certified gastroenterologists. Fluoroscopic films of each case were recorded and retrospectively analysed. Results There was a considerable difference in overall colonic length between CT colonography and conventional colonoscopy (167 cm vs. 93.5 cm). Number of acute angle flexures and degree of tortuosity was higher in CT colonography than previously assumed. The caecum was reached in 98/100 cases with conventional colonoscopy. Procedures were incomplete due to an obstructing sigmoid cancer and a floppy redundant colon. Looping occurred in 73/100 cases and straightening manoeuvres with fluoroscopy were highly effective in 95%. Looping was more common in older and smaller women. Conclusions Predictive anatomical factors for potentially difficult endoscopic colonoscopy can be defined by CT colonography. Looping occurs frequently during routine colonoscopy but hindered caecal intubation in only one case. Short-term fluoroscopy is extremely helpful to guide straightening and ancillary manoeuvres and should be used selectively in patients with looping during conventional colonoscopy.

The primary goal of colorectal cancer screening and prevention is the detection and removal of advanced neoplasia. Computerized tomography (CT) colonography is now well established as an effective screening test. Areas of greater uncertainty include the performance characteristics of CT colonography for detecting small (6-9 mm), diminutive (< or =5 mm), and flat (nonpolypoid) lesions. However, the actual clinical relevance of small, diminutive, and flat polyps has also been the source of debate. This article addresses these controversial and often misunderstood issues.

To compare the evaluation times and accuracy of unidirectional panoramic three-dimensional (3D) endoluminal interpretation to traditional two-dimensional (2D) and bidirectional 3D endoluminal techniques.Sixty-nine patients underwent computed tomography colonography (CTC) after bowel cleansing. Forty-five had no polyps and 24 had at least one polypor = 6 mm. Patients underwent same-day colonoscopy with segmental unblinding. Three experienced abdominal radiologists evaluated the data using one of three primary interpretation techniques: (1) 2D; (2) bidirectional 3D; (3) panoramic 3D. Mixed model analysis of variance and logistic regression for correlated data were used to compare techniques with respect to time and sensitivity and specificity.Mean evaluation times were 8.6, 14.6, and 12.1 min, for 2D, 3D, and panoramic, respectively. 2D was faster than either 3D technique (p0.0001), and the panoramic technique was faster than bidirectional 3D (p = 0.0139). The overall sensitivity of each technique per polyp and per patient was 68.4 and 76.7% for 2D, 78.9 and 93.3% for 3D; and 78.9 and 86.7% for panoramic 3D.2D interpretation was the fastest overall, the panoramic technique was significantly faster than the bidirectional with similar sensitivity and specificity. The sensitivity for a single reader was significantly lower using the 2D technique. Each reader should select the technique with which they are most successful.

Rationale and Objectives Flat lesions in the colon may result in false-negative computed tomography colonography interpretations. It is unknown whether flat lesions are better measured on two-dimensional (2D) or three-dimensional (3D) images and which settings are optimal for enhanced reproducibility and decreased variability. We evaluated these factors to determine whether 2D or 3D is best for flat lesion measurements. Methods and Materials Eighty-eight lesions in 66 patients from a previously published clinical trial were analyzed. Lesions were viewed with four methods including 2D at three window/level settings and 3D endoluminal view. Lesions in either supine or prone were counted as one dataset. Long axis and height were measured. Criteria of "height" (≤3 mm high) or "ratio" (height ≤half the long axis) were applied. A subset of lesions was subject to inter- and intra-observer variability analysis. Results With the "height" criterion, more datasets were classified as flat in 2D flat ( n = 76), 2D soft tissue ( n = 82), and 3D ( n = 73) views than in the 2D lung ( n = 49) view. If long axis is used as the key metric, endoluminal 3D (12.1%) views significantly showed the least inter-observer variability compared to lung (18.9%) or soft tissue (20.2%) views. Intra-observer variability was low overall for all methods. Conclusion When characterizing lesions as flat, a consistent viewing method should be used. To minimize inter-observer variability (such as when following a patient over time), it is best to use the ratio criterion for flat lesion definition incorporating the single longest dimension on 3D views as the key metric.

Computed tomographic (CT) colonography, also known as virtual colonoscopy or CT colography, is capable of detecting colon polyps and cancers. It is emerging rapidly and has gained great momentum over the past several years, to the point where it has been proposed to be a viable primary colon cancer screening option. Despite the current publicity, many issues concerning CT colonography remain. As of 2009, the following topics are of paramount importance: (1) accuracy, including both sensitivity and specificity, (2) bowel preparation, (3) safety, (4) extracolonic findings, (5) patient acceptability, (6) training and standardization, and (7) implementation of CT colonography. Although much about CT colonography has already been learned, more remains to be learned in the future.

CT colonography (CTC), also termed virtual colonoscopy, is increasingly accepted at sites throughout the world as a new effective tool for the diagnosis and screening of colorectal carcinoma. This article presents information of related issues of bowel cleansing, stool and fluid tagging, bowel distention and multidetector CT scanning parameters. The author presents discussion of interpretation of CTC, appropriate applications of CTC and potential complications.

Rectal bleeding is a very common symptom, with the majority of cases being caused by benign conditions. However, a small but significant percentage of those over 40 will have an underlying colorectal cancer. A careful clinical history is important in making a diagnosis and aiding in the choice of further investigations. These investigations range from flexible sigmoidoscopy, barium enema and colonoscopy to the more recent introduction of virtual colonoscopy and CT colonography. Presentations have been altered by NICE referral guidelines and the introduction of the NHS Bowel Cancer Screening Programme. Management depends on the cause and varies from the conservative through clinic-based procedures to formal surgical interventions.

Digestive endoscopy has been evolving from primary diagnostic to extensive therapeutic modalities in the management of gastrointestinal diseases. The present endoscopic imaging includes (A) standard endoscopy alone and /or with adjunct technologies such as point enhancement, e.g. confocal endomicroscopy and field enhancement technologies such as chromoendoscopy, NBI and FICE and (B) endoscopic ultrasound. Other novel imaging technologies including virtual colonoscopy or CT/MR colonography, CT or MRI enterography and capsule endoscopy have also been developed. This article reviews the diagnostic and therapeutic role of digestive endoscopy and future directions of digestive endoscopy are discussed. Digestive endoscopy is also compared with emerging novel imaging techniques in gastrointestinal diseases such as capsule endoscopy and CT colonography. The fact that digestive endoscopy has become a multidisciplinary specialty combining advances in all fields (radiology, bioengineering, surgery and gastroenterology) is highlighted.

In fecal-tagging CT colonography ( ft CTC), positive-contrast tagging agents are used for opacifying residual bowel materials to facilitate reliable detection of colorectal lesions. However, tagging agents that have high radiodensity tend to artificially elevate the observed CT attenuation of nearby materials toward that of tagged materials on Hounsfield unit (HU) scale. We developed an image-based adaptive density-correction (ADC) method for minimizing such pseudo-enhancement effect in ft CTC data. After the correction, we can confidently assume that soft-tissue materials and air are represented by their standard CT attenuations, whereas higher CT attenuations indicate tagged materials. The ADC method was optimized by use of an anthropomorphic phantom filled partially with three concentrations of a tagging agent. The effect of ADC on ft CTC was assessed visually and quantitatively by comparison of the accuracy of computer-aided detection (CAD) without and with the use of the ADC method in two different types of clinical ft CTC databases: 20 laxative ft CTC cases with 24 polyps, and 23 reduced-preparation ft CTC cases with 28 polyps. Visual evaluation indicated that ADC minimizes the observed pseudo-enhancement effect. With ADC, the free-response receiver operating characteristic curves indicating CAD performance in polyp detection yielded normalized partial area-under-curve values of 0.91 and 0.80 for the two databases, respectively, with statistically significant improvement over conventional thresholding-based approaches ( p

To investigate the effect of a virtual colonoscopy (VC) computed-assisted detection (CAD) system on polyp detection by trained radiographers.Four radiographers trained in VC interpretation and utilization of CAD systems read a total of 62 endoscopically validated VC examinations containing 150 polyps (size range 5-50mm) in four sessions, recording any polyps found and the examination interpretation time, first without and then with the addition of CAD as a "second reader". After a temporal separation of 6 weeks to reduce recall bias, VC examinations were re-read using "concurrent reader" CAD. Interpretation times, polyp detection, and number of false-positives were compared between the different reader paradigms using paired t and paired exact tests.Overall, use of "second reader" CAD significantly improved polyp detection by 12% (p0.001, CI 6%,17%)) from 48 to 60%. There was no significant improvement using CAD as a concurrent reader (p=0.20; difference of 7%, CI -3%, 16%) and no significant overall difference in recorded false-positives with second reader or concurrent CAD paradigms compared with unassisted reading (p=0.25 and 0.65, respectively). The mean interpretation time was 21.7 min for unassisted reading, 29.6 (p0.001) min for second reader and 19.1 min (p=0.12) for concurrent reading paradigms.CAD, when used as a second reader, can significantly improve radiographer reading performance with only a moderate increase in interpretation times.

CT colonography (CTC) is an innovative technology that entails CT examination of the entire colon and computerized processing of the raw data after colon cleansing and colonic distention. CTC could potentially increase the screening rate for colon cancer because of its relative safety, relatively low expense, and greater patient acceptance, but its role in mass colon cancer screening is controversial because of its highly variable sensitivity, the inability to sample polyps for histologic analysis, and lack of therapeutic capabilities. This article reviews the CTC literature, including imaging and adjunctive techniques, radiologic interpretation, procedure indications, contraindications, risks, sensitivity, interpretation pitfalls, and controversies.

Rationale and Objectives The purpose of this study was to assess (1) the agreement of two-dimensional (2D) and three-dimensional (3D) manual and automated polyp linear diameter measurements at CT colonography (CTC), with optical colonoscopic equivalents and (2) intraobserver and interobserver agreement of the CTC measurements. Materials and Methods Using the same CTC system, two radiologists independently measured the maximum linear diameter of 44 polyps (reference size 3–15 mm) matched on CTC and optical colonoscopy: manual 2D optimized multiplanar reformatted planes with standard window settings (level 1500 HU, width −200 HU), manual 3D measurement with software calipers and automated 3D measurement with software. After 2 weeks, polyps were measured again. Compatibility of CTC measurement with that of optical colonoscopy and measurement reproducibility was assessed statistically. Results In the manual measurement, 44 polyps were analyzed and 41 in automated measurement; three polyps could not be extracted. Although the measurement difference was noted for automated, manual 3D, and manual 2D measurements, statistically supported agreement with optical colonoscopic measurement was noted only with manual 2D measurement for both observers. However, 95% limits of agreement were wide for all the measurement methods. When categorized according to the optical colonoscopic measurement, manual 2D, 3D, and automated measurements showed “good” agreement. Although intraobserver and interobserver agreement was good with manual measurement, intraobserver and interobserver agreement was excellent with automated measurement. Conclusion Manual 2D measurements demonstrated trends of better approximation to optical colonoscopy measurements than manual 3D or automated measurements. And automated measurement eliminated intraobserver and interobserver variability. For noninvasive CTC surveillance, manual 2D measurements are expected to measure medium-sized polyps with sufficient agreement with optical colonoscopic measurements and excellent intraobserver and interobserver variability, especially if combined with automated measurement.

Objectives Colorectal cancer (CRC) screening uptake remains poor. Until we understand patient motivation and preferences for undertaking screening, it is unlikely the uptake will be optimal. Our objective is to examine patient preferences for CRC screening modalities and uptake rates using utility-based methods. Methods The preference survey was mailed to a random sample of Canadian subjects aged 40 to 60 years from a primary care network. A fractional factorial experimental design maximized D-efficiency and included four blocks with 12 choice tasks in a conditional two-step design, two-alternative discrete choice format with five screening attributes (process, pain, preparation, sensitivity, and specificity). Bivariate probit regression analysis was used to estimate patient preferences for attributes, choice probabilities for alternative modalities and expected rates of uptake. Results Five hundred forty-seven of 1047 surveys were returned. Almost 30% of respondents preferred no screening. The most preferred test attribute levels were noninvasiveprocess (e.g., CT), no preparation, no pain, 100% specificity, and 90% sensitivity. Accuracy-related attributes were more important than test process-related attributes. Virtual colonoscopy was the most preferred, followed by colonoscopy, barium enema, sigmoidoscopy, and fecal DNA testing, based on simulated choice probability estimates. Fecal occult blood testing (FOBT) was least preferred. Adjusted screening uptake rate estimates showed the greatest impact (42% increase) would be achieved if all CRC screening modalities were available rather than FOBT alone. Conclusion Our findings emphasize the important role of patient preferences for no screening and in selecting alternative CRC screening modalities. CRC screening implementation in Canada should consider patient preferences to optimize uptake.

AIM: Expert consensus recommends directed training and possibly in the future, formal accreditation before independent virtual colonoscopy (VC) reporting. We surveyed radiologists' experience of VC training, compared with barium enema, and assessed attitudes towards accreditation. MATERIALS AND METHODS: A questionnaire was sent to 78 consultant radiologists from 72 centres (65 National Health Service hospitals; seven independent primary screening centres) offering a VC service. RESULTS: Fifty-four (69%) eligible radiologists responded. They had interpreted 18,152 examinations (range 3-1500) in total versus 232,350 (13 times more) barium enemas. Twenty-two (41%) deemed their VC training as inadequate [including five (45%) of screening centre radiologists], and only 14 (26%) had attended a training workshop due to lack of availability (54%) or financial/study leave constraints (24%). Eleven (20%) radiologists routinely double-reported VC examinations versus 37 (69%) barium enemas, yet 21 (39%) considered requirements for VC training were greater than barium enema. Thirty-eight (70%) favoured accreditation beyond internal audit for VC versus 15(28%) for barium enema. Of these 38, seven (18%) favoured "one-off," and 18 (47%) periodic testing, with 16 (42%) favouring external audit alone or in combination with testing. Overall, 42 (78%) considered specific accreditation for reporting screening examinations appropriate and 45 (83%) respondents preferred a national radiological organization to regulate such a scheme. CONCLUSION: There is wide variability in reporting experience and recommendations for VC training have not been widely adopted, in part due to limited access to dedicated workshops. UK radiologists are generally in favour of VC accreditation, governed by a national radiology organization.

Hemoccult II is the only method of screening for colorectal cancer whose effectiveness in reducing specific mortality has been proved by randomized controlled trials. The first experience of French districts based on this strategy reproduced on a population scale the results of the experimental studies. Expanding screening in France to the general public is a public health priority. Large-scale media campaigns, which currently do not exist, could then be launched, and prevention opportunities seized. Immunological tests identifying the presence of blood in the stool have better sensitivity than the guaiac smear tests, especially for the diagnosis of adenomas and to a lesser extent, for that of cancers as a whole. These tests may constitute an alternative to guaiac tests, but are more expensive. Total colonoscopy, proposed every 10 years from the age of 50 years or once in a lifetime around the age of 60 years, is not a realistic method because of its cost and its risks. Sigmoidoscopies are under evaluation in several countries in randomized controlled trials but do not seem appropriate to either the epidemiologic trends of colorectal cancer or to the practice of endoscopy in France. Virtual colonoscopy is an attractive alternative to searching for blood in stool. The evaluation now underway should not interfere with the broad expansion of methods of proven efficacy. Virtual colonoscopy may face competition from numerous emerging techniques of endoscopic exploration of the colon, including the video-capsule. To obtain widespread participation in colorectal cancer screening, policy-makers must take the opinions of healthcare professionals and of the public into account. The medicoeconomic data will be a decisive factor in the choice between these new strategies.

Computed tomographic colonography (CTC), also known as virtual colonoscopy, is an emerging alternative technique for screening of colon cancers. CTC uses CT to provide a series of cross-sectional images of the colon for detection of polyps and masses. Fecal tagging is a means of labeling of residual feces by an oral contrast agent for improving the accuracy in the detection of polyps. Computer-aided diagnosis (CAD) for CTC automatically determines the locations of suspicious polyps and masses in CTC and presents them to radiologists, typically as a second opinion. Despite its relatively short history, CAD has become one of the mainstream techniques that could make CTC prime time for screening of colorectal cancer. Rapid technical developments have advanced CAD substantially during the last several years, and a fundamental scheme for the detection of polyps has been established, in which sophisticated 3D image processing, analysis, and display techniques play a pivotal role. The latest CAD systems indicate a clinically acceptable high sensitivity and a low false-positive rate, and observer studies have demonstrated the benefits of these systems in improving radiologists’ detection performance. Some technical and clinical challenges, however, remain unresolved before CAD can become a truly useful tool for clinical practice. Also, new challenges are facing CAD as the methods for bowel preparation and image acquisition, such as tagging of fecal residue with oral contrast agents, and interpretation of CTC images evolve. This article reviews the current status and future challenges in CAD for CTC without and with fecal tagging.

Aim To investigate interpretative accuracy and reporting time for radiologists performing computed tomography (CT) colonography in day-to-day non-academic clinical practice. Materials and methods Thirteen radiologists from seven centres, who were reporting CT colonography in non-academic daily clinical practice, interpreted a dataset of 15 colonoscopically validated cases in a controlled environment. Ten cases had either a cancer or polyp >10 mm; one case had a medium polyp and four were normal. Correct case categorization and interpretation times were compared using analysis of variance to aggregated results obtained from both experienced observers and observers recently trained using 50 cases, working in an academic environment. The effect of experience was determined using Spearman's rank correlation. Results Individual accuracy was highly variable, range 53% (95% CI 27–79%) to 93% (95% CI 68–100%). Mean accuracy overall was significantly inferior to experienced radiologists (mean 75 versus 88%, p = 0.04) but not significantly different from recently trained radiologists (p = 0.48). Interpretation time was not significantly different to experienced readers (mean 12.4 min versus 11.7, p = 0.74), but shorter than recently trained radiologists (p = 0.05). There was a significant, positive, linear correlation between prior experience and accuracy (p Conclusion Accuracy for sub-specialist radiologists working in a non-academic environment is, on average, equivalent to radiologists trained using 50 cases. However, there is wide variability in individual performance, which generally falls short of the average performance suggested by meta-analysis of published data. Experience improves accuracy, but alone is insufficient to determine competence.

Virtual colonoscopy interpretation is improving rapidly with the development of efficient software using two-dimensional, three-dimensional (3D) endoluminal, and 3D novel views such as those that seem to cut the colon open and lay it flat for interpretation. Comparison of these various views, comparisons of supine and prone positioning, and comparisons of lung and soft tissue windows aid in the recognition of various pitfalls of interpretation.

The double contrast barium enema of the colon continues to be a diffused conventional radiological technique and allows for the diagnosis of neoplastic and inflammatory pathology. After the '70s, a massive initiative is undertaken to simplify, perfect and encode the method of the double contrast barium enema: Altaras from Germany, Miller from USA and Cittadini from Italy are responsible for the perfection of this technique in the last 30 years. The tailored patient preparation, a perfect technique of execution and a precise radiological documentation are essentials steps to obtain a reliable examination. The main limit of double contrast enema is that it considers the pathology only from the mucosal surface. In neoplastic pathology evaluation the main limit is the "T" parameter staging, but more limited are the "N" and "M" parameters evaluation. Today the double contrast technique continues to be a refined, sensitive and specific diagnostic method, moreover, diagnostic results cannot compete with the new CT multislice techniques (CT-enteroclysis and virtual colonoscopy) which can examine both the lumen and the wall of the colon. The double contrast is a cheap and simple examination but in the next future is predictably a progressive substitution of conventional radiology from new multislice techniques, because the cross sectional imaging is more frequently able to detect causes of the symptoms whether resulting both from colonic or non colonic origin.

Virtual colonoscopy (VC) has acquired an important role in evaluation of the colon. In some situations it may be a safer method to visualize the colon effectively, or it may be the only available option when other techniques have failed. This article reviews state-of-the art VC technique and the results of current performance trials. It discusses the rationale for using various colonic cleansing regimens for VC. It also discusses the two distending agents for VC (room air and carbon dioxide) and presents practical tips for administration and the role of antispasmodic drugs.

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.

Comparison of cleansing effects and colonic distension observed with two polyethyleneglycol-solution (PEG) containing bowel preparation techniques prior to CT-colonography (CTC).One hundred and three patients that received CTC in our institution were retrospectively evaluated. Fifty-one patients received preparation 1 (BP1; based on a GoLytely formulation+bisacodyl), 52 preparation 2 (BP2; based on a NuLytely formulation+bisacodyl). On multi-planar-reformatted (MPR) images, fluid residuals and colon distension were assessed in five colonic segments, from the ascending colon to the rectum.On average, significantly (p0.001) lower fluid residuals were assesses when using BP2 regardless of the patient position. In prone position, a significantly lower fluid level was observed in the sigmoid using bowel preparation 2. The average maximum diameter measured for the whole colon was 5.2+/-0.6 cm in prone position and 4.8+/-0.6 cm in the supine position in BP1 (p0.01). In BP2 the average maximum diameter measured for the whole colon was 5.3+/-0.6 cm in prone position and 4.7+/-0.5 cm in supine position, respectively (p0.001).Overall, lower fluid residuals were scored using BP2. In both preparation groups we achieved better colonic distension in prone position. We were not able to distend the sigmoid better when insufflating air during patient repositioning.

Aim The optimal acquisition time for staging colo-rectal carcinoma with a contrast enhanced multidetector CT colonography (CE CTC) has not yet been established. A dual phase with both arterial and portal venous acquisition has been proposed. The purpose of our study is to assess the value of single portal venous phase CE CTC in the preoperative staging of colo-rectal carcinoma. Materials and methods Fifty two (30 M, 22 F; aged 35–82 years) consecutive patients with a histologically proven diagnosis of colo-rectal adenocarcinoma or a highly suspected colo-rectal cancer on conventional colonoscopy underwent a four-slice CE CTC. The procedure was performed 70 s (portal phase) after the intravenous bolus (3 ml/s) administration of 120 ml iodinated non-ionic contrast agent (370 mg iodine/ml). Scans were performed using the following parameters: 2.5 mm beam collimation, pitch 1.25, 120 kV, 200 mAs, rotation time 0.75 s. Images were reconstructed with an effective thickness of 3.2 mm at intervals of 1.6 mm. Two radiologists independently evaluated the depth of tumour invasion into the colo-rectal wall (T), regional lymph node involvement (N), and extracolonic metastases (M). Disagreement was resolved by means of a consensus decision. The pathological results served as the standard of reference. Assessment was made of sensitivity, specificity and accuracy, as well as positive and negative predictive values were assessed. Results CE CTC correctly staged the pT of 52/56 (93%) and the N of 40/56 (71%) lesions, as well as properly identifying 13/14 (93%) extracolonic findings. Conclusion The single portal venous phase CE CTC scanning protocol enables satisfactory preoperative assessment of T, N and M staging in patients with colo-rectal cancer.

Rationale and Objectives This report proposes an alternative method for the automatic detection of colonic polyps that is robust enough to be directly applicable on low-dose computed tomographic data. Materials and Methods The polyp modeling process takes into account both the gray-level appearance of polyps (intensity profiles) and their geometry (extended Gaussian images). Spherical harmonic decompositions are used for comparison purposes, allowing fast estimation of the similarity between a candidate and a set of previously computed models. Starting from the original raw data (acquired at 55 mA), five patient data sets (prone and supine scans) are reconstructed at different dose levels (to 5 mA) by using different kernel filters, slice overlaps, and increments. Additionally, the efficacy of applying an edge-preserving smoothing filter before detection is assessed. Results Although image quality decreases when decreasing acquisition milliamperes, all polyps greater than 6 mm are detected successfully, even at 15 mA. Although not important at high doses, smoothing improves detection results for ultra-low-dose (tube current Conclusion The advantage of low-dose scans is a significant decrease in effective dose from 4.93 to 1.61 mSv while retaining high detection values, particularly important when thinking of population screening.