Detection of colorectal polyps with CT colography: initial assessment of sensitivity and specificity

Update on Flexible Sigmoidoscopy, Computed Tomographic Colonography, and Capsule Colonoscopy

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.

CT colonography: over two decades from discovery to practice

Since the introduction of CT colonography (CTC) in the mid-1990s, there have been continuous advancements in the examination technique and advanced visualization software for interpretation. This review will cover the origins of CTC as a natural extension of abdominal CT imaging, and discuss the evolution of CTC through the subsequent clinical phases of feasibility, validation, and implementation.

Electronic cleansing in computed tomography colonography using AT layer identification with integration of gradient directional second derivative and material fraction model

Background

In computed tomography colonography images, electronic cleansing (EC) is applied to remove opacified residual materials, called fecal-tagging materials (FTM), using positive-contrast tagging agents and laxative to facilitate polyp detection.

Methods

The proposed EC, EC_prop, integrates the gradient directional second derivative into material fraction model to preserve submerged soft tissue (ST) under FTM. Three-material fraction model is used to remove FTM and artifacts at air-tagging (AT) layers and T-junctions where air, ST, and FTM material meet simultaneously. Moreover, the proposed AT layer identification is used to distinguish AT layers from air-tissue-tagging (ATT) layers in order to preserve ATT layers during cleansing. The clinical evaluation on 467 3-Dimensional band view images was conducted by the abdominal radiologist using four grading levels of cleansing quality with five causes of low quality EC. The amount of the remaining artifacts at T-junctions was approximated from the results of EC_prop. The results from EC_prop were compared with the results from syngo.via Client 3.0 Software, EC_syngo, and the fast three-material modeling, EC_prev, using the preference of the radiologist. Two-tailed paired Wilcoxon signed rank test is used to indicate statistical significance.

Results

The average grade on cleansing quality is 2.89 out of 4. The artifacts at T-junctions from 86.94% of the test images can be removed, whereas artifacts at T-junctions from only 13.06% of the test images cannot be removed. For 13.06% of the test images, the results from EC_prop are more preferable to the results from EC_syngo (p<0.008). For all the test images, the results from EC_prop are more preferable to the results from EC_prev (p<0.001). Finally, the visual assessment shows that EC_prop can preserve ATT layers, submerged polyps and folds while EC_prev can preserve only submerged folds but fails to preserve ATT layers.

Conclusion

From our implementation, EC_prop can improve the performance of the existing EC, such that it can preserve ST, especially ATT layers and remove the artifacts at T-junctions which have never been proposed by any other methods before.

Can CT Virtual Cystoscopy Replace Conventional Cystoscopy in Early Detection of Bladder Cancer?

Aim. To correlate findings of conventional cystoscopy with CT virtual cystoscopy (CTVC) in detecting bladder tumors and to evaluate accuracy of virtual cystoscopy in early detection of bladder cancer. Material and Method. From June 2013 to June 2014, 50 patients (46 males, four females) with history and investigations suggestive of urothelial cancer, with mean age 62.76 ± 10.45 years, underwent CTVC by a radiologist as per protocol and subsequently underwent conventional cystoscopy (CPE) the same day or the next day. One urologist and one radiologist, blinded to the findings of conventional cystoscopy, independently interpreted the images, and any discrepant readings were resolved with consensus. Result. CTVC detected 23 out of 25 patients with bladder tumor(s) correctly. Two patients were falsely detected as negative while two were falsely labeled as positive in CTVC. Virtual and conventional cystoscopy were comparable in detection of tumor growth in urinary bladder. The sensitivity, specificity, positive predictive value, and negative predictive value of virtual cystoscopy were 92% each. Conclusion. CTVC correlates closely with the findings of conventional cystoscopy. Bladder should be adequately distended and devoid of urine at the time of procedure. However, more studies are required to define the role of virtual cystoscopy in routine clinical practice.

Application of MR virtual endoscopy in children with hydrocephalus

PURPOSE

To evaluate the performance of MR virtual endoscopy (MRVE) in children with hydrocephalus.

MATERIALS AND METHODS

Clinical and imaging data were collected from 15 pediatric patients with hydrocephalus and 15 normal control children. All hydrocephalus patients were confirmed by ventriculoscopy or CT imaging. The cranial 3D-T1 weighted imaging data from fast spoiled gradient echo scan (FSPGR) were transported to working station. VE images of cerebral ventricular cavity were constructed with Navigator software.

RESULTS

Cerebral ventricular MRVE can achieve similar results as ventriculoscopy in demonstrating the morphology of ventricular wall or intracavity lesion. In addition, MRVE can observe the lesion from distal end of obstruction, as well as other areas that are inaccessible to ventriculoscopy. MRVE can also reveal the pathological change of ventricular inner wall surface, and help determine patency of the cerebral aqueduct and fourth ventricle outlet.

CONCLUSION

MR virtual endoscopy provides a non-invasive diagnostic modality that can be used as a supplemental approach to ventriculoscopy. However, its sensitivity and specificity need to be determined in the large study.

History, evolution, and current status of radiologic imaging tests for colorectal cancer screening

Colorectal cancer screening is thought to be an effective tool with which to reduce the mortality from colorectal cancer through early detection and removal of colonic adenomas and early colon cancers. In this article, we review the history, evolution, and current status of imaging tests of the colon-including single-contrast barium enema, double-contrast barium enema, computed tomographic (CT) colonography, and magnetic resonance (MR) colonography-for colorectal cancer screening. Despite its documented value in the detection of colonic polyps, the double-contrast barium enema has largely disappeared as a screening test because it is widely perceived as a labor-intensive, time-consuming, and technically demanding procedure. In the past decade, the barium enema has been supplanted by CT colonography as the major imaging test in colorectal cancer screening in the United States, with MR colonography emerging as another viable option in Europe. Although MR colonography does not require ionizing radiation, the radiation dose for CT colonography has decreased substantially, and regular screening with this technique has a high benefit-to-risk ratio. In recent years, CT colonography has been validated as an effective tool for use in colorectal cancer screening that is increasingly being disseminated.

High-definition resolution three-dimensional imaging systems in laparoscopic radical prostatectomy: randomized comparative study with high-definition resolution two-dimensional systems

BACKGROUND

Three-dimensional (3D) imaging systems have been introduced worldwide for surgical instrumentation. A difficulty of laparoscopic surgery involves converting two-dimensional (2D) images into 3D images and depth perception rearrangement. 3D imaging may remove the need for depth perception rearrangement and therefore have clinical benefits.

METHODS

We conducted a multicenter, open-label, randomized trial to compare the surgical outcome of 3D-high-definition (HD) resolution and 2D-HD imaging in laparoscopic radical prostatectomy (LRP), in order to determine whether an LRP under HD resolution 3D imaging is superior to that under HD resolution 2D imaging in perioperative outcome, feasibility, and fatigue. One-hundred twenty-two patients were randomly assigned to a 2D or 3D group. The primary outcome was time to perform vesicourethral anastomosis (VUA), which is technically demanding and may include a number of technical difficulties considered in laparoscopic surgeries.

RESULTS

VUA time was not significantly shorter in the 3D group (26.7 min, mean) compared with the 2D group (30.1 min, mean) (p = 0.11, Student's t test). However, experienced surgeons and 3D-HD imaging were independent predictors for shorter VUA times (p = 0.000, p = 0.014, multivariate logistic regression analysis). Total pneumoperitoneum time was not different. No conversion case from 3D to 2D or LRP to open RP was observed. Fatigue was evaluated by a simulation sickness questionnaire and critical flicker frequency. Results were not different between the two groups. Subjective feasibility and satisfaction scores were significantly higher in the 3D group.

CONCLUSIONS

Using a 3D imaging system in LRP may have only limited advantages in decreasing operation times over 2D imaging systems. However, the 3D system increased surgical feasibility and decreased surgeons' effort levels without inducing significant fatigue.

ACR Appropriateness Criteria colorectal cancer screening

Colorectal cancer is the third leading cause of cancer deaths in the United States. Most colorectal cancers can be prevented by detecting and removing the precursor adenomatous polyp. Individual risk factors for the development of colorectal cancer will influence the particular choice of screening tool. CT colonography (CTC) is the primary imaging test for colorectal cancer screening in average-risk individuals, whereas the double-contrast barium enema (DCBE) is now considered to be a test that may be appropriate, particularly in settings where CTC is unavailable. Single-contrast barium enema has a lower performance profile and is indicated for screening only when CTC and DCBE are not available. CTC is also the preferred test for colon evaluation following an incomplete colonoscopy. Imaging tests including CTC and DCBE are not indicated for colorectal cancer screening in high-risk patients with polyposis syndromes or inflammatory bowel disease. This paper presents the updated colorectal cancer imaging test ratings and is the result of evidence-based consensus by the ACR Appropriateness Criteria Expert Panel on Gastrointestinal Imaging. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Fast three-material modeling with triple arch projection for electronic cleansing in CTC

In this paper, we propose a fast three-material modeling for electronic cleansing (EC) in computed tomographic colonography. Using a triple arch projection, our three-material modeling provides a very quick estimate of the three-material fractions to remove ridge-shaped artifacts at the T-junctions where air, soft-tissue (ST), and tagged residues (TRs) meet simultaneously. In our approach, colonic components including air, TR, the layer between air and TR, the layer between ST and TR (L(ST/TR)), and the T-junction are first segmented. Subsequently, the material fraction of ST for each voxel in L(ST/TR) and the T-junction is determined. Two-material fractions of the voxels in L(ST/TR) are derived based on a two-material transition model. On the other hand, three-material fractions of the voxels in the T-junction are estimated based on our fast three-material modeling with triple arch projection. Finally, the CT density value of each voxel is updated based on our fold-preserving reconstruction model. Experimental results using ten clinical datasets demonstrate that the proposed three-material modeling successfully removed the T-junction artifacts and clearly reconstructed the whole colon surface while preserving the submerged folds well. Furthermore, compared with the previous three-material transition model, the proposed three-material modeling resulted in about a five-fold increase in speed with the better preservation of submerged folds and the similar level of cleansing quality in T-junction regions.

Fold-preserving electronic cleansing using a reconstruction model integrating material fractions and structural responses

In this paper, we propose an electronic cleansing method using a novel reconstruction model for removing tagged materials (TMs) in computed tomography (CT) images. To address the partial volume (PV) and pseudoenhancement (PEH) effects concurrently, material fractions and structural responses are integrated into a single reconstruction model. In our approach, colonic components including air, TM, an interface layer between air and TM, and an interface layer between soft-tissue (ST) and TM (IL ST/TM ) are first segmented. For each voxel in IL ST/TM, the material fractions of ST and TM are derived using a two-material transition model, and the structural response to identify the folds submerged in the TM is calculated by the rut-enhancement function based on the eigenvalue signatures of the Hessian matrix. Then, the CT density value of each voxel in IL ST/TM is reconstructed based on both the material fractions and structural responses. The material fractions remove the aliasing artifacts caused by a PV effect in IL ST/TM effectively while the structural responses avoid the erroneous cleansing of the submerged folds caused by the PEH effect. Experimental results using ten clinical datasets demonstrated that the proposed method showed higher cleansing quality and better preservation of submerged folds than the previous method, which was validated by the higher mean density values and fold preservation rates for manually segmented fold regions.

Virtual cystoscopy (pneumo-cystoscopy)-Its utility in the prospective evaluation of bladder tumor

Aim:

To evaluate the role of virtual cystoscopy (VC) comparing it with cystopanendoscopy (CPE) for detecting bladder tumor(s).

Material and Methods:

Ethical clearance was obtained from the Institutional ethics committee. After an informed consent 30 patients fulfilling the inclusion criteria were enrolled in the prospective non-randomized clinical study and were evaluated as per protocol with VC performed by a qualified radiologist who was blinded to the findings of CPE performed by a qualified urologist. The results so obtained were analyzed using appropriate statistical tools.

Results:

The mean age of the patients was 56 years. Sensitivity of VC in detecting bladder lesions was 92%. However, when axial images were also interpreted along with VC, the sensitivity increased to 96% for detecting bladder lesions. The specificity of VC with axial CT was 40% in respect of detecting bladder lesions. VC with axial CT was 85.7% sensitive in identifying multiple bladder tumors. There were no complications on account of performing VC. Minor problems were encountered with VC and CPE in 16.7% and 13.3% patients respectively.

Conclusions:

VC with axial CT is 96% sensitive in detecting bladder lesions and 85.7% sensitive in detecting the multiplicity of the tumors. VC may be a useful complementary diagnostic tool for the workup of select patients with suspected bladder lesions. However, larger randomized controlled studies are needed to better define the precise clinical and diagnostic role of VC in routine practice.

Settings and Design:

Prospective Clinical Comparative Non Randomized Clinical Study.

Improving Polyp Detection Algorithms for CT Colonography: Pareto Front Approach

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<0.05) by the two-step algorithm than by the one-step for 63% of all possible operating points. While operating at a suitable sensitivity level such as 90.8% (79/87) or 88.5% (77/87), the false positive rate was reduced by 24.4% (95% confidence intervals 17.9-31.0%) or 45.8% (95% confidence intervals 40.1-51.0%) respectively. We demonstrated that, with a proper experimental design, the Pareto optimization process can effectively help in fine-tuning and redesigning polyp detection algorithms.

Colon Capsule Endoscopy compared to Conventional Colonoscopy under routine screening conditions

Background

Colonoscopy (CSPY) for colorectal cancer screening has several limitations. Colon Capsule Endoscopy (PillCam Colon, CCE) was compared to CSPY under routine screening conditions.

Methods

We performed a prospective, single-center pilot study at a University Hospital. Data were obtained from November 2007 until May 2008. Patients underwent CCE on Day 1 and CSPY on Day 2. Outcomes were evaluated regarding sensitivity and specificity of polyp detection rate, with a significance level set at >5 mm.

Results

59 individuals were included in this study, the results were evaluable in 56 patients (males 34, females 22; median age 59). CCE was complete in 36 subjects. Polyp detection rate for significant polyps was 11% on CSPY and 27% on CCE.

6/56 (11%) patients had polyps on CSPY not detected on CCE (miss rate).

Overall sensitivity was 79% (95% confidence interval [CI], 61 to 90), specificity was 54% (95% CI, 35 to 70), positive predictive value (PPV) was 63% and negative predictive value (NPV) was 71%. Adjusted to significance of findings, sensitivity was 50% (95% CI, 19 to 81), specificity was 76% (95% CI, 63 to 86), PPV was 20% and NPV was 93%.

Conclusion

In comparison to the gold standard, the sensitivity of CCE for detection of relevant polyps is low, however, the high NPV supports its role as a possible screening tool.

Trial Registration

NCT00991003.

Colon Capsule Endoscopy compared to Conventional Colonoscopy under routine screening conditions

Background

Nodular regenerative hyperplasia (NRH) has been recently recognized as an emergent cause of liver disease in HIV-infected patients. NRH may cause non-cirrhotic portal hypertension with potentially severe consequences such as refractory ascites, variceal bleeding and hypersplenism. Obliteration of the small intrahepatic portal veins in association with prothrombotic disorders linked to HIV infection itself or anti-retroviral therapy seem to be the causes of NRH and thus the term HIV-associated obliterative portopathy has been proposed.

Case Presentation

Here we describe a case of a HIV-infected patient with biopsy-proven NRH and listed for liver transplantation (LT) because of refractory ascites and repeated upper gastrointestinal bleedings. A transjugular intrahepatic portosystemic shunt was placed as a bridge to LT and did not improve liver function. However, anticoagulant therapy with low-molecular-weight heparin (LMWH) was associated with rapid improvement in the liver condition and allowed to avoid LT in this patient.

Conclusions

Thus, this case underscores the relation between thrombophilia and HIV-associated NRH and emphasizes anticoagulant therapy as possible treatment.

[Evaluation of computed tomographic colonography for detection of colorectal polyps]

BACKGROUND

Computed tomographic colonography has been proposed for detection of colorectal polyps instead of colonoscopy in colorectal cancer screening programs.

AIM

To evaluate the performance of computed tomographic colonography in the detection of colorectal polyps with colonoscopy used as the gold standard.

METHODS

We prospectively studied 20 patients at high risk for colorectal neoplasia (14 men and 6 women; mean age, 55 years and 59 years). Computed tomographic colonography was performed immediately before colonoscopy. We inserted a rectal balloon catheter and insufflated the colon with room air to the level that a good distension was observed. Twenty milligrams of hioscin was given immediately before computed tomographic imaging of the abdomen and pelvis in order to minimize the degree of smooth-muscle spasm and peristalsis and to reduce the patient's discomfort.

RESULTS

Computed tomographic colonography images were considered satisfactory in all cases. Colonoscopy detected 85 polyps in 19 of 20 patients (95%). All the observed polyps were successfully removed and examined histologically. The radiological examination correctly identified 8 of 10 polyps 10 mm or more in diameter, 2 of 19 (18,2%) with 5-9 mm, and just 1 of 53 <5mm (9,1%). Seventeen of the 43 adenomatous polyps were > or =5 mm. Eight (47%) were correctly identified on computed tomographic colonography. None of the neoplasias <5 mm were identified on colonography. Nineteen patients preferred colonoscopy in the event of having to repeat on of the two examinations.

CONCLUSION

For the detection of colorectal polyps, computed tomographic colonography seems to be useful only when the result is positive, as the negative results of this examination cannot eliminate the presence of these lesions.

Virtual endoscopy using CT scan

The term virtual endoscopy refers to using either spiral computed tomography (CT colonography) or magnetic resonance scanning (MR colonography) combined with computer technology to produce high-resolution two- and three-dimensional imaging of the large bowel. Current CT techniques require meticulous bowel preparation and gas insufflation prior to the examination. The advantages of CT colonography over conventional colonography include safety, its ability to demonstrate the entire large bowel in almost all patients, even following incomplete endoscopy, to accurately localize lesions, and to examine the entire colon in patients with obstructing tumors. Additionally, CT colonography allows simultaneous preoperative tumor staging. Screening for colorectal polyps is a controversially discussed indication for CT colonography. Sensitivity and specificity range widely and decrease with decreasing polyp size. However, better results can be achieved using multidetector technology. Most frequently, the examination is well tolerated and assessed by patients to be more acceptable than conventional colonoscopy. There are no reported complications from CT colonography. The procedure requires a scan time of about 25 to 30 seconds with new multidetector CT scanners, and sedation is not used. Currently, CT colonography is less cost-effective than conventional endoscopy. Another disadvantage is the relatively high irradiation exposure associated with CT colonography. Therefore, at the moment, this technique does not appear ready to be included in general screening strategies. However, ongoing and future improvements may prove its value in colorectal examination strategies.

Computed tomographic colonography: current perspectives and future directions

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.

Virtual colonoscopy vs conventional colonoscopy in patients at high risk of colorectal cancer--a prospective trial of 150 patients

OBJECTIVE

Virtual colonoscopy (VC)/CT colonography has advantages over the well-documented limitations of colonoscopy/barium enema. This prospective blinded investigative comparison trial aimed to evaluate the ability of VC to assess the large bowel, compared to conventional colonoscopy (CC), in patients at high risk of colorectal cancer (CRC).

METHOD

We studied 150 patients (73 males, mean age 60.9 years) at high risk of CRC. Following bowel preparation, VC was undertaken using colonic insufflation and 2D-spiral CT acquisition. Two radiologists reported the images and a consensual agreement reached. Direct comparison was made with CC (performed later the same day). Interobserver agreement was calculated using the Kappa method. Postal questionnaires sought patient preference.

RESULTS

Virtual colonoscopy visualized the caecum in all cases. Five (3.33%) VCs were classified as inadequate owing to poor distension/faecal residue. CC completion rate was 86%. Ultimately, 44 patients had normal findings, 44 had diverticular disease, 11 had inflammatory bowel disease, 18 had cancers, and 33 patients had 42 polyps. VC identified 19 cancers--a sensitivity and specificity of 100% and 99.2% respectively. For detecting polyps > 10 mm, VC had a sensitivity and specificity (per patient) of 91% and 99.2% respectively. VC identified four polyps proximal to stenosing carcinomas and extracolonic malignancies in nine patients (6%). No procedural complications occurred with either investigation. A Kappa score achieved for interobserver agreement was 0.777.

CONCLUSION

Virtual colonoscopy is an effective and safe method for evaluating the bowel and was the investigation of choice amongst patients surveyed. VC provided information additional to CC on both proximal and extracolonic pathology. VC may become the diagnostic procedure of choice for symptomatic patients at high risk of CRC, with CC being reserved for therapeutic intervention, or where a tissue diagnosis is required.

Current role and future potential of computed tomographic colonography for colorectal polyp detection and colon cancer screening-incidental findings

AIM

In this retrospective study, we assess the current role and future potential of computed tomographic (CT) colonography as a viable alternative imaging tool for colorectal polyp detection and colon cancer screening.

MATERIALS AND METHODS

Twenty patients have undergone virtual colonographic examinations with 64-multidetector-row spiral CT (MDCT), and three-dimensional images were created on a separate workstation that had the appropriate software for image processing. Images were reviewed by a radiologist, and anatomic division of the entire colon was used to locate the suspected lesions. Characteristics of bowel preparation, intracolonic, extracolonic, and incidental findings were noted, too.

RESULTS

Ten of the 20 patients (50%) had a positive CT colonography for polypoid lesions. Those lesions were distributed into the cecum (4 cases), colon ascendens (2 cases), colon descendens (2 cases), and sigma (2 cases). In 80%, bowel preparation was good, in 15% moderate, and in 5% inadequate. Furthermore, CT scan noted in total 20 incidental findings.

CONCLUSION

CT colonography is currently a viable alternative imaging tool for colorectal polyp detection. There are several clinical situations where CT colonography may play an important role in patient care. These include for example evaluation of the colon after an incomplete conventional colonoscopic examination or evaluation in patients who are clinically unfit to undergo conventional colonoscopy. At centers where there is expertise in data acquisition and interpretation, CT colonography is being offered as a routine imaging examination. With continued improvements in bowel preparation, colonic distention, and CT colonography interpretation by sufficient numbers of radiologists this technology might have a substantial influence on colon cancer screening.

Computed tomography colonography (virtual colonoscopy): climax of a new era of validation and transition into community practice

Colorectal cancer, which kills more than 50,000 patients every year in the United States and costs more than $6 billion in direct health costs, is a prime target for cancer prevention. Computed tomography colonography (CTC) has emerged as a minimally invasive, structural examination of the entire colon that can complement the current tools of cancer prevention and may improve patient compliance. Large trials have suggested a sensitivity of roughly 90% and specificity greater than 97% for CTC for patients with polyps >or= 10 mm. Bowel preparation by diet restriction, catharsis, and stool and fluid tagging are typically used. A prepless CTC protocol is an active area of research with a focus on improving patient compliance. Insurance coverage of CTC is a key factor affecting current dissemination and local and national coverage decisions are ongoing. CT examination of the abdomen allows visualization of extracolonic organs, where detection of additional disease must balance any unnecessary anxiety and testing. Estimates of CTC cost-effectiveness are generally favorable, but vary due to the high sensitivity of these models to costs, polyp sensitivity, compliance rates, and other parameters, which are difficult to accurately assess. Quality initiatives are being developed that will be key for implementation into community practice.

Findings on optical colonoscopy after positive CT colonography exam

BACKGROUND & AIMS

The aim of this study is to evaluate the findings on optical colonoscopy (OC) after a positive CT colonography (CTC) exam and characterize the type of polyps seen on OC but not reported by CTC.

METHODS

Over an 18-month period a total of 159 asymptomatic adults had polyps seen on computed tomography colonography examination and subsequently underwent planned therapeutic optical colonoscopy. The colonoscopists were aware of the findings on CT colonography prior to further evaluation of the colon. Characteristics of polyps and adenomas seen on subsequent optical colonoscopy but not seen or reported on CT colonography were examined.

RESULTS

The adenoma miss rate for CT colonography overall was 18.9% (25/132) including 6.2% (4/65) for polyps >9 mm and 18.2% (8/44) for polyps 6-9 mm. Three of the adenomas >9 mm not seen on CTC were sessile, and two were found in patients with technically difficult CT colonography studies due to poor colonic distention. No adenomas with advanced pathology <6 mm were found on optical colonoscopy but not reported on CT colonography. False-positive CTC referral where no polyp was seen on colonoscopy was 5.0%.

CONCLUSIONS

CT colonography has adenoma miss rates similar to miss rates historically found with optical colonoscopy, with most missed adenomas being <10 mm and sessile in shape.

Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology

In the United States, colorectal cancer (CRC) is the third most common cancer diagnosed among men and women and the second leading cause of death from cancer. CRC largely can be prevented by the detection and removal of adenomatous polyps, and survival is significantly better when CRC is diagnosed while still localized. In 2006 to 2007, the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology came together to develop consensus guidelines for the detection of adenomatous polyps and CRC in asymptomatic average-risk adults. In this update of each organization's guidelines, screening tests are grouped into those that primarily detect cancer early and those that can detect cancer early and also can detect adenomatous polyps, thus providing a greater potential for prevention through polypectomy. When possible, clinicians should make patients aware of the full range of screening options, but at a minimum they should be prepared to offer patients a choice between a screening test that primarily is effective at early cancer detection and a screening test that is effective at both early cancer detection and cancer prevention through the detection and removal of polyps. It is the strong opinion of these 3 organizations that colon cancer prevention should be the primary goal of screening.

Spectrum of normal findings, anatomic variants and pathology of ileocecal valve: CT colonography appearances and endoscopic correlation

Knowledge of the potential variants of ileocecal valve, the most frequent pathologic conditions as well as some pitfalls encountered during the analysis of CT Colonography images are thus indispensable for radiologists who perform and interpret such examinations and for general practitioners who are approaching this technique. Awareness of these different diagnostic possibilities is mandatory for radiologists evaluating CT Colonography datasets. Combined analysis of 2D axial and reformatted slices and 3D endoluminal views provides the highest level of diagnostic accuracy. We present the multidetector CT Colonography findings with endoscopic correlation and discuss the possible pathologies and the practical implications.

Critical analysis of the performance of double-contrast barium enema for detecting colorectal polyps > or = 6 mm in the era of CT colonography

OBJECTIVE

The purpose of our study was to perform a meta-analysis comparing the performance of double-contrast barium enema (DCBE) with CT colonography (CTC) for the detection of colorectal polyps > or = 6 mm using endoscopy as the gold standard.

MATERIALS AND METHODS

Prospective DCBE and CTC studies were identified. Percentages of polyps and of patients with polyps > or = 10 mm and 6-9 mm were abstracted. The performance of DCBE versus CTC was determined by separately evaluating each technique's performance versus that of endoscopy, and contrasting the techniques. The I-squared statistic and Fisher's exact test were used for heterogeneity, the Cochran-Mantel-Haenszel and the Kruskal-Wallis tests for correlation, and the A(z) test for comparing pooled weighted estimates of performance.

RESULTS

Eleven studies of DCBE (5,995 patients, 1,548 polyps) and 30 studies of CTC (6,573 patients, 2,348 polyps) fulfilled inclusion criteria. For polyps > or = 10 mm, a 0.121-per-patient sensitivity difference favored CTC (p < 0.0001; DCBE, 0.702 [95% CI, 0.687-0.715]; CTC, 0.823 [0.809-0.836]). For polyps > or = 10 mm, a 0.031-per-polyp sensitivity difference favored CTC (p < 0.0001; DCBE, 0.715 [0.703-0.726]; CTC, 0.746 [0.735-0.757]). For polyps > or = 10 mm, a specificity difference of 0.104 favored CTC (p = 0.001; DCBE, 0.850 [0.847-0.855]; CTC, 0.954 [0.952-0.955]). DCBE was also significantly less sensitive for 6- to 9-mm polyps (p < 0.001).

CONCLUSION

DCBE has statistically lower sensitivity and specificity than CTC for detecting colorectal polyps > or = 6 mm.

Impact of a CT colonography screening program on endoscopic colonoscopy in clinical practice

OBJECTIVE

The potential effect of CT colonography (CTC) on endoscopic colonoscopy (EC) has been the topic of much speculation. The aim of this study was to evaluate the impact of a CTC screening program on colonoscopy in clinical practice.

METHODS

At our institution a third-party reimbursed CTC colorectal cancer (CRC) screening program was established in 2004. The number of CTC monthly exams performed, monthly EC total and screening exams performed, EC with polypectomy performed, and the number of referrals for EC screening exams requested were prospectively examined in the first 33 months after introduction of a CTC CRC screening program.

RESULTS

The mean number of overall (378.5 vs 413.1) and screening (150.7 vs 162.9) colonoscopy exams performed per month did not change significantly after screening CTC was introduced. The mean number of monthly CTC exams performed rose significantly throughout the first year of the study from 39 initially to a peak of 147.6 cases per month but decreased slightly to 114.3 monthly exams at the end of 2006. A mean 10.0 patients per month were sent for EC after a positive CTC exam. The mean number of monthly colonoscopies with polypectomy remained constant after the introduction of CTC (197.0 vs 180.2). Monthly referrals for screening EC exams initially decreased but were unchanged 3 yr after institution of a CTC screening program (255.0 vs 253.5).

CONCLUSIONS

(a) In our tertiary care center the initiation of a screening CTC program did not result in a decrease in the number of total colonoscopy exams, screening colonoscopy exams performed, nor requests for screening colonoscopy. (b) Only a small number of CTC exams were referred for EC with polypectomy, therefore a CTC screening program may not increase the overall number of therapeutic colonoscopies performed.

Colon polyp detection using smoothed shape operators: preliminary results

Computer-aided detection (CAD) algorithms identify locations in computed tomographic (CT) images of the colon that are most likely to contain polyps. Existing CAD methods treat the CT data as a voxelized, volume image. They estimate a curvature-based feature at the mucosal surface voxels. However, curvature is a smooth notion, while our data are discrete and noisy. As a second order differential quantity, curvature amplifies noise. In this paper, we present the smoothed shape operators method (SSO), which uses a geometry processing approach. We extract a triangle mesh representation of the colon surface, and estimate curvature on this surface using the shape operator. We then smooth the shape operators on the surface iteratively. Throughout, we use techniques explicitly designed for discrete geometry. All our computation occurs on the surface, rather than in the voxel grid. We evaluate our algorithm on patient data and provide free-response receiver-operating characteristic performance analysis over all size ranges of polyps. We also provide confidence intervals for our performance estimates. We compare our performance with the surface normal overlap (SNO) method for the same data. A preliminary evaluation of our method on 35 patients yielded the following results (polyp diameter range; sensitivity; false positives/case): (10mm; 100%; 17.5), (5-10 mm; 89.7%, 21.23), (<5 mm; 59.1%; 23.9) and (overall; 80.3%; 23.9). The evaluation of the SNO method yielded: (10 mm; 75%; 17.5), (5-10 mm; 43.1%; 21.23), (<5 mm; 15.9%; 23.9) and (overall; 38.5%; 23.9).

Role of computed tomographic colonoscopy of postoperative surveillance in patient with gastric cancer

AIM: To examine the diagnostic yield of colorectal neoplasia at computed tomographic colonoscopy (CTC) as well as the feasibility of contrast enhanced CTC in patients with gastric cancer.

METHODS: To examine the incidence of colon polyp we selected postoperative 188 gastric cancer patients, which we refer to as the 'colon polyp survey group'. To examine the feasibility of CTC for early detection of colon cancer or advanced colon adenoma, we selected 47 gastric cancer patients (M:F 29:18, mean age 53.8 years), which we call the 'CT colonoscopy group'. All the 47 patients underwent successive CTC and colonoscopy on the same day.

RESULTS: Totally 109 colon polyps were observed from 59 out of 188 gastric cancer patients, the incidence rate of colon polyps in gastric cancer patients being 31.4%. The sensitivity of CTC in detecting individuals with at least 1 lesion of any size was 57.1%, the specificity was 72.7%, the positive predictive value was 47.1%, and the negative predictive value was 71.9%. When the cutoff size was decreased to 6 mm, the sensitivity and specificity were 80.0% and 92.9%, respectively, with positive and negative predictive values of 57.1% and 97.5%, respectively. Only one patient was classified as false negative by virtual colonoscopy.

CONCLUSION: The diagnostic yield of colorectal polyp was 31.4% in patients with gastric cancer, and contrast enhanced CTC is an acceptable tool for the detection of synchronous colorectal advanced adenoma and postoperative surveillance of gastric cancer patients.

Meta-analysis comparing CT colonography, air contrast barium enema, and colonoscopy

INTRODUCTION

Published studies have reported a wide range of sensitivities and specificities for computed tomographic (CT) colonography for polyp detection, generating controversy regarding its diagnostic accuracy.

METHODS

A meta-analysis of published studies comparing the accuracies of CT colonography and colonoscopy for polyp detection was performed. The pooled per-patient sensitivities and specificities were calculated at various thresholds for polyp size. Summary receiver operating characteristic (sROC) curves were also constructed.

RESULTS

Thirty studies were included in the meta-analysis of CT colonography. The pooled per-patient sensitivity of CT colonography was higher for polyps greater than 10 mm (0.82, 95% confidence interval [CI], 0.76-0.88) compared with polyps 6 to 10 mm (0.63, 95% CI, 0.52-0.75) and polyps 0 to 5 mm (0.56, 95% CI, 0.42-0.70). Similarly, the exact area under the sROC curve (area +/- standard error) was higher using a threshold greater than 10 mm (0.898 +/- 0.063) compared with thresholds of greater than 5 mm and any size (0.884 +/- 0.033 and 0.822 +/- 0.059, respectively). There were no significant differences in the diagnostic characteristics of 2-dimensional versus 3-dimensional CT colonography. At a threshold greater than 5 mm, the exact area under the sROC curve was significantly higher for endoscopic colonoscopy compared with CT colonography (0.998 +/- 0.006 vs 0.884 +/- 0.033, P < .005).

CONCLUSIONS

CT colonography has a reasonable sensitivity and specificity for detecting large polyps but was less accurate than endoscopic colonoscopy for smaller polyps. Thus, CT colonography may not be a reasonable alternative in situations in which a small polyp may be clinically relevant.

Frequency and impact of extracolonic findings detected at computed tomographic colonography in a symptomatic population

Background

Extracolonic findings are frequently recognized alongside colonic pathology at computed tomographic colonography (CTC). This study assessed the clinical impact of extracolonic findings in a symptomatic population at high risk of colorectal cancer.

Methods

CTC was performed in a consecutive cohort of patients assessed in a fast-track colorectal cancer clinic as being at high risk of colorectal cancer. A review of CTC findings and case notes was undertaken. Patients with extracolonic findings were followed up for at least 12 months.

Results

Thirty-one (13·8 per cent) of 225 patients investigated by CTC had colorectal cancer. Extracolonic findings were identified in 81 (53·3 per cent) of 152 patients with normal or non-neoplastic bowel findings, compared with 27 (37 per cent) of 73 patients with colorectal neoplasia (P = 0·025). Twenty-four patients (10·7 per cent) with extracolonic findings underwent further investigation or treatment. The median duration of investigation was 19·5 weeks. Seventy-five clinical events were recorded, including 14 surgical procedures.

Conclusion

A prospective cost–benefit analysis of diagnostic CTC should be performed before it is established as a first-line investigation for colonic symptoms.

Revisiting oral barium sulfate contrast agents

Oral contrast agents used during CT colonography (CTC) are valuable and may reduce false positive and false negative detections due to stool and residual fluid. Electronic cleansing algorithms are feasible, and oral contrast agents can eliminate the CTC requirement for a clean colon. Recent work shows oral contrast frequently adheres to polyps, with a preference for those with villous histology, a characteristic of advanced polyps. This finding encourages the development of contrast agents that highlight polyps at greatest risk for progression to malignancy. Our review summarizes numerous aspects of oral barium sulfate contrast agents as well as tests to assess adherence and coating ability of the agents, offering arenas to explore and tools for evaluation.

Diagnostic Potential of Three-Dimensional Ultrasound-Based Virtual Cystoscopy

OBJECTIVE

We sought to investigate the feasibility of 3-dimensional ultrasound (3D US)-based virtual cystoscopy in experimentally designed bladder phantoms using pig bladders.

MATERIALS AND METHODS

Ten bladder phantoms with simulated polypoid tumors of different sizes were constructed to provide 3D US-based virtual cystoscopic images. The simulated polypoid tumors were divided by their location into 2 groups: group 1 included the polyps on the anterior and posterior walls, and group 2 included those on the remaining 4 walls. Two genitourinary radiologists independently interpreted the virtual cystoscopic images, with a consensus reached for cases with discrepant results.

RESULTS

In a consensus reading, 3D US-based virtual cystoscopy detected 44 (91.7%) of 48 polypoid lesions. All lesions (n = 4) with false-negative results were 5 mm or smaller in diameter, and so the detection rate was 81.8% (18/22) for lesions 5 mm or smaller whereas it was 100% (26/26) for lesions larger than 5 mm. The detection rate for group 1 (93.8%) was not significantly different from that for group 2 (90.6%; P = 1.000). There were 7 false-positive lesions. Of these, 5 lesions were seen in group 1, and reverberation artifacts were the most common source of these errors (n = 4). Blind areas were present in 19 (31.7%) of 60 virtual cystoscopic images and were seen only in group 2. The differences in the false-positive rate and the incidence of blind area were statistically significant between both groups (P = 0.036, P = 0.00008, respectively).

CONCLUSION

3D US-based virtual cystoscopy may have diagnostic potential in the detection of polypoid bladder tumors.

Screening for colon cancer

Colorectal cancer screening reduces mortality in individuals 50 years and older. Each of the screening tests currently available has advantages and limitations, and there is no consensus as to which test or combination of tests is best. What is clear, however, is that the rates of colorectal cancer screening remain low. This review summarizes the clinical evidence supporting colorectal cancer screening in the average risk population and in high risk groups, discusses the advantages and disadvantages of the available screening tests, outlines the currently recommended guidelines for screening based on risk category, and discusses new and emerging technologies for colorectal cancer screening.

An improved electronic colon cleansing method for detection of colonic polyps by virtual colonoscopy

Electronic colon cleansing (ECC) aims to segment the colon lumen from a patient abdominal image acquired using an oral contrast agent for colonic material tagging, so that a virtual colon model can be constructed. Virtual colonoscopy (VC) provides fly-through navigation within the colon model, looking for polyps on the inner surface in a manner analogous to that of fiber optic colonoscopy. We have built an ECC pipeline for a commercial VC navigation system. In this paper, we present an improved ECC method. It is based on a partial-volume (PV) image-segmentation framework, which is derived using the well-established statistical expectation-maximization algorithm. The presented ECC method was evaluated by both visual inspection and computer-aided detection of polyps (CADpolyp) within the cleansed colon lumens obtained using 20 patient datasets. Compared to our previous ECC pipeline, which does not sufficiently consider the PV effect, the method presented in this paper demonstrates improved polyp detection by both visual judgment and CADpolyp measure.

Occult colorectal polyps on CT colonography: implications for surveillance

OBJECTIVE

Our purpose was to determine the prevalence of polyps that are invisible on CT colonography (CTC) in a population previously screened for colorectal neoplasms. Differences in the prevalence of occult polyps in various populations might help explain the discordant reported sensitivities for polyp detection in published reports of CTC.

SUBJECTS AND METHODS

Seventy-five consecutive patients who had been previously screened for polyps underwent same-day colonoscopy and CTC. Many of the patients had personal histories of previous polypectomies and were undergoing surveillance colonoscopy. The scans were interpreted prospectively by an experienced radiologist. Polyps missed prospectively on CTC were analyzed retrospectively by three experienced radiologists and categorized as perception errors (visible in retrospect), technical errors (e.g., obscured by feces or fluid), or occult (invisible).

RESULTS

Thirty polyps 5 mm or larger were found at colonoscopy, 18 of which were missed prospectively on CTC. Of the 18 missed polyps, 12 could not be identified in retrospect, even though they were located in clean, dry, well-distended colonic segments. These were classified as occult. Ten of the 12 occult polyps showed flat morphology on review of colonoscopy video recordings. Of the remaining six missed polyps, two were classified as perception errors, two as technical errors, and two as a combination of technical and perception error.

CONCLUSION

In this population, colonographically occult polyps were common and accounted for more detection failures than perception errors and technical errors combined. The high prevalence of occult polyps may be explained by the fact that previous screening may have led to removal of easy-to-see polyps, creating a study population with a higher percentage of hard-to-see polyps.

Effective screening for bowel cancer: a United kingdom perspective

Bowel cancer is a major cause of morbidity and death and is a high cost to health care systems. Screening currently offers the best chance of improving outcomes from bowel cancer. When introducing screening, the problems encountered in other cancers need to be avoided to maximize benefits and minimize harms.

Virtual computed tomography cystoscopy in bladder pathologies

OBJECTIVE

Assessed the usefulness of virtual cystoscopy performed with multidetector computed tomography (CT) in patients with different urinary bladder pathologies compared to the conventional cystoscopy.

MATERIALS AND METHODS

Eighteen patients with different bladder pathologies, which consisted of 11 tumors, 3 diverticula, 2 trabecular changes and 2 stones, were assessed with conventional cystoscopy and virtual CT cystoscopy. The results of virtual CT cystoscopy were compared with the findings of conventional cystoscopy. We determined the detection rate and positive predictive value of CT imaging based virtual cystoscopy in the diagnosis of urinary bladder lesions.

RESULTS

CT scanning was well tolerated by all patients, and no complications occurred. Images in 16 (88%) of the 18 virtual cystoscopic examinations were either of excellent or good quality. All tumors except one, 2 trabecular changes and 2 stones were characterized with similar findings in the both of methods. The masses ranged from 0.4 to 7.0 cm in diameter. While conventional cystoscopy could not evaluate interior part of the diverticulum, virtual CT cystoscopy could demonstrate clearly within it. There were no false-positive findings in our series.

CONCLUSION

Virtual CT cystoscopy is a promising technique to be used in the detection of bladder lesions. It should be considered especially at the evaluation of bladder diverticula. In the future, it may be possible or even advantageous to incorporate into the imaging algorithm for evaluation of bladder lesion.