Computed tomographic virtual colonoscopy to screen for colorectal neoplasia in asymptomatic adults

CT Colonography: an update on current and future indications

Computed tomographic colonography (CTC) is a minimally invasive, patient-friendly, safe and robust colonic imaging modality. The technique is standardized and consolidated evidence from the literature shows that the diagnostic performances for the detection of colorectal cancer and large polyps are similar to colonoscopy (CS) and largely superior to alternative radiological exams, like barium enema. A clear understanding of the exact role of CTC will be beneficial to maximize the benefits and minimize the potential sources of frustration or disappointment for both referring clinicians and patients. Incomplete, failed, or unfeasible CS; investigation of elderly, and frail patients and assessment of diverticular disease are major indications supported by evidence-based data and agreed by the endoscopists. The use of CTC for symptomatic patients, colorectal cancer screening and colonic surveillance is still under debate and, thus, recommended only if CS is unfeasible or refused by patients.

Virtual Colonoscopy in Colorectal Cancer Screening

Colorectal cancer is the third most commonly diagnosed tumor in both males and females in the United States. Current modalities for colorectal cancer screening include fecal occult blood testing, flexible sigmoidoscopy, double-contrast barium enema, and colonoscopy. Virtual colonoscopy is a promising new method for assessing the entire colon. Vining and Gelfand first described this technique in 1994. Since then, virtual colonoscopy has been shown to be extremely safe and well tolerated by patients. Indications for virtual colonoscopy include screening for polyps, incomplete or failed colonoscopy, and preoperative assessment of the colon proximal to an occlusive cancer or even redundant fixed or stenotic colon that cannot be endoscopically traversed. Virtual colonoscopy may dramatically increase patient participation in screening programs, leading to early diagnosis of colorectal cancer. Although virtual colonoscopy seems a potentially attractive screening method for colorectal cancer, the cost-effectiveness of this method is yet to be determined.

Whole-body MRI in patients with lymphoma: collateral findings

PURPOSE

To assess the incidence of collateral findings detected on whole-body magnetic resonance (WB-MRI) scans performed on patients with lymphoma.

MATERIALS AND METHODS

114 patients (65 male; median age 45.2 years, range 15-86) with histologically confirmed lymphoma (47 Hodgkin, 67 Non-Hodgkin) underwent WB-MRI. The collateral findings were classified into three classes, according to their clinical significance, as follows: not or low significant (class 1), moderately or potentially significant (class 2), and significant (class 3). A Chi-square (χ (2)) test was performed to assess the statistical significance of differences in the incidence of collateral findings based on age (≤50 and >50 years old), gender and histology (Hodgkin and Non-Hodgkin Lymphoma).

RESULTS

Ninety-one of 114 patients (79.8 %) had one or more incidental findings on WB-MRI. Collateral findings were more frequent in class 1 (43 %); abnormalities found in 35 patients (30.7 %) were considered potentially significant, whereas seven patients (6.1 %) demonstrated significant collateral findings requiring immediate treatment or further diagnostic evaluation. Collateral findings were more frequent in subjects over 50 years old compared to those of 50 years old or younger; differences were statistical significant (χ (2) = 8.42, p < 0.05). There were not statistically significant differences related to gender (χ (2) = 0.17, p > 0.05) and histology (χ (2) = 0.24, p > 0.05).

CONCLUSION

WB-MRI is an attractive procedure that allows to detect incidental abnormalities of organs not involved by disease offering the opportunity to obtain an early diagnosis of asymptomatic life-threatening diseases.

Patient experience of CT colonography and colonoscopy after fecal occult blood test in a national screening programme

OBJECTIVE

To investigate patient experience of CT colonography (CTC) and colonoscopy in a national screening programme.

METHODS

Retrospective analysis of patient experience postal questionnaires. We included screenees from a fecal occult blood test (FOBt) based screening programme, where CTC was performed when colonoscopy was incomplete or deemed unsuitable. We analyzed questionnaire responses concerning communication of test risks, test-related discomfort and post-test pain, as well as complications. CTC and colonoscopy responses were compared using multilevel logistic regression.

RESULTS

Of 67,114 subjects identified, 52,805 (79 %) responded. Understanding of test risks was lower for CTC (1712/1970 = 86.9 %) than colonoscopy (48783/50975 = 95.7 %, p < 0.0001). Overall, a slightly greater proportion of screenees found CTC unexpectedly uncomfortable (506/1970 = 25.7 %) than colonoscopy (10,705/50,975 = 21.0 %, p < 0.0001). CTC was tolerated well as a completion procedure for failed colonoscopy (unexpected discomfort; CTC = 26.3 %: colonoscopy = 57.0 %, p < 0.001). Post-procedural pain was equally common (CTC: 288/1970,14.6 %, colonoscopy: 7544/50,975,14.8 %; p = 0.55). Adverse event rates were similar in both groups (CTC: 20/2947 = 1.2 %; colonoscopy: 683/64,312 = 1.1 %), but generally less serious with CTC.

CONCLUSIONS

Even though CTC was reserved for individuals either unsuitable for or unable to complete colonoscopy, we found only small differences in test-related discomfort. CTC was well tolerated as a completion procedure and was extremely safe. CTC can be delivered across a national screening programme with high patient satisfaction.

KEY POINTS

• High patient satisfaction at CTC is deliverable across a national screening programme. • Patients who cannot tolerate screening colonoscopy are likely to find CTC acceptable. • CTC is extremely safe; complications are rare and almost never serious. • Patients may require more detailed information regarding the expected discomfort of CTC.

Multi-Target Stool DNA Test: Is the Future Here?

Colorectal cancer (CRC) screening reduces CRC incidence and mortality and is widely recommended. However, despite these demonstrated benefits, a large percentage of the population remains unscreened. The multi-target stool DNA (MT-sDNA) test is a new, non-invasive option for CRC screening that has a high accuracy rate in detection of colorectal neoplasia and offers great opportunity to enhance screening uptake. This review provides the current state of the art knowledge about the use of MT-sDNA in CRC screening.

Symptomatic Versus Asymptomatic Colorectal Cancer: Predictive Features at CT Colonography

RATIONALE AND OBJECTIVES

Computed tomographic colonography (CTC) is a robust tool for evaluating colorectal lesions in both screening and diagnostic settings. The purpose of this study was to assess the relationship between colorectal cancer (CRC) tumor characteristics and patient symptomatology.

MATERIALS AND METHODS

This is a retrospective analysis of all pathology-confirmed cases of CRC evaluated with CTC at our institution from October 2004 to October 2012. Cases were reviewed to determine tumor size, morphology, and degree of luminal narrowing. An electronic medical record review was performed to delineate specific patient symptomatology and determine depth of invasion.

RESULTS

A total of 55 patients (36 symptomatic and 19 asymptomatic) with a total of 63 CRCs were evaluated by CTC during the study time period. The most common symptoms were gastrointestinal (GI) bleeding/anemia (n = 26), followed by obstructive symptoms (n = 23), and constitutional symptoms (n = 5). Symptomatic cancers were more likely to have annular morphology (n = 30/43, 70% vs. n = 3/20, 15%; odds ratio [OR] = 13.1, P = 0.0003), whereas asymptomatic cancers were more likely to be polypoid (n = 11/20, 55% vs. n = 6/43, 14%, OR = 7.5, P = 0.001). Symptomatic cancers were also larger (46.1 ± 22.4 vs. 38.8 ± 18.4 mm, P = 0.005) and resulted in greater luminal narrowing (8.7 ± 8.5 mm vs. 35.8 ± 18.8 mm, P < 0.0001) with deeper invasion (n = 29/35 [invasion unknown for 8 cases], 83% vs. n = 6/20, 30%, OR = 11.3, P = 0.0003). Invasive cancers were more likely to have annular morphology (66%, 23/25, P = 0.002).

CONCLUSIONS

There is an intuitive and predictable relationship between tumor characteristics on CTC and patient symptoms. Annular morphology, tumor size, degree of luminal narrowing, and invasive disease all correlate with the presence of symptoms.

Texture Feature Extraction and Analysis for Polyp Differentiation via Computed Tomography Colonography

Image textures in computed tomography colonography (CTC) have great potential for differentiating non-neoplastic from neoplastic polyps and thus can advance the current CTC detection-only paradigm to a new level with diagnostic capability. However, image textures are frequently compromised, particularly in low-dose CT imaging. Furthermore, texture feature extraction may vary, depending on the polyp spatial orientation variation, resulting in variable results. To address these issues, this study proposes an adaptive approach to extract and analyze the texture features for polyp differentiation. Firstly, derivative (e.g. gradient and curvature) operations are performed on the CT intensity image to amplify the textures with adequate noise control. Then Haralick co-occurrence matrix (CM) is used to calculate texture measures along each of the 13 directions (defined by the first and second order image voxel neighbors) through the polyp volume in the intensity, gradient and curvature images. Instead of taking the mean and range of each CM measure over the 13 directions as the so-called Haralick texture features, Karhunen-Loeve transform is performed to map the 13 directions into an orthogonal coordinate system so that the resulted texture features are less dependent on the polyp orientation variation. These simple ideas for amplifying textures and stabilizing spatial variation demonstrated a significant impact for the differentiating task by experiments using 384 polyp datasets, of which 52 are non-neoplastic polyps and the rest are neoplastic polyps. By the merit of area under the curve of receiver operating characteristic, the innovative ideas achieved differentiation capability of 0.8016, indicating the CTC diagnostic feasibility.

Diagnostics and Epidemiology of Colorectal Cancer

Colorectal cancer is one of the leading causes of cancer-related morbidity and mortality. Main risk factors include advanced age, family history, male sex, and lifestyle factors. Screening can reduce incidence and death from colorectal cancer. Therefore, prevention and early detection are crucial in order to detect and remove pre-neoplastic adenomas and to detect cancers at early stages. Colonoscopy, flexible sigmoidoscopy, and fecal occult blood tests are established tools for screening. Newer fecal immunochemical tests reveal higher sensitivities for advanced adenoma and cancer than guaiac-based hemoccult tests. Molecular stool and blood tests as well as virtual colonoscopy and colon capsule endoscopy are promising new developments so far not established as routine instruments for the prevention and early detection of colorectal cancer. Colonoscopy is the method of choice for the diagnosis of colorectal cancer and for adenoma removal. Prognosis is essentially dependent on the tumor stage at the time of the initial diagnosis. Proper staging based on imaging prior to therapy is a prerequisite. In rectal cancer, local staging is an essential requirement for the identification of appropriate candidates for neoadjuvant therapy.

Diagnostic value of computed tomography colonography (CTC) after incomplete optical colonoscopy

INTRODUCTION

This study evaluated the role of computed tomography colonography (CTC) in patients who previously underwent incomplete optical colonoscopy (OC). We analyzed the impact of colonic lesions in intestinal segments not studied by OC and extracolonic findings in these patients.

METHODS

Between January 2014 and May 2015, 61 patients with a history of abdominal pain and incomplete OC examination were studied by CTC. CTCs were performed by 320-row CT scan in both the supine and the prone position, without intravenous administration of contrast medium. In all patients both colonic findings and extracolonic findings were evaluated.

RESULTS

Among the study group, 24 CTC examinations were negative for both colonic and extracolonic findings while 6 examinations revealed the presence of both colonic and extracolonic findings. In 24 patients CTC depicted colonic anomalies without extracolonic ones, while in 7 patients it showed extracolonic findings without colonic ones.

DISCUSSION

CTC is a noninvasive imaging technique with the advantages of high diagnostic performance, rapid data acquisition, minimal patient discomfort, lack of need for sedation, and virtually no recovery time. CTC accurately allows the evaluation of the nonvisualized part of the colon after incomplete OC and has the distinct advantage to detect clinically important extracolonic findings in patients with incomplete OC potentially explaining the patient's symptoms and conditioning their therapeutic management.

CONCLUSION

CTC accurately allows the assessment of both colonic and extracolonic pathologies representing a useful diagnostic tool in patients for whom complete OC is not achievable.

Computed tomography colonography for the practicing radiologist: A review of current recommendations on methodology and clinical indications

Colorectal cancer (CRC) represents one of the most relevant causes of morbidity and mortality in Western societies. CRC screening is actually based on faecal occult blood testing, and optical colonoscopy still remains the gold standard screening test for cancer detection. However, computed tomography colonography (CT colonography) constitutes a reliable, minimally-invasive method to rapidly and effectively evaluate the entire colon for clinically relevant lesions. Furthermore, even if the benefits of its employment in CRC mass screening have not fully established yet, CT colonography may represent a reasonable alternative screening test in patients who cannot undergo or refuse colonoscopy. Therefore, the purpose of our review is to illustrate the most updated recommendations on methodology and the current clinical indications of CT colonography, according to the data of the existing relevant literature.

Comparison of 64-Detector CT Colonography and Conventional Colonoscopy in the Detection of Colorectal Lesions

Background:

Colon cancer is a leading cause of morbidity and mortality in developed countries. The early detection of colorectal cancer using screening programs is important for managing early-stage colorectal cancers and polyps. Modalities that allow examination of the entire colon are conventional colonoscopy, double contrast barium enema examination and multi-detector computed tomography (MDCT) colonography.

Objectives:

To compare CT colonography and conventional colonoscopy results and to evaluate the accuracy of CT colonography for detecting colorectal lesions.

Patients and Methods:

In a prospective study performed at Gastroenterology and Radiology Departments of Medical Faculty of Eskisehir Osmangazi University, CT colonography and colonoscopy results of 31 patients with family history of colorectal carcinoma, personal or family history of colorectal polyps, lower gastrointestinal tract bleeding, change in bowel habits, iron deficiency anemia and abdominal pain were compared. Regardless of the size, CT colonography and conventional colonoscopy findings for all the lesions were cross - tabulated and the sensitivity, specificity, and positive and negative predictive values were calculated. To assess the agreement between CT colonography and conventional colonoscopy examinations, the Kappa coefficient of agreementt was used. Statistical analysis was performed by SPSS ver 15.0.

Results:

Regardless of the size, MDCT colonography showed 83% sensitivity and 95% specificity, with a positive predictive value of 95% and a negative predictive value of 83% for the detection of colorectal polyps and masses. MDCT colonography displayed 92% sensitivity and 95% specificity, with a positive predictive value of 92% and a negative predictive value of 95% for polyps ≥ 10 mm. For polyps between 6mm and 9 mm, MDCT colonography displayed 75% sensitivity and 100% specificity, with a positive predictive value of 100% and a negative predictive value of 90%. For polyps ≤ 5 mm MDCT colonography displayed 88% sensitivity and 100% specificity with a positive predictive value of 100% and a negative predictive value of 95%.

Conclusions:

CT colonography is a safe and minimally invasive technique, a valuable diagnostic tool for examining the entire colon and a good alternative compared to other colorectal cancer screening tests because of its high sensitivity values in colorectal lesions over 1 cm.

The 100 most influential manuscripts in colorectal cancer: A bibliometric analysis

PURPOSE

Bibliometric analysis highlights the key topics and studies which have led to the current understanding and treatment of a disease of interest. In this original article we analyze the 100 most cited manuscripts in the field of colorectal cancer (CRC).

MATERIALS AND METHODS

The Thomson Reuters Web of Science database with the search terms 'colorectal cancer,' 'colorectal cancer surgery,' 'colon cancer,' 'rectal cancer,' 'colorectal carcinoma,' 'colon carcinoma,' 'rectal carcinoma' and/or 'colonoscopy' was used to identify the manuscripts for the study. Only full length manuscripts were included. The 100 most cited papers were identified and further analyzed by topic, journal, author, year and institution. The journals' 5 year impact factor and Eigenfactor scores were recorded.

RESULTS

146,833 eligible papers were returned. Within the top 100 cited manuscripts, the most studied topic was genetics in CRC (n = 41), followed by chemotherapy (n = 20) and surgical management (n = 7). The most cited paper authored by Fearon et al. (7850 citations) focused on genetic models of tumorgenesis. The NEJM published the highest number of papers (n = 23 with 42,576 citations). The country and year with the greatest number of publications were the USA (n = 62) and 2004 (n = 13) respectively.

CONCLUSION

The most cited manuscripts highlighted in the current work describe the genetic, immunologic, basic science and surgical techniques that have resulted in the current understanding and treatment of CRC. The majority of these works were published in high impact journals and have been cited at least 900 times each reflecting their quality and influence. This work provides a reference of what could be considered as the most influential papers in CRC and serves as a reference for researchers and clinicians as to what makes a 'citable' paper.

Sub-milliSievert ultralow-dose CT colonography with iterative model reconstruction technique

Purpose. The purpose of this study was to evaluate the technical and diagnostic performance of sub-milliSievert ultralow-dose (ULD) CT colonograpy (CTC) in the detection of colonic and extracolonic lesions.

Materials and Methods. CTC with standard dose (SD) and ULD acquisitions of 64 matched patients, half of them with colonic findings, were reconstructed with filtered back projection (FBP), hybrid (HIR) and iterative model reconstruction techniques (IMR). Image noise in six colonic segments, in the left psoas muscle and aorta were measured. Image quality of the left adrenal gland and of the colon in the endoscopic and 2D view was rated on a five point Likert scale by two observers, who also completed the reading of CTC for colonic and extracolonic findings.

Results. The mean radiation dose estimate was 4.1 ± 1.4 mSv for SD and 0.86 ± 0.17 mSv for ULD for both positions (p < 0.0001). In ULD-IMR, SD-IMR and SD-HIR, the endoluminal noise was decreased in all colonic segments compared to SD-FBP (p < 0.001). There were 27 small (6–9 mm) and 17 large (≥10 mm) colonic lesions that were classified as sessile polyps (n = 38), flat lesions (n = 3), or as a mass (n = 3). Per patient sensitivity and specificity were 0.82 and 0.93 for ULD-FBP, 0.97 and 0.97 for ULD-HIR, 0.97 and 1.0 for ULD-IMR. Per polyp sensitivity was 0.84 for ULD-FBP, 0.98 for ULD-HIR, 0.98 for ULD-IMR. Significantly less extracolonic findings were detected in ULD-FBP and ULD-HIR, but in the E4 category by C-RADS (potentially important findings), the detection was similar.

Conclusion. Both HIR and IMR are suitable for sub-milliSievert ULD CTC without sacrificing diagnostic performance of the study.

Ultrasound virtual endoscopy: Polyp detection and reliability of measurement in an in vitro study with pig intestine specimens

AIM: To present our initial experience regarding the feasibility of ultrasound virtual endoscopy (USVE) and its measurement reliability for polyp detection in an in vitro study using pig intestine specimens.

METHODS: Six porcine intestine specimens containing 30 synthetic polyps underwent USVE, computed tomography colonography (CTC) and optical colonoscopy (OC) for polyp detection. The polyp measurement defined as the maximum polyp diameter on two-dimensional (2D) multiplanar reformatted (MPR) planes was obtained by USVE, and the absolute measurement error was analyzed using the direct measurement as the reference standard.

RESULTS: USVE detected 29 (96.7%) of 30 polyps, remaining a 7-mm one missed. There was one false-positive finding. Twenty-six (89.7%) of 29 reconstructed images were clearly depicted, while 29 (96.7%) of 30 polyps were displayed on CTC with one false-negative finding. In OC, all the polyps were detected. The intraclass correlation coefficient was 0.876 (95%CI: 0.745-0.940) for measurements obtained with USVE. The pooled absolute measurement errors ± the standard deviations of the depicted polyps with actual sizes ≤ 5 mm, 6-9 mm, and ≥ 10 mm were 1.9 ± 0.8 mm, 0.9 ± 1.2 mm, and 1.0 ± 1.4 mm, respectively.

CONCLUSION: USVE is reliable for polyp detection and measurement in in vitro study.

Objective and Subjective Intrapatient Comparison of Iohexol Versus Diatrizoate for Bowel Preparation Quality at CT Colonography

OBJECTIVE

The purpose of this study is to objectively and subjectively compare nonionic iohexol and ionic diatrizoate iodinated oral contrast agents as part of a cathartic bowel regimen within the same CT colonography (CTC) cohort, with otherwise identical preparations.

MATERIALS AND METHODS

In this retrospective study, 46 adults with no symptoms (mean age, 59.4 years; 26 men and 20 women) returning for follow-up CTC over a 9-month interval underwent the same bowel preparation with the exception of 75 mL of iohexol 350 in place of 60 mL of diatrizoate. All other preparation components (bisacodyl, magnesium citrate, and 2% barium) remained constant. Objective volumetric analysis of residual colonic fluid volume and fluid attenuation was performed. Additionally, two radiologists experienced with CTC who were blinded to the specific bowel preparation scored each of six colonic segments for adherent residual solid stool using a previously validated 4-point scale (0 for no stool; 1-3 for increasing residual stool). A paired t test was used for comparison of the cohorts.

RESULTS

No clear clinically meaningful difference was found between the two preparations on overall objective or subjective evaluation. The mean (± SD) residual fluid volume was 173 ± 126 mL with the iohexol preparation and 130 ± 79 mL with the diatrizoate preparation (p = 0.02). The mean total colonic stool score was 2.5 (0.42/segment) with iohexol and 2.3 (0.38/segment) with diatrizoate (p = 0.69). The mean fluid attenuation was higher with iohexol (849 ± 270 HU) compared with diatrizoate (732 ± 168 HU) (p = 0.03).

CONCLUSION

On the basis of this direct intrapatient comparison, we found that oral iohexol is a suitable alternative to diatrizoate for fluid tagging as part of a cathartic bowel preparation at CTC. Because this nonionic tagging agent is more palatable, less expensive, and likely safer than ionic diatrizoate, our CTC program now uses iohexol as the standard recommended regimen.

Unsuspected colorectal carcinoma on routine abdominopelvic computed tomography

Colorectal carcinoma is a common lethal disease with signs and symptoms that may be nonspecific. Computed tomography (CT) of the abdomen and pelvis with or without contrast is frequently performed for various general abdominal complaints, but unlike CT colonography, the large bowel may not be optimally prepared for evaluation. As such, careful and diligent assessment of the non-prepared colon in all CT images of the abdomen and pelvis is important, as it ensures that incidental colorectal malignancy is not missed, especially in older patients. This article gives an overview of multidetector CT imaging signs and subtle clues to aid in the diagnosis of colorectal carcinoma, as well as their pitfalls.

Do prevalence expectations affect patterns of visual search and decision-making in interpreting CT colonography endoluminal videos?

OBJECTIVE

To assess the effect of expected abnormality prevalence on visual search and decision-making in CT colonography (CTC).

METHODS

13 radiologists interpreted endoluminal CTC fly-throughs of the same group of 10 patient cases, 3 times each. Abnormality prevalence was fixed (50%), but readers were told, before viewing each group, that prevalence was either 20%, 50% or 80% in the population from which cases were drawn. Infrared visual search recording was used. Readers indicated seeing a polyp by clicking a mouse. Multilevel modelling quantified the effect of expected prevalence on outcomes.

RESULTS

Differences between expected prevalence were not statistically significant for time to first pursuit of the polyp (median 0.5 s, each prevalence), pursuit rate when no polyp was on screen (median 2.7 s(-1), each prevalence) or number of mouse clicks [mean 0.75/video (20% prevalence), 0.93 (50%), 0.97 (80%)]. There was weak evidence of increased tendency to look outside the central screen area at 80% prevalence and reduction in positive polyp identifications at 20% prevalence.

CONCLUSION

This study did not find a large effect of prevalence information on most visual search metrics or polyp identification in CTC. Further research is required to quantify effects at lower prevalence and in relation to secondary outcome measures.

ADVANCES IN KNOWLEDGE

Prevalence effects in evaluating CTC have not previously been assessed. In this study, providing expected prevalence information did not have a large effect on diagnostic decisions or patterns of visual search.

Surveillance of colonic polyps: Are we getting it right?

Colorectal cancer (CRC) is the third most commonly diagnosed cancer worldwide. The identification of colonic polyps can reduce CRC mortality through earlier diagnosis of cancers and the removal of polyps: the precursor lesion of CRC. Following the finding and removal of colonic polyps at an initial colonoscopy, some patients are at an increased risk of developing CRC in the future. This is the rationale for post-polypectomy surveillance colonoscopy. However, not all individuals found to have colonic adenomas have a risk of CRC higher than that of the general population. This review examines the literature on post-polypectomy surveillance including current international clinical guidelines. The potential benefits of surveillance procedures must be weighed against the burden of colonoscopy: resource use, the potential for patient discomfort, and the risk of complications. Therefore surveillance colonoscopy is best utilised in a selected group of individuals at a high risk of developing cancer. Further study is needed into the specific factors conferring higher risk as well as the efficacy of surveillance in mitigating this risk. Such evidence will better inform clinicians and patients of the relative benefits of colonoscopic surveillance for the individual. In addition, the decision to continue with surveillance must be informed by the changing profile of risks and benefits of further procedures with the patient’s advancing age.

Colonoscopy detects significantly more flat adenomas than 3-tesla magnetic resonance colonography: a pilot trial

BACKGROUND AND STUDY AIMS

Colorectal cancer (CRC) is one of the most common cancers worldwide, and several efforts have been made to reduce its occurrence or severity. Although colonoscopy is considered the gold standard in CRC prevention, it has its disadvantages: missed lesions, bleeding, and perforation. Furthermore, a high number of patients undergo this procedure even though no polyps are detected. Therefore, an initial screening examination may be warranted. Our aim was to compare the adenoma detection rate of magnetic resonance colonography (MRC) with that of optical colonoscopy.

PATIENTS AND METHODS

A total of 25 patients with an intermediate risk for CRC (17 men, 8 women; mean age 57.6, standard deviation 11) underwent MRC with a 3.0-tesla magnet, followed by colonoscopy. The endoscopist was initially blinded to the results of MRC and unblinded immediately after examining the distal rectum. Following endoscopic excision, the size, anatomical localization, and appearance of all polyps were described according to the Paris classification.

RESULTS

A total of 93 lesions were detected during colonoscopy. These included a malignant infiltration of the transverse colon due to gastric cancer in 1 patient, 28 adenomas in 10 patients, 19 hyperplastic polyps in 9 patients, and 45 non-neoplastic lesions. In 5 patients, no lesion was detected. MRC detected significantly fewer lesions: 1 adenoma (P = 0.001) and 1 hyperplastic polyp (P = 0.004). The malignant infiltration was seen with both modalities. Of the 28 adenomas, 23 (82 %) were 5 mm or smaller; only 4 adenomas 10 mm or larger (14 %) were detected.

CONCLUSION

MRC does not detect adenomas sufficiently independently of the location of the lesion. Even advanced lesions were missed. Therefore, colonoscopy should still be considered the current gold standard, even for diagnostic purposes.

The European Society of Gastrointestinal Endoscopy Quality Improvement Initiative: developing performance measures

The European Society of Gastrointestinal Endoscopy (ESGE) and United European Gastroenterology (UEG) have a vision to create a thriving community of endoscopy services across Europe, collaborating with each other to provide high quality, safe, accurate, patient-centered and accessible endoscopic care. Whilst the boundaries of what can be achieved by advanced endoscopy are continually expanding, we believe that one of the most fundamental steps to achieving our goal is to raise the quality of everyday endoscopy. The development of robust, consensus- and evidence-based key performance measures is the first step in this vision. ESGE and UEG have identified quality of endoscopy as a major priority. This paper explains the rationale behind the ESGE Quality Improvement Initiative and describes the processes that were followed. We recommend that all units develop mechanisms for audit and feedback of endoscopist and service performance using the ESGE performance measures that will be published in future issues of this journal over the next year. We urge all endoscopists and endoscopy services to prioritize quality and to ensure that these performance measures are implemented and monitored at a local level, so that we can provide the highest possible care for our patients.

Real-Time Characterization of Diminutive Colorectal Polyp Histology Using Narrow-Band Imaging: Implications for the Resect and Discard Strategy

BACKGROUND & AIMS

Narrow-band imaging (NBI) allows real-time histologic classification of colorectal polyps. We investigated whether endoscopists without prior training in NBI can achieve the following thresholds recommended by the American Society for Gastrointestinal Endoscopy: for diminutive colorectal polyps characterized with high confidence, a ≥90% negative predictive value for adenomas in the rectosigmoid and a ≥90% agreement in surveillance intervals.

METHODS

Twenty-six endoscopists from 2 tertiary care centers underwent standardized training in NBI interpretation. Endoscopists made real-time predictions of diminutive colorectal polyp histology and surveillance interval predictions based on NBI. Their performance was evaluated by comparing predicted with actual findings from histologic analysis. Multilevel logistic regression was used to assess predictors of performance. Cumulative summation analysis was used to characterize learning curves.

RESULTS

The endoscopists performed 1451 colonoscopies and made 3012 diminutive polyp predictions (74.3% high confidence) using NBI. They made 898 immediate post-procedure surveillance interval predictions. An additional 505 surveillance intervals were determined with histology input. The overall negative predictive value for high-confidence characterizations in the rectosigmoid was 94.7% (95% confidence interval: 92.6%-96.8%) and the surveillance interval agreement was 91.2% (95% confidence interval: 89.7%-92.7%). Overall, 97.0% of surveillance interval predictions would have brought patients back on time or early. High-confidence characterization was the strongest predictor of accuracy (odds ratio = 3.42; 95% confidence interval: 2.72-4.29; P < .001). Performance improved over time, however, according to cumulative summation analysis, only 7 participants (26.9%) identified adenomas with sufficient sensitivity such that further auditing is not required.

CONCLUSIONS

With standardized training, gastroenterologists without prior expertise in NBI were able to meet the negative predictive value and surveillance interval thresholds set forth by the American Society for Gastrointestinal Endoscopy. The majority of disagreement in surveillance interval brought patients back early. Performance improves with time, but most endoscopists will require ongoing auditing of performance. ClinicalTrials.gov ID NCT02441998.

Willingness to Pay for CT Colonography: A Survey of Patient Preferences

OBJECTIVE

CT colonography (CTC) has received mixed reviews both in the radiology literature and in clinical practice. CTC is less invasive than optical colonoscopy (OC), is better for identifying polyps, and does not require sedation. However, its cost-effectiveness has been called into question, and there is a residual need for OC if the CTC findings are positive. Some radiologists are hesitant to perform CTC because of the time-intensive nature of its interpretation. Results of willingness-to-pay surveys can be informative about preferences and value placed on intangibles. The purpose of this study was to use such a survey to elicit the preferences of radiologists about CTC versus OC.

SUBJECTS AND METHODS

A vignette was presented in which the insurer covered OC at no charge but required out-of-pocket payment for CTC. The strengths and weaknesses of OC and CTC were listed. The respondents were asked how much they would be willing to pay for CTC; for CTC with perfect sensitivity, specificity, and accuracy; and for CTC that required no bowel preparation.

RESULTS

Twenty-eight of 42 radiologists preferred OC to CTC. One radiologist was indifferent. Four radiologists would reverse their preference and choose CTC if it had 100% sensitivity. Sixteen radiologists said they would prefer CTC if it had 100% specificity. If CTC eliminated the need for bowel preparation, 57% would prefer it to OC. Thirty-one (74%) radiologists preferred perfect sensitivity to perfect specificity.

CONCLUSION

Despite the less invasive nature of CTC, most radiologists who responded to the survey preferred OC for colorectal cancer screening, mostly because of the definitive nature of OC due to the capability of immediate biopsy of suspicious lesions and the lack of requirement for a second round of bowel preparation.

Preferences and acceptance of colorectal cancer screening in Thailand

Colorectal cancer (CRC) is now common in Thailand with an increase in incidence over time. Health authorities are planning to implement a nationwide CRC screening program using fecal immunochemical test (FIT) as a primary screening tool. This study aimed to estimate preferences and acceptance of FIT and colonoscopy, explore factors influencing the acceptance, and investigate reasons behind choosing and rejecting to screen before the program was implemented. Patients aged 50-69, visiting the primary care unit during the study period, were invited to join this study. Patients with a history of cancer or past CRC screening were excluded. Face-to-face interviews were conducted. Subjects were informed about CRC and the screening tests: FIT and colonoscopy. Then, they were asked for their opinions regarding the screening. The total number of subjects was 437 (86.7% response rate). Fifty-eight percent were females. The median age was 58 years. FIT was accepted by 74.1% of subjects compared to 55.6% for colonoscopy. The acceptance of colonoscopy was associated with perceived susceptibility to CRC and family history of cancer. No symptoms, unwilling to screen, healthy, too busy and anxious about diagnosis were reasons for refusing to screen. FIT was preferred for its simplicity and non-invasiveness compared with colonoscopy. Those rejecting FIT expressed a strong preference for colonoscopy. Subjects chose colonoscopy because of its accuracy; it was refused for the process and complications. If the screening program is implemented for the entire target population in Thailand, we estimate that 106,546 will have a positive FIT, between 8,618 and 12,749 identified with advanced adenoma and between 2,645 and 3,912 identified with CRC in the first round of the program.

CT colonography after incomplete optical colonoscopy: bowel preparation quality at same-day vs. deferred examination

PURPOSE

To objectively compare the volume, density, and distribution of luminal fluid for same-day oral-contrast-enhanced CTC following incomplete optical colonoscopy (OC) vs. deferred CTC on a separate day utilizing a dedicated CTC bowel preparation.

METHODS

HIPAA-compliant, IRB-approved retrospective study compared 103 same-day CTC studies after incomplete OC (utilizing 30 mL oral diatrizoate) against 151 CTC examinations performed on a separate day after failed OC using a dedicated CTC bowel preparation (oral magnesium citrate/dilute barium/diatrizoate the evening before). A subgroup of 15 patients who had both same-day CTC and separate-day routine CTC was also identified and underwent separate analysis. CTC exams were analyzed for opacified fluid distribution within the GI tract, as well as density and volume. Data were analyzed utilizing Kruskal-Wallis and Wilcoxon Signed Rank tests.

RESULTS

Opacified luminal fluid extended to the rectum in 56% (58/103) of same-day CTC vs. 100% (151/151) of deferred separate-day CTC (p < 0.0001). For same-day CTC, contrast failed to reach the colon in 11% (11/103) and failed to reach the left colon in 26% (27/103). Volumetric colonic fluid segmentation for fluid analysis (successful in 80 same-day and 147 separate-day cases) showed significantly more fluid in the same-day cohort (mean, 227 vs. 166 mL; p < 0.0001); the actual difference is underestimated due to excluded cases. Mean colonic fluid attenuation was significantly lower in the same-day cohort (545 vs. 735 HU; p < 0.0001). Similar findings were identified in the smaller cohort with direct intra-patient CTC comparison.

CONCLUSIONS

Dedicated CTC bowel preparation on a separate day following incomplete OC results in a much higher quality examination compared with same-day CTC.

Predictors of incomplete optical colonoscopy using computed tomographic colonography

BACKGROUND/AIMS

Optical colonoscopy (OC) is the primary modality for investigation of colonic pathology. Although there is data on demographic factors for incomplete OC, paucity of data exists for anatomic variables that are associated with an incomplete OC. These anatomic variables can be visualized using computed tomographic colonography (CTC). We aim to retrospectively identify variables associated with incomplete OC using CTC and develop a scoring method to predict the outcome of OC.

PATIENTS AND METHODS

In this case-control study, 70 cases ( with incomplete OC) and 70 controls (with complete OC) were identified. CTC images of cases and controls were independently reviewed by a single CTC radiologist. Demographic and anatomical parameters were recorded. Data was examined using descriptive linear statistics and multivariate logistic regression model.

RESULTS

On analysis, female gender (80% vs 58.6% P = 0.007), prior abdominal/pelvic surgeries (51.4% vs 14.3% P < 0.001), colonic length (187.6 ± 30.0 cm vs 163.8 ± 27.2 cm P < 0.001), and number of flexures (11.4 ± 3.1 vs 8.4 ± 2.9 P < 0.001) increased the risk for incomplete OC. No significant association was observed for increasing age (P = 0.881) and history of severe diverticulosis (P = 0.867) with incomplete OC. A scoring system to predict the outcome of OC is proposed based on CTC findings.

CONCLUSION

Female gender, prior surgery, and increasing colonic length and tortuosity were associated with incomplete OC, whereas increasing age and history of severe diverticulosis were not. These factors may be used in the future to predict those patients who are at risk of incomplete OC.

Quantitative radiology: automated measurement of polyp volume in computed tomography colonography using Hessian matrix-based shape extraction and volume growing

BACKGROUND

Current measurement of the single longest dimension of a polyp is subjective and has variations among radiologists. Our purpose was to develop a computerized measurement of polyp volume in computed tomography colonography (CTC).

METHODS

We developed a 3D automated scheme for measuring polyp volume at CTC. Our scheme consisted of segmentation of colon wall to confine polyp segmentation to the colon wall, extraction of a highly polyp-like seed region based on the Hessian matrix, a 3D volume growing technique under the minimum surface expansion criterion for segmentation of polyps, and sub-voxel refinement and surface smoothing for obtaining a smooth polyp surface. Our database consisted of 30 polyp views (15 polyps) in CTC scans from 13 patients. Each patient was scanned in the supine and prone positions. Polyp sizes measured in optical colonoscopy (OC) ranged from 6-18 mm with a mean of 10 mm. A radiologist outlined polyps in each slice and calculated volumes by summation of volumes in each slice. The measurement study was repeated 3 times at least 1 week apart for minimizing a memory effect bias. We used the mean volume of the three studies as "gold standard".

RESULTS

Our measurement scheme yielded a mean polyp volume of 0.38 cc (range, 0.15-1.24 cc), whereas a mean "gold standard" manual volume was 0.40 cc (range, 0.15-1.08 cc). The "gold-standard" manual and computer volumetric reached excellent agreement (intra-class correlation coefficient =0.80), with no statistically significant difference [P (F≤f) =0.42].

CONCLUSIONS

We developed an automated scheme for measuring polyp volume at CTC based on Hessian matrix-based shape extraction and volume growing. Polyp volumes obtained by our automated scheme agreed excellently with "gold standard" manual volumes. Our fully automated scheme can efficiently provide accurate polyp volumes for radiologists; thus, it would help radiologists improve the accuracy and efficiency of polyp volume measurements in CTC.

Patient Preferences Regarding Colorectal Cancer Screening: Test Features and Cost Willing to Pay Out of Pocket

The purpose of this investigation was to evaluate whether test features would make an individual more or less likely to undergo colorectal cancer screening and how much an individual would be willing to pay out of pocket for a screening test. The methods include an administration of a survey to consecutive adult patients of a general medicine clinic. The survey consisted of Likert-scale questions assessing the patients' likelihood of choosing a screening test based on various test characteristics. Additional questions measured the patients' age, race, gender, and maximum out-of-pocket cost they would be willing to pay. Chi-square tests were used to assess the associations between the likelihood questions and the various demographic characteristics. In results, survey response rate was 88.8% (213 of 240). Respondents were 48.4% female (103 of 213), 51.6% male (110 of 213), 82.6% White (176 of 213), 11.3% African-American (24 of 213), and 6.1% other (13 of 213). Risk of internal injury and light exposure to radiation were the least desirable test features. Light sedation was the only test feature that most respondents (54.8%) indicated would make them likely or very likely to undergo a colorectal cancer screening test. The vast majority of respondents (86.8%) were willing to pay less than $200 out of pocket for a colorectal cancer screening test. There was no statistically significant difference in the responses of males and females, or in the responses of individuals of different races or different ages regarding test features, or the amount individuals were willing to pay for a screening test. To conclude, survey results suggest that patient education emphasizing the low complication rate of computed tomographic colonography (CTC), the minimal risks associated with the low-level radiation exposure resulting from CTC, and the benefits of a sedation-free test (eg, no risk of sedation-related complication and no need for a driver) may increase patient acceptance of CTC. Additionally, an out-of-pocket cost of <$200 would be preferable from the patient perspective.

European Code against Cancer, 4th Edition: Cancer screening

In order to update the previous version of the European Code against Cancer and formulate evidence-based recommendations, a systematic search of the literature was performed according to the methodology agreed by the Code Working Groups. Based on the review, the 4th edition of the European Code against Cancer recommends: "Take part in organized cancer screening programmes for: Bowel cancer (men and women); Breast cancer (women); Cervical cancer (women)." Organized screening programs are preferable because they provide better conditions to ensure that the Guidelines for Quality Assurance in Screening are followed in order to achieve the greatest benefit with the least harm. Screening is recommended only for those cancers where a demonstrated life-saving effect substantially outweighs the potential harm of examining very large numbers of people who may otherwise never have, or suffer from, these cancers, and when an adequate quality of the screening is achieved. EU citizens are recommended to participate in cancer screening each time an invitation from the national or regional screening program is received and after having read the information materials provided and carefully considered the potential benefits and harms of screening. Screening programs in the European Union vary with respect to the age groups invited and to the interval between invitations, depending on each country's cancer burden, local resources, and the type of screening test used For colorectal cancer, most programs in the EU invite men and women starting at the age of 50-60 years, and from then on every 2 years if the screening test is the guaiac-based fecal occult blood test or fecal immunochemical test, or every 10 years or more if the screening test is flexible sigmoidoscopy or total colonoscopy. Most programs continue sending invitations to screening up to the age of 70-75 years. For breast cancer, most programs in the EU invite women starting at the age of 50 years, and not before the age of 40 years, and from then on every 2 years until the age of 70-75 years. For cervical cancer, if cytology (Pap) testing is used for screening, most programs in the EU invite women starting at the age of 25-30 years and from then on every 3 or 5 years. If human papillomavirus testing is used for screening, most women are invited starting at the age of 35 years (usually not before age 30 years) and from then on every 5 years or more. Irrespective of the test used, women continue participating in screening until the age of 60 or 65 years, and continue beyond this age unless the most recent test results are normal.

Methylation pattern of ALX4 gene promoter as a potential biomarker for blood-based early detection of colorectal cancer

BACKGROUND

To develop a non-invasive screening method for colorectal cancer, we evaluated the methylation of ALX4 gene promoter in serum samples from patients with colorectal cancer (CRC) and equal number of healthy individuals.

MATERIALS AND METHODS

In serum samples from 25 patients with colorectal cancer and 25 healthy control subjects, isolated serum free-floating DNA was treated with sodium bisulfite and analyzed by methylation-specific polymerase chain reaction (MSP) with primers specific for methylated or unmethylated promoter CpG island sequences of the ALX4 gene.

RESULTS

Methylation of the ALX4 gene promoter was present in the serum DNA of patients with adenoma and colorectal cancer. A sensitivity of 68% and specificity of 88% were achieved in the detection of promoter methylation in colorectal neoplasia samples. The difference in methylation status of the ALX4 promoter between the patients with colorectal neoplasia and the control group was statistically highly significant (P < 0.001).

CONCLUSIONS

The results indicate that this serum free DNA test of methylation of the ALX4 gene promoter is a sensitive and specific method. Therefore in combination with other useful markers it seems ALX4 has the potential of a clinically useful test for the early detection of colorectal cancer.

CT colonography with computer-aided detection: recognizing the causes of false-positive reader results

Computed tomography (CT) colonography is a screening modality used to detect colonic polyps before they progress to colorectal cancer. Computer-aided detection (CAD) is designed to decrease errors of detection by finding and displaying polyp candidates for evaluation by the reader. CT colonography CAD false-positive results are common and have numerous causes. The relative frequency of CAD false-positive results and their effect on reader performance on the basis of a 19-reader, 100-case trial shows that the vast majority of CAD false-positive results were dismissed by readers. Many CAD false-positive results are easily disregarded, including those that result from coarse mucosa, reconstruction, peristalsis, motion, streak artifacts, diverticulum, rectal tubes, and lipomas. CAD false-positive results caused by haustral folds, extracolonic candidates, diminutive lesions (<6 mm), anal papillae, internal hemorrhoids, varices, extrinsic compression, and flexural pseudotumors are almost always recognized and disregarded. The ileocecal valve and tagged stool are common sources of CAD false-positive results associated with reader false-positive results. Nondismissable CAD soft-tissue polyp candidates larger than 6 mm are another common cause of reader false-positive results that may lead to further evaluation with follow-up CT colonography or optical colonoscopy. Strategies for correctly evaluating CAD polyp candidates are important to avoid pitfalls from common sources of CAD false-positive results.

Colorectal cancer screening in the familial risk population: Is colonoscopy still the strategy of choice?

First-degree relatives of patients with colorectal cancer (CRC) are at high risk of this disease. For this reason, medical organizations and clinical guidelines recommend more intensive screening and surveillance for such first-degree relatives than for the average-risk population. Colonoscopy has been the cornerstone of CRC screening in this setting. Although colonoscopy is the most sensitive technique for the detection of neoplastic lesions (especially non-advanced adenomas), its role is less clear for CRC. In addition, screening colonoscopy has several limitations that may affect the success of a screening campaign, such as poor participant acceptance, the need for skilled endoscopists, participant access to screening colonoscopy, overburdened endoscopy units, potential complications, and procedure-related costs. In addition, recent evidence has cast doubt on the advantage of colonoscopy over other strategies for the detection of advanced neoplastic lesions. Despite being less sensitive in general, other screening methods frequently recommended in the average-risk population may be more acceptable and thus help increase CRC screening uptake. This review discusses recent evidence on the risk of CRC in first-degree relatives, the advantages and disadvantages of each screening technique, participation rates depending on the technique, patient preferences, and barriers to screening.

Potentially Important Extracolonic Findings at Screening CT Colonography: Incidence and Outcomes Data From a Clinical Screening Program

OBJECTIVE

The effect of detection of extracolonic findings at screening CT colonography (CTC) remains controversial. Our objective is to analyze the incidence and outcomes of unsuspected potentially significant (CT Colonography Reporting and Data System [C-RADS] extracolonic category E4) findings in a population undergoing clinical CTC screening.

SUBJECTS AND METHODS

Over the course of 99 months (April 1, 2004, through June 30, 2012), 7952 consecutive asymptomatic adults (3675 men and 4277 women; mean [± SD] age, 56.7 ± 7.3 years) underwent first-time screening CTC. Examinations were prospectively interpreted by radiologists within our abdominal imaging section, and extracolonic findings were recorded and categorized. Potentially significant (i.e., C-RADS extracolonic category E4) findings were retrospectively reviewed with additional analysis of follow-up (range, 2-10 years) and ultimate clinical outcome.

RESULTS

Overall, 2.5% (202/7952) of patients had a potentially significant (C-RADS category E4) extracolonic finding for which further imaging (56%; 113/202) or clinical follow-up (44%; 89/202) was recommended. No patients had multiple category E4 findings. Twenty-two patients were lost to follow-up. Of the remaining 180 patients, 68% (123/180) proved to have clinically significant disease, including 23% (42/180) with malignant or potentially malignant neoplasms and 32% (57/180) with abdominal aortic or other visceral artery aneurysms requiring treatment or surveillance. The most commonly involved organs and systems included the vascular system (26%; 53/202), the genitourinary system (18%; 36/202), the liver (15%; 30/202), the gastrointestinal system (9.9%; 20/202), the lungs (9.4%; 19/202), and the gynecologic system (6.9%; 14/202).

CONCLUSION

Potentially significant extracolonic findings in asymptomatic adults at screening CTC are uncommon (2-3% of cases). However, most of these findings (68%) will prove to be clinically significant, including a number of malignancies and aneurysms requiring treatment or surveillance.

Objective volumetric comparison of room air versus carbon dioxide for colonic distention at screening CT colonography

PURPOSE

To objectively compare colonic distention at CT colonography (CTC) achieved with manual room air vs. automated low-pressure carbon dioxide (CO2) using a novel automated volumetric quality assessment tool.

METHODS

Volumetric analysis was retrospectively performed on CTC studies in 300 asymptomatic adults using an automated quality assessment tool (V3D Colon [beta version], Viatronix). Colonic distention was achieved with room air self-administered to tolerance via hand-held pump (mean number of pumps, 39 ± 32) in 150 individuals (mean age, 59 years; 98 men, 51 women) and via continuous low-pressure automated infusion of CO2 in 150 individuals (mean age, 57 years; 89 men, 61 women). CTC studies in supine and prone position were assessed to determine total colonic volume (luminal gas and fluid). The colonic length along the automated centerline was also recorded to enable calculation of length-adjusted colonic volumes.

RESULTS

The mean total colonic volume (±SD) for individuals receiving room air and CO2 distention was 1809 ± 514 and 2223 ± 686 mL, respectively (p < 0.01). The prone position was better distended in 78.7% (118/150) of cases using room air; whereas, the supine was better in 66.0% (99/150) of CO2 cases (p < 0.01). Using a volume threshold of 2000 mL, 49 (32.7%) of room air cases and 92 (61.3%) of CO2 cases were above this cut-off. The mean length-adjusted colonic volume (mL/cm) for the room air and CO2 techniques was 9.9 ± 2.4 and 11.6 ± 2.6 mL/cm (p < 0.01).

CONCLUSIONS

Using automated volumetry allowed quantitative analyses of colonic volumes and objectively confirmed that continuous low-pressure CO2 provides greater overall colonic distention than the manual room air technique at CTC. The supine position demonstrated better distention with CO2, whereas the prone position was better distended with the room air technique.

Developments in Screening Tests and Strategies for Colorectal Cancer

BACKGROUND

Worldwide, colorectal cancer (CRC) is the third most common cancer in men and second most common in women. It is the fourth most common cause of cancer mortality. In the United States, CRC is the third most common cause of cancer and second most common cause of cancer mortality. Incidence and mortality rates have steadily fallen, primarily due to widespread screening.

METHODS

We conducted keyword searches on PubMed in four categories of CRC screening: stool, endoscopic, radiologic, and serum, as well as news searches in Medscape and Google News.

RESULTS

Colonoscopy is the gold standard for CRC screening and the most common method in the United States. Technological improvements continue to be made, including the promising "third-eye retroscope." Fecal occult blood remains widely used, particularly outside the United States. The first at-home screen, a fecal DNA screen, has also recently been approved. Radiological methods are effective but seldom used due to cost and other factors. Serum tests are largely experimental, although at least one is moving closer to market.

CONCLUSIONS

Colonoscopy is likely to remain the most popular screening modality for the immediate future, although its shortcomings will continue to spur innovation in a variety of modalities.

Small Polyps at Endoluminal CT Colonography Are Often Seen But Ignored by Radiologists

OBJECTIVE

The objective of our study was to describe the characteristics of polyps viewed but then dismissed incorrectly by radiologists at endoluminal CT colonography (CTC), eye movements during these errors, and features provoking false-positive diagnoses.

MATERIALS AND METHODS

Forty-two radiologists viewed 30 endoluminal CTC videos, each depicting a polyp, while their eye movements were tracked. Half of the videos had computer-assisted detection (CAD), and half did not. Classification errors were defined when proven polyps were seen but dismissed. Eye movements during these errors and during correct polyp identifications were compared with multilevel modeling. Polyps were divided subsequently into "difficult to classify" and "easy to classify" using a classification error threshold of more than 15%. Polyp diameter, height, and subjective conspicuity and the proportion of time viewed were compared between groups.

RESULTS

Eye tracking revealed that 97% of false-negative polyp diagnoses were nonetheless preceded by the reader observing the polyp. The difficult polyps were significantly smaller than the easy polyps (mean diameter, 5.4 vs 8.2 mm, respectively p = 0.014) and were subjectively less conspicuous (median score, 4 vs 2; p = 0.0032). Readers spent proportionally less time viewing difficult polyps than viewing easy polyps (29.0% of the time they were on-screen vs 42.6%, respectively; p = 0.01) regardless of the presence of CAD.

CONCLUSION

Even small and subjectively inconspicuous polyps attract reader gaze, but they are nonetheless ignored. These errors are made rapidly even with CAD. Efforts to improve reader performance at CTC should focus on decision making rather than detection alone.

Colorectal cancer screening: a global overview of existing programmes

Colorectal cancer (CRC) ranks third among the most commonly diagnosed cancers worldwide, with wide geographical variation in incidence and mortality across the world. Despite proof that screening can decrease CRC incidence and mortality, CRC screening is only offered to a small proportion of the target population worldwide. Throughout the world there are widespread differences in CRC screening implementation status and strategy. Differences can be attributed to geographical variation in CRC incidence, economic resources, healthcare structure and infrastructure to support screening such as the ability to identify the target population at risk and cancer registry availability. This review highlights issues to consider when implementing a CRC screening programme and gives a worldwide overview of CRC burden and the current status of screening programmes, with focus on international differences.

Automated volumetric analysis for comparison of oral sulfate solution (SUPREP) with established cathartic agents at CT colonography

PURPOSE

To objectively compare residual colonic fluid volume and attenuation of oral sulfate solution (OSS) with four different established cathartic regimens using an automated volumetric software tool at CT colonography (CTC).

METHODS

This HIPAA-compliant study had institutional review board approval. Volumetric analysis of residual contrast-tagged colonic fluid was performed on CTC studies in 263 adults (mean age 60.1 years; 137M/126F) using an automated volumetric software tool. Twenty-three patients receiving 177 mL OSS (SUPREP; single-bottle purgation) were compared with 60 patients each receiving 45 mL sodium phosphate (NaP), 90 mL NaP (2× NaP), 592 mL (two bottles) magnesium citrate (MgC), and 4,000 mL polyethylene glycol (PEG). All patients received oral contrast cleansing after catharsis. Data were analyzed with unpaired t test with Welch correction and F test.

RESULTS

The mean volume of residual colonic fluid was less with OSS (125 ± 60 mL) than for established cathartic agents: 2× NaP (206 ± 125 mL, P < 0.0001), MgC (184 ± 125 mL, P < 0.01), PEG (166 ± 114 mL, P < 0.05), and NaP (165 ± 135 mL, P = 0.067). Variance of volumes was also significantly lower for OSS (range 28-251 mL) than for established agents (range 4-853 mL) (all P < 0.01). Mean fluid attenuation was higher with OSS (956 ± 168 HU) than for established agents (all P < 0.05): 2× NaP (455 ± 191 HU), MgC (691 ± 154 HU), NaP (779 ± 127 HU), and PEG (843 ± 193 HU).

CONCLUSIONS

Automated volumetry allows rapid objective assessment of bowel preparation quality at CTC. Purgation with the novel oral sulfate solution (SUPREP) consistently resulted in less residual colonic fluid and higher fluid attenuation compared with established cathartic regimens.

An adaptive paradigm for computer-aided detection of colonic polyps

Most previous efforts in developing computer-aided detection (CADe) of colonic polyps apply similar measures or parameters to detect polyps regardless of their locations under an implicit assumption that all the polyps reside in a similar local environment, e.g. on a relatively flat colon wall. In reality, this implicit assumption is frequently invalid, because the haustral folds can have a very different local environment from that of the relatively flat colon wall. We conjecture that this assumption may be a major cause of missing the detection of polyps, especially small polyps (<10 mm linear size) located on the haustral folds. In this paper, we take the concept of adaptiveness and present an adaptive paradigm for CADe of colonic polyps. Firstly, we decompose the complicated colon structure into two simplified sub-structures, each of which has similar properties, of (1) relatively flat colon wall and (2) ridge-shaped haustral folds. Then we develop local environment descriptions to adaptively reflect each of these two simplified sub-structures. To show the impact of the adaptiveness of the local environment descriptions upon the polyp detection task, we focus on the local geometrical measures of the volume data for both the detection of initial polyp candidates (IPCs) and the reduction of false positives (FPs) in the IPC pool. The experimental outcome using the local geometrical measures is very impressive such that not only the previously-missed small polyps on the folds are detected, but also the previously miss-removed small polyps on the folds during FP reduction are retained. It is expected that this adaptive paradigm will have a great impact on detecting the small polyps, measuring their volumes and volume changes over time, and optimizing their management plan.

Colorectal Polyps Missed with Optical Colonoscopy Despite Previous Detection and Localization with CT Colonography

PURPOSE

To retrospectively evaluate and characterize nondiminutive colorectal polyps prospectively detected by using computed tomographic (CT) colonography but not confirmed with subsequent nonblinded optical colonoscopy (OC).

MATERIALS AND METHODS

This study was institutional review board approved; the need for signed informed consent was waived. Over 113 months, 9336 adults (mean age, 57.1 years) underwent CT colonography, which yielded 2606 nondiminutive (≥6 mm) polyps. Of 1731 polyps that underwent subsequent nonblinded OC (ie, endoscopists provided advanced knowledge of specific polyp size, location, and morphologic appearance at CT colonography), 181 (10%) were not confirmed with initial endoscopy (ie, discordant), of which 37 were excluded (awaiting or lost to follow-up). After discordant polyp review, 66 of the 144 lesions were categorized as likely CT colonography false-positive findings (no further action) and 78 were categorized as potential OC false-negative (FN) findings.

RESULTS

Thirty-one of 144 (21.5%) of all discordant lesions were confirmed as FN findings at OC, including 40% (31 of 78) of those with OC and/or CT colonography follow-up. OC FN lesions were an average of 8.5 mm ± 3.3 in diameter and were identified with higher confidence at prospective CT colonography (on a 3-point confidence scale: mean, 2.8 vs 2.3; P = .001). OC FN findings were more likely than concordant polyps to be located in the right colon (respectively, 71% [22 of 31] vs 47% [723 of 1535]; P = .010). Most (81% [21 of 26]) OC FN lesions that were ultimately resected were neoplastic (adenomas or serrated lesions), of which 43% (nine of 21) were characterized as advanced lesions, and 89% (eight of nine) of advanced lesions occurred in the right colon.

CONCLUSION

In clinical practice, polyps prospectively identified with CT colonography but not confirmed with subsequent nonblinded (ie, despite a priori knowledge of the CT colonography findings) OC require additional review because a substantial proportion may be FN findings. Most FN findings found with OC demonstrated clinically significant histopathologic results, and a majority of advanced lesions occurred in the right colon.

Smart Colonography for Distributed Medical Databases with Group Kernel Feature Analysis

Computer-Aided Detection (CAD) of polyps in Computed Tomographic (CT) colonography is currently very limited since a single database at each hospital/institution doesn't provide sufficient data for training the CAD system's classification algorithm. To address this limitation, we propose to use multiple databases, (e.g., big data studies) to create multiple institution-wide databases using distributed computing technologies, which we call smart colonography. Smart colonography may be built by a larger colonography database networked through the participation of multiple institutions via distributed computing. The motivation herein is to create a distributed database that increases the detection accuracy of CAD diagnosis by covering many true-positive cases. Colonography data analysis is mutually accessible to increase the availability of resources so that the knowledge of radiologists is enhanced. In this article, we propose a scalable and efficient algorithm called Group Kernel Feature Analysis (GKFA), which can be applied to multiple cancer databases so that the overall performance of CAD is improved. The key idea behind the proposed GKFA method is to allow the feature space to be updated as the training proceeds with more data being fed from other institutions into the algorithm. Experimental results show that GKFA achieves very good classification accuracy.

The safety of same-day CT colonography following incomplete colonoscopy with polypectomy

BACKGROUND

Concerns about the risk of bowel perforation for same-day computed tomography colonography (CTC) following an incomplete colonoscopy with polypectomy may lead to unnecessarily postponing the CTC.

OBJECTIVE

The objective of this article is to describe the complications including colon perforations associated with same-day CTC in a cohort who had polypectomies but an incomplete colonoscopy.

DESIGN

We conducted a retrospective study.

SETTING

Our study took place in a single, tertiary referral center.

PATIENTS

We studied consecutive patients who had CTC the same day as an incomplete colonoscopy with polypectomy.

INTERVENTIONS

Interventions included optical colonoscopy (OC), endoscopic polypectomies, and same-day CTC.

MAIN OUTCOME MEASUREMENTS

Our main outcome measurements included perforation rate with long-term follow-up.

RESULTS

A total of 3% of patients undergoing colonoscopy from January 2008 to December 2012 had same-day CTC following incomplete OC, and 72 polypectomies were performed in 34 (or 17%) of these patients. Incomplete colonoscopies were due to colon tortuosity and looping (25), severe angulations (five), colon mass (two), colon stenosis (one), bradycardia (one). Fifty-three percent of the OCs were screening for colon neoplasia, 29% diagnostic and 18% were surveillance of colon polyps. Most polyps were ≤ 5 mm, and found in the left colon. There were no reported complications or perforations associated with same-day CTCs during short- and long-term follow-up.

LIMITATIONS

Limitations of our analysis included retrospective single-center design, small number of patients for the occurrence, referral to same-day CTC was not standardized, inability to establish safety of CTC for specific scenarios such as after complex polypectomies, strictures, or advanced IBD.

CONCLUSIONS

Radiologists' apprehension to perform a CTC the same day as an incomplete colonoscopy following polypectomies because of perceived risk of perforation may be unfounded. More data are needed to determine the safety of same-day CTC in patients with high-risk findings during colonoscopy such as a stricture, severe IBD, and after complex polypectomies.

Computed tomography-gastro-colonography for percutaneous endoscopic gastrostomy using a helical computed tomography

BACKGROUND

Despite the widespread use of percutaneous endoscopic gastrostomy (PEG) tubes, their placement may be associated with a variety of complications, including gastrocolic fistula.

METHODS

In total, 48 individuals underwent computed tomography-gastro-colonography (CT-GC)-guided PEG placement. Study end points included success of CT-GC, inability to thread the PEG tube, the eventual tube location, tube adjustments needed, adverse events, operating time, and PEG tube-related infection.

RESULTS

A successful CT-GC was achieved in all 48 patients (100%), and we successfully used a standard PEG technique to place the gastrostomy tube in 44 patients (92%). In 4 patients (8%), the laparoscopic-assisted PEG technique was used because the transverse colon became interposed between the abdominal wall and the anterior wall of the stomach. The overall procedure-related minor complication rate was 8%.

CONCLUSION

CT-GC is an optional method for the estimation of intra-abdominal, anatomical orientations that may minimize the risk of complications before PEG placement.

3D detection of colonic polyps by CT colonography: accuracy, pitfalls, and solutions by adjunct 2D workup

Computed tomography colonography (CTC) enables evaluation of the colon with minimal invasiveness. In spite of advances in multidetector CT (MDCT) technology and advanced software features, including electronic bowel cleansing (digital removal and tagging of fluid and debris), a number of potential pitfalls in the evaluation of the 3D volumetric dataset persist. The purpose of this article is to illustrate the strengths and potential pitfalls in the detection of colorectal polyps using CTC via a primary three-dimensional (3D) approach for evaluation.

Comprehensive Assessment of Osteoporosis and Bone Fragility with CT Colonography

PURPOSE

To evaluate the ability of additional analysis of computed tomographic (CT) colonography images to provide a comprehensive osteoporosis assessment.

MATERIALS AND METHODS

This Health Insurance Portability and Accountability Act-compliant study was approved by our institutional review board with a waiver of informed consent. Diagnosis of osteoporosis and assessment of fracture risk were compared between biomechanical CT analysis and dual-energy x-ray absorptiometry (DXA) in 136 women (age range, 43-92 years), each of whom underwent CT colonography and DXA within a 6-month period (between January 2008 and April 2010). Blinded to the DXA data, biomechanical CT analysis was retrospectively applied to CT images by using phantomless calibration and finite element analysis to measure bone mineral density and bone strength at the hip and spine. Regression, Bland-Altman, and reclassification analyses and paired t tests were used to compare results.

RESULTS

For bone mineral density T scores at the femoral neck, biomechanical CT analysis was highly correlated (R(2) = 0.84) with DXA, did not differ from DXA (P = .15, paired t test), and was able to identify osteoporosis (as defined by DXA), with 100% sensitivity in eight of eight patients (95% confidence interval [CI]: 67.6%, 100%) and 98.4% specificity in 126 of 128 patients (95% CI: 94.5%, 99.6%). Considering both the hip and spine, the classification of patients at high risk for fracture by biomechanical CT analysis--those with osteoporosis or "fragile bone strength"--agreed well against classifications for clinical osteoporosis by DXA (T score ≤-2.5 at the hip or spine), with 82.8% sensitivity in 24 of 29 patients (95% CI: 65.4%, 92.4%) and 85.7% specificity in 66 of 77 patients (95% CI: 76.2%, 91.8%).

CONCLUSION

Retrospective biomechanical CT analysis of CT colonography for colorectal cancer screening provides a comprehensive osteoporosis assessment without requiring changes in imaging protocols.

The role of virtual colonoscopy in colorectal screening

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.

Computer-aided detection of renal calculi from noncontrast CT images using TV-flow and MSER features

PURPOSE

Renal calculi are common extracolonic incidental findings on computed tomographic colonography (CTC). This work aims to develop a fully automated computer-aided diagnosis system to accurately detect renal calculi on CTC images.

METHODS

The authors developed a total variation (TV) flow method to reduce image noise within the kidneys while maintaining the characteristic appearance of renal calculi. Maximally stable extremal region (MSER) features were then calculated to robustly identify calculi candidates. Finally, the authors computed texture and shape features that were imported to support vector machines for calculus classification. The method was validated on a dataset of 192 patients and compared to a baseline approach that detects calculi by thresholding. The authors also compared their method with the detection approaches using anisotropic diffusion and nonsmoothing.

RESULTS

At a false positive rate of 8 per patient, the sensitivities of the new method and the baseline thresholding approach were 69% and 35% (p < 1e - 3) on all calculi from 1 to 433 mm(3) in the testing dataset. The sensitivities of the detection methods using anisotropic diffusion and nonsmoothing were 36% and 0%, respectively. The sensitivity of the new method increased to 90% if only larger and more clinically relevant calculi were considered.

CONCLUSIONS

Experimental results demonstrated that TV-flow and MSER features are efficient means to robustly and accurately detect renal calculi on low-dose, high noise CTC images. Thus, the proposed method can potentially improve diagnosis.