Assessing attitudes toward laxative preparation in colorectal cancer screening and effects on future testing: potential receptivity to computed tomographic colonography

Canadian Association of Radiologists Practice Guidelines for Computed Tomography Colonography

Colon cancer is the third most common malignancy in Canada. Computed tomography colonography (CTC) provides a creditable and validated option for colon screening and assessment of known pathology in patients for whom conventional colonoscopy is contraindicated or where patients self-select to use imaging as their primary modality for initial colonic assessment. This updated guideline aims to provide a toolkit for both experienced imagers (and technologists) and for those considering launching this examination in their practice. There is guidance for reporting, optimal exam preparation, tips for problem solving to attain high quality examinations in challenging scenarios as well as suggestions for ongoing maintenance of competence. We also provide insight into the role of artificial intelligence and the utility of CTC in tumour staging of colorectal cancer. The appendices provide more detailed guidance into bowel preparation and reporting templates as well as useful information on polyp stratification and management strategies. Reading this guideline should equip the reader with the knowledge base to perform colonography but also provide an unbiased overview of its role in colon screening compared with other screening options.

Effect of dose splitting of a low-volume bowel preparation macrogol-based solution on CT colonography tagging quality

Purpose

To compare examination quality and acceptability of three different low-volume bowel preparation regimens differing in scheduling of the oral administration of a Macrogol-based solution, in patients undergoing computed tomographic colonography (CTC). The secondary aim was to compare CTC quality according to anatomical and patient variables (dolichocolon, colonic diverticulosis, functional and secondary constipation).

Methods

One-hundred-eighty patients were randomized into one of three regimens where PEG was administered, respectively: in a single dose the day prior to (A), or in a fractionated dose 2 (B) and 3 days (C) before the examination. Two experienced radiologists evaluated fecal tagging (FT) density and homogeneity both qualitatively and quantitatively by assessing mean segment density (MSD) and relative standard deviation (RSD). Tolerance to the regimens and patient variables were also recorded.

Results

Compared to B and C, regimen A showed a lower percentage of segments with inadequate FT and a significantly higher median FT density and/or homogeneity scores as well as significantly higher MSD values in some colonic segments. No statistically significant differences were found in tolerance of the preparations. A higher number of inadequate segments were observed in patients with dolichocolon (p < 0.01) and secondary constipation (p < 0.01). Interobserver agreement was high for the assessment of both FT density (k = 0.887) and homogeneity (k = 0.852).

Conclusion

The best examination quality was obtained when PEG was administered the day before CTC in a single session. The presence of dolichocolon and secondary constipation represent a risk factor for the presence of inadequately tagged colonic segments.

Googling on Colonoscopy: A Retrospective Analysis of Search Engine Statistics

PURPOSE

Colonoscopy is a gold standard for screening and diagnosis of colorectal cancer (CRC). The data from the search engine may reveal what information on coloscopy gains the attention of Internet users. We aimed to investigate Google searches trends and terms related to colonoscopy.

PATIENTS AND METHODS

We retrieved statistics searches related to colonoscopy using Google Trends (GT) and Google Ads (GA) for the period from April 2016 to March 2020. The GT data was used for the analysis of time and regional search patterns worldwide. GA data for Australia, Canada, Ireland, New Zealand (NZ), Poland, the United Kingdom (UK), and the United States (US) were used to calculate the search volume of categories of queries related to colonoscopy.

RESULTS

Globally, the relative search volume on colonoscopy has increased until the COVID-19 outbreak and revealed seasonal variation: the highest interest was observed in March (CRC awareness month), and the lowest during December (Christmas holidays). The highest number of searches per 1000 Google users-years was done in Poland (59.62) and the lowest in the UK (19.46). Most commonly, Google users searched for details on colonoscopy techniques (Australia, Canada, Ireland, NZ), anesthesia during the procedure (Poland), facility performing colonoscopy (UK, US). In all seven countries, less than 2% of queries concerned with bowel preparation before the procedure.

CONCLUSION

Before the COVID-19 pandemic, the interest in colonoscopy has increased among Google users. Google users may underestimate the importance of proper bowel preparation.

Improved Sensitivity and Reader Confidence in CT Colonography Using Dual-Layer Spectral CT: A Phantom Study

Background Limited cathartic preparations for CT colonography with fecal tagging can improve patient comfort but may result in nondiagnostic examinations from poorly tagged stool. Dual-energy CT may overcome this limitation by improving the conspicuity of the contrast agent, but more data are needed. Purpose To investigate whether dual-energy CT improves polyp detection in CT colonography compared with conventional CT at different fecal tagging levels in vitro. Materials and Methods In this HIPAA-compliant study, between December 2017 and August 2019, a colon phantom 30 cm in diameter containing 60 polyps of different shapes (spherical, ellipsoid, flat) and size groups (5-9 mm, 11-15 mm) was constructed and serially filled with simulated feces tagged with four different iodine concentrations (1.26, 2.45, 4.88, and 21.00 mg of iodine per milliliter), then it was scanned with dual-energy CT with and without an outer fat ring to simulate large body size (total diameter, 42 cm). Two readers independently reviewed conventional 120-kVp CT and 40-keV monoenergetic dual-energy CT images to record the presence of polyps and confidence (three-point scale.) Generalized estimating equations were used for sensitivity comparisons between conventional CT and dual-energy CT, and a Wilcoxon signed-rank test was used for reader confidence. Results Dual-energy CT had higher overall sensitivity for polyp detection than conventional CT (58.8%; 95% confidence interval [CI]: 49.7%, 67.3%; 564 of 960 polyps vs 42.1%; 95% CI: 32.1%, 52.8%; 404 of 960 polyps; P < .001), including with the fat ring (48% and 31%, P < .001). Reader confidence improved with dual-energy CT compared with conventional images on all tagging levels (P < .001). Interrater agreement was substantial (κ = 0.74; 95% CI: 0.70, 0.77). Conclusion Compared with conventional 120-kVp CT, dual-energy CT improved polyp detection and reader confidence in a dedicated dual-energy CT colonography phantom, especially with suboptimal fecal tagging. © RSNA, 2020.

Bowel preparation in CT colonography: Is diet restriction necessary? A randomised trial (DIETSAN)

OBJECTIVES

To investigate whether diet restriction affects quality of colon cleansing and patient tolerance during reduced bowel preparation for CT colonography (CTC).

METHODS

Asymptomatic and symptomatic patients were enrolled in this pragmatic, single-centre, randomised trial. All patients were randomly assigned (1:1 ratio, blocks of ten) to receive a reduced bowel preparation and faecal tagging with (Diet-Restriction-Group [DR]) or without (No-Diet-Restriction-Group [NDR]) dietary restriction. Five readers performed a blinded subjective image analysis, by means of 4-point Likert-scales from 0 (highest score) to 3 (worst score). Endpoints were the quality of large bowel cleansing and tolerance to the assigned bowel preparation regimen. The trial is registered at ClinicalTrial.gov (URomLSDBAL1).

RESULTS

Ninety-five patients were randomly allocated to treatments (48 in NDR-group, 47 in DR-group). Both groups resulted in optimal colon cleansing. The mean residual stool (0.22, 95%CI 0.00-0.44) and fluid burden (0.39, 95%CI 0.25-0.53) scores for patients in DR-group were similar to those in patients in NDR-group (0.25, 95%CI 0.03-0.47 [p = 0.82] and 0.49, 95%CI 0.30-0.67 [p = 0.38], respectively). Tolerance was significantly better in NDR-group.

CONCLUSION

A reduced bowel preparation in association with faecal tagging and without any dietary restriction demonstrated optimal colon cleansing effectiveness for CTC, providing better patient compliance compared with dietary restriction.

KEY POINTS

• Dietary restriction in reduced bowel preparation regimen can be avoided. • The quality of colon cleansing is not affected by dietary restriction. • The quality of faecal tagging is not affected by dietary restriction. • Avoidance of dietary restriction improves patients' tolerance for CTC.

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.

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.

Value of Virtual Colonoscopy with 64 Row CT in Evaluation of Colorectal Cancer

Background

Virtual colonoscopy (VC) enables three-dimensional view of walls and internal lumen of the colon as a result of reconstruction of multislice CT images. The role of VC in diagnosis of the colon abnormalities systematically increases, and in many medical centers all over the world is carried out as a screening test of patients with high risk of colorectal cancer.

Material/Methods

We analyzed results of virtual colonoscopy of 360 patients with clinical suspicion of colorectal cancer. Sensitivity and specificity of CT colonoscopy for detection of colon cancers and polyps were assessed.

Results

Results of our research have shown high diagnostic efficiency of CT colonoscopy in detection of focal lesions in large intestine of 10 mm or more diameter. Sensitivity was 85.7%, specificity 89.2%.

Conclusions

Virtual colonoscopy is noninvasive and well tolerated by patients imaging method, which permits for early detection of the large intestine lesions with specificity and sensitivity similar to classical colonoscopy in screening exams in patients suspected for colorectal cancer. Good preparation of the patients for the examination is very important for proper diagnosis and interpretation of this imaginge procedure.

Information-Preserving Pseudo-Enhancement Correction for Non-Cathartic Low-Dose Dual-Energy CT Colonography

In CT colonography (CTC), orally administered positive-contrast fecal-tagging agents can cause artificial elevation of the observed radiodensity of adjacent soft tissue. Such pseudo-enhancement makes it challenging to differentiate polyps and folds reliably from tagged materials, and it is also present in dual-energy CTC (DE-CTC). We developed a method that corrects for pseudo-enhancement on DE-CTC images without distorting the dual-energy information contained in the data. A pilot study was performed to evaluate the effect of the method visually and quantitatively by use of clinical non-cathartic low-dose DE-CTC data from 10 patients including 13 polyps covered partially or completely by iodine-based fecal tagging. The results indicate that the proposed method can be used to reduce the pseudo-enhancement distortion of DE-CTC images without losing material-specific dual-energy information. The method has potential application in improving the accuracy of automated image-processing applications, such as computer-aided detection and virtual bowel cleansing in CTC.

Bowel cleansing before CT colonography: comparison between two minimal-preparation regimens

AIM

To compare two regimens of reduced bowel preparation and faecal tagging for CT colonography.

MATERIALS AND METHODS

Single centre, prospective, randomized, noninferiority study, in which 52 consecutive adults underwent routine CT colonography. Patients, following a three-day low-fibre diet, received one of the two reduced preparations: 1-L polyethylene glycol and four tablets of bisacodyl in association with 90 mL of Iopamidol for faecal tagging administered on the same day as CTC examination (group 1); or a standard "iodine-only" preparation, consisting in 180 ml of Iopamidol the day before the examination (group 2). Primary outcome was the overall quality of bowel preparation.

RESULTS

Twenty-six patients per group were included. Per segment analysis showed preparation of diagnostic quality in 97.4% of segments in group 1 and in 95.5% in group 2 (p = ns). Per-patient analysis showed optimal quality of preparation in 76.9% of patients in group 1 and in 84.6% in group 2 (p = ns). Patient tolerability to both preparations was not different.

CONCLUSION

A limited bowel preparation consisting of 1-L PEG and four tablets of bisacodyl in association with 90 mL of Iodine for faecal tagging administered on the same day as CTC examination is feasible and offers bowel cleansing comparable to "iodine-only" preparation.

KEY POINTS

• Low-dose PEG bisacodyl and Iopamidol preparation is feasible, providing adequate bowel cleansing. • Faecal tagging is not different from the two limited preparations. • Patient tolerability to the two colon cleansing regimens is similar.

Quantifying public preferences for different bowel preparation options prior to screening CT colonography: a discrete choice experiment

OBJECTIVES

CT colonography (CTC) may be an acceptable test for colorectal cancer screening but bowel preparation can be a barrier to uptake. This study tested the hypothesis that prospective screening invitees would prefer full-laxative preparation with higher sensitivity and specificity for polyps, despite greater burden, over less burdensome reduced-laxative or non-laxative alternatives with lower sensitivity and specificity.

DESIGN

Discrete choice experiment.

SETTING

Online, web-based survey.

PARTICIPANTS

2819 adults (45-54 years) from the UK responded to an online invitation to take part in a cancer screening study. Quota sampling ensured that the sample reflected key demographics of the target population and had no relevant bowel disease or medical qualifications. The analysis comprised 607 participants.

INTERVENTIONS

After receiving information about screening and CTC, participants completed 3-4 choice scenarios. Scenarios showed two hypothetical forms of CTC with different permutations of three attributes: preparation, sensitivity and specificity for polyps.

PRIMARY OUTCOME MEASURES

Participants considered the trade-offs in each scenario and stated their preferred test (or chose neither).

RESULTS

Preparation and sensitivity for polyps were both significant predictors of preferences (coefficients: -3.834 to -6.346 for preparation, 0.207-0.257 for sensitivity; p<0.0005). These attributes predicted preferences to a similar extent. Realistic specificity values were non-significant (-0.002 to 0.025; p=0.953). Contrary to our hypothesis, probabilities of selecting tests were similar for realistic forms of full-laxative, reduced-laxative and non-laxative preparations (0.362-0.421). However, they were substantially higher for hypothetical improved forms of reduced-laxative or non-laxative preparations with better sensitivity for polyps (0.584-0.837).

CONCLUSIONS

Uptake of CTC following non-laxative or reduced-laxative preparations is unlikely to be greater than following full-laxative preparation as perceived gains from reduced burden may be diminished by reduced sensitivity. However, both attributes are important so a more sensitive form of reduced-laxative or non-laxative preparation might improve uptake substantially.

Noncathartic CT colonography: Image quality assessment and performance and in a screening cohort

OBJECTIVE

Cathartic bowel preparation is a major barrier for colorectal cancer screening. We examined noncathartic CT colonography (CTC) quality and performance using four similar bowel-tagging regimens in an asymptomatic screening cohort.

SUBJECTS AND METHODS

This prospective study included 564 asymptomatic subjects who underwent noncathartic CTC without dietary modification but with 21 g of barium with or without iodinated oral contrast material (four regimens). The quality of tagging with oral agents was evaluated. A gastrointestinal radiologist evaluated examinations using primary 2D search supplemented by electronic cleansing (EC) and 3D problem solving. Results were compared with complete colonoscopy findings after bowel purgation and with retrospective unblinded evaluation in 556 of the 564 (99%) subjects.

RESULTS

Of the 556 subjects, 7% (37/556) and 3% (16/556) of patients had 52 and 20 adenomatous polyps ≥ 6 and ≥ 10 mm, respectively. The addition of iodine significantly improved the percentage of labeled stool (p ≤ 0.0002) and specificity (80% vs 89-93%, respectively; p = 0.046). The overall sensitivity of noncathartic CTC for adenomatous polyps ≥ 6 mm was 76% (28/37; 95% CI, 59-88%), which is similar to the sensitivity of the iodinated regimens with most patients (sensitivity: 231 patients, 74% [14/19; 95% CI, 49-91%]; 229 patients, 80% [12/15; 95% CI, 52-96%]). The negative predictive value was 98% (481/490), and the lone cancer was detected (0.2%, 1/556). EC was thought to improve conspicuity of 10 of 21 visible polyps ≥ 10 mm.

CONCLUSION

In this prospective study of asymptomatic subjects, the per-patient sensitivity of noncathartic CTC for detecting adenomas ≥ 6 mm was approximately 76%. Inclusion of oral iodine contrast material improves examination specificity and the percentage of labeled stool. EC may improve polyp conspicuity.

Barriers to screening colonoscopy in an urban population: a study to help focus further efforts to attain full compliance

BACKGROUND

Awareness of colorectal cancer and decision for colorectal cancer screening is influenced by multiple factors including ethnicity, level of education, and adherence to regular medical follow up.

OBJECTIVE

Our survey aimed at assessing barriers to colorectal cancer screening among urban population.

DESIGN

This study is a survey of the general population.

SETTING

This study was made at a local community in the downtown area of a metropolitan city.

PATIENTS/SUBJECTS

The study population for this survey included 2000 non-institutionalized residents from local community of Brooklyn downtown area of City of Brooklyn, NY, USA. All participants were 50 years or older.

INTERVENTION

No intervention was done.

MAIN OUTCOME MEASUREMENT

The survey questionnaire collected information about demographic, socioeconomic level, awareness of various cancers and their screening methods, and awareness of screening colonoscopy.

RESULTS

Colonoscopy was identified as the best screening test by 31 % of the subjects. Pain and discomfort was the major reason for not having a colonoscopy. The fear of a complication declined significantly after the first colonoscopy but fear of pain and discomfort increased. Difficulty with bowel preparation before a colonoscopy was a significant problem; it discouraged significant number of participants from having another colonoscopy.

LIMITATION

This study is limited by its small sample size.

CONCLUSION

Physician/family and peer influence seems important but influencing only a minority of subjects. Fear of complications should be allayed using accurate statistical information. Pain should be significantly diminished and/or eliminated during colonoscopy. Future research should focus to minimize complexity and discomfort associated with bowel preparation.

Predictors of CT colonography utilization among asymptomatic medicare beneficiaries

BACKGROUND

Although the Centers for Medicare and Medicaid Services (CMS) denied coverage for screening computed tomography colonography (CTC) in March 2009, little is understood about whether CTC was targeted to the appropriate patient population prior to this decision.

OBJECTIVE

Evaluate patient characteristics and known relative clinical indications for screening CTC among patients who received CTC compared to optical colonoscopy (OC).

DESIGN/PARTICIPANTS

Cross-sectional study of all 10,538 asymptomatic Medicare beneficiaries who underwent CTC between January 2007 and December 2008, compared to a cohort of 160,113 asymptomatic beneficiaries who underwent OC, matched on county of residence and year of examination.

MAIN MEASURES

Patient characteristics and known relative appropriate and inappropriate clinical indications for screening CTC.

KEY RESULTS

CTC utilization was higher among women, patients > 65 years of age, white patients, and those with household income > 75 % (p = 0.001). Patients with relatively appropriate clinical indications for screening CTC were more likely to undergo CTC than OC including presumed incomplete OC (OR 80.7, 95 % CI 76.01-85.63); sedation risk (OR 1.11, 95 % CI 1.05-1.17); and chronic anticoagulation risk (OR 1.46, 95 % CI 1.38-1.54), after adjusting for patient characteristics and known clinical indications. Conversely, patients undergoing high-risk screening, an inappropriate indication, were less likely to receive CTC (OR 0.4, 95 % CI 0.37-0.42). Overall, 83 % of asymptomatic patients referred to CTC had at least one clinical indication relatively appropriate for CTC (8,772/10,538).

CONCLUSION

During the 2 years preceding CMS denial for screening, CTC was targeted to asymptomatic patients with relatively appropriate clinical indications for CTC/not receiving OC. However, CTC utilization was lower among certain demographic groups, including minority patients. These findings raise the possibility that future coverage of screening CTC might exacerbate disparities in colorectal cancer screening while increasing overall screening rates.

Volumetric detection of colorectal lesions for noncathartic dual-energy computed tomographic colonography

Noncathartic computed tomographic colonography (CTC) could significantly increase patient adherence to colorectal screening guidelines. However, radiologists find the interpretation of noncathartic CTC images challenging. We developed a fully automated computer-aided detection (CAD) scheme for assisting radiologists with noncathartic CTC. A volumetric method is used to detect lesions within a thick target region encompassing the colonic wall. Dual-energy CTC (DE-CTC) is used to provide more detailed information about the colon than what is possible with conventional CTC. False-positive detections are reduced by use of a random-forest classifier. The effect of the thickness of the target region on detection performance was assessed by use of 22 clinical noncathartic DE-CTC studies including 27 lesions ≥6 mm. The results indicate that the thickness parameter can have significant effect on detection accuracy. Leave-one-patient-out evaluation indicated that the proposed CAD scheme detects colorectal lesions at high accuracy in noncathartic CTC.

Partial preparation computed tomographic colonography: a feasibility study

We retrospectively evaluated computed tomographic colonography examinations of patients who have had a partial bowel preparation and compared the quality of their preparation with patients who have had a full bowel preparation. In total, 27 patients undergoing computed tomographic colonography examination (10 patients with partial bowel preparation and 17 with full bowel preparation) had their examinations retrospectively reviewed by three independent radiologists in a blinded manner, with evaluation of residual stool, distention, residual fluid, and overall bowel preparation quality. Six colon segments were evaluated individually and independently for these four variables (a total of 161 segments tested). Comparisons were made with the Mann-Whitney test between the partial preparation group and the full preparation group. Partial preparation included stool and fluid tagging plus 20 mg of bisacodyl orally; full preparation included stool and fluid tagging plus 2 L of polyethylene glycol solution. No significant clinical difference was found in colon preparation between the partial and full bowel preparation groups--when evaluated with individual colon segments or by independent readers. Interreader correlation was high. This pilot study indicates that full bowel preparation is not required for diagnostic-quality computed tomographic colonography examination. Further evaluation of this partial bowel preparation regimen is warranted.

CT colonography without cathartic preparation: positive predictive value and patient experience in clinical practice

OBJECTIVE

To determine the positive predictive value (PPV) for polyps ≥ 6 mm detected at CT colonography (CTC) performed without cathartic preparation, with low-dose iodine faecal tagging regimen and to evaluate patient experience.

METHODS

1920 average-risk patients underwent CTC without cathartic preparation. Faecal tagging was performed by diatrizoate meglumine and diatrizoate sodium at a total dose of 60 ml (22.2 g of iodine).The standard interpretation method was primary 3D with 2D problem solving. We calculated per-patient and per-polyp PPV in relation to size and morphology. All colonic segments were evaluated for image quality (faecal tagging, amount of liquid and solid residual faeces and luminal distension). Patients completed a questionnaire before and after CTC to assess preparation and examination experience.

RESULTS

Per-polyp PPV for detected lesions of ≥ 6 mm, 6-9 mm, ≥ 10 mm and ≥ 30 mm were 94.3%, 93.1%, 94.7% and 98%, respectively. Per-polyp PPV, according to lesion morphology, was 94.6%, 97.3% and 85.1% for sessile, pedunculated and flat polyps, respectively. Per-patient PPV was 92.8%. Preparation without frank cathartics was reported to cause minimal discomfort by 78.9% of patients.

CONCLUSION

CTC without cathartic preparation and low-dose iodine faecal tagging may yield high PPVs for lesions ≥ 6 mm and is well accepted by patients.

KEY POINTS

• Computed tomographic colonography (CTC) without cathartic preparation is well accepted by patients • Cathartic-free faecal tagging CTC yields high positive predictive values • CTC without cathartic preparation could improve uptake of colorectal cancer screening.

Reduced cathartic bowel preparation for CT colonography: prospective comparison of 2-L polyethylene glycol and magnesium citrate

PURPOSE

To prospectively compare adequacy of colonic cleansing, adequacy of solid stool and fluid tagging, and patient acceptance by using reduced-volume, 2-L polyethylene glycol (PEG) versus magnesium citrate bowel preparations for CT colonography.

MATERIALS AND METHODS

This study was approved by the institutional Committee on Human Research and was compliant with HIPAA; all patients provided written consent. In this randomized, investigator-blinded study, 50 patients underwent oral preparation with either a 2-L PEG or a magnesium citrate solution, tagging with oral contrast agents, and subsequent CT colonography and segmentally unblinded colonoscopy. The residual stool (score 0 [best] to 3 [worst]) and fluid (score 0 [best] to 4 [worst]) burden and tagging adequacy were qualitatively assessed. Residual fluid attenuation was recorded as a quantitative measure of tagging adequacy. Patients completed a tolerance questionnaire within 2 weeks of scanning. Preparations were compared for residual stool and fluid by using generalized estimating equations; the Mann-Whitney test was used to compare the qualitative tagging score, mean residual fluid attenuation, and adverse effects assessed on the patient experience questionnaire.

RESULTS

The mean residual stool (0.90 of three) and fluid burden (1.05 of four) scores for PEG were similar to those for magnesium citrate (0.96 [P = .58] and 0.98 [P = .48], respectively). However, the mean fecal and fluid tagging scores were significantly better for PEG (0.48 and 0.28, respectively) than for magnesium citrate (1.52 [P < .01] and 1.28 [P < .01], respectively). Mean residual fluid attenuation was higher for PEG (765 HU) than for magnesium citrate (443 HU, P = .01), and mean interpretation time was shorter for PEG (14.8 minutes) than for magnesium citrate (18.0 minutes, P = .04). Tolerance ratings were not significantly different between preparations.

CONCLUSION

Reduced-volume PEG and magnesium citrate bowel preparations demonstrated adequate cleansing effectiveness for CT colonography, with better tagging and shorter interpretation time observed in the PEG group. Adequate polyp detection was maintained but requires further validation because of the small number of clinically important polyps.

Current techniques in the performance, interpretation, and reporting of CT colonography

The technical objective of computed tomographic colonography (CTC) is to acquire high-quality computed tomography images of the cleansed, well-distended colon for polyp detection. In this article the authors provide an overview of the technical components of CTC, from preparation of the patient to acquisition of the imaging data and basic methods of interpretation. In each section, the best evidence for current practices and recommendations is reviewed. Each of the technical components must be optimized to achieve high sensitivity in polyp detection.

Informatics in radiology: Electronic cleansing for noncathartic CT colonography: a structure-analysis scheme

Computed tomographic (CT) colonography performed after tagging of fecal matter but without a cathartic agent, or noncathartic CT colonography (also known as laxative-free CT colonography), is regarded as a promising next-generation technique for reducing or eliminating the discomfort associated with cathartic bowel preparation, which is the major barrier to undergoing colon cancer screening. Electronic cleansing is an emerging technique for the removal of tagged fecal materials from CT colonographic images. Three major electronic cleansing artifacts--soft-tissue degradation, pseudo-soft-tissue structures, and incomplete cleansing--severely impair the quality of electronically cleansed noncathartic CT colonographic images and limit the diagnostic utility of this modality. A structure-analysis electronic cleansing scheme was developed that makes use of local morphologic information to identify submerged colonic soft-tissue structures while removing the tagged material. Combined with other cutting-edge image processing techniques, including local roughness analysis, mosaic decomposition, and level set segmentation, structure-analysis cleansing helps eliminate the aforementioned artifacts, providing diagnostic-quality cleansed CT colonographic images for the detection of colon cancer. Noncathartic CT colonography with the application of structure-analysis cleansing is expected to help promote CT colonography as a patient-friendly method of colorectal cancer screening.

Comparison of three different iodine-based bowel regimens for CT colonography

OBJECTIVE

The aim of this study was to compare the computed tomographic colonography (CTC) image quality and patient acceptance of three iodine-based faecal tagging bowel preparations in 60 patients undergoing the following regimens: a 2-day regimen of meal-time administration of iodine and phospho-soda (GFPH); a 2-day regimen of meal-time mild laxative, followed by iodine administered 2 h before CTC (SD); and a 2-day regimen of meal-time administration of iodine (GF).

METHODS

Two independent radiologists assessed tagging quality; quantitative measures included the tagged stool density, and computer-aided detection (CAD) false-positive rate.

RESULTS

The GFPH and SD regimens provided better subjective quality than GF (p < 0.001). The latter regimen resulted in a higher proportion of insufficiently tagged segments: the measured average stool density was less than 200 HU in 10.7% in all segments vs 3.6% for SD and <0.5% for GFPH, respectively. Insufficient tagging occurred mostly in the ascending colon and the caecum. The CAD false-positive rate increased following the trend: GFPH < SD < GF (p = 0.00012). GFPH was worse tolerated than SD (p < 0.05).

CONCLUSIONS

Considering preparation quality alone, GFPH was the best regimen, but SD provided the best balance between bowel preparation quality and patient acceptability.

CT colonography with limited bowel preparation: prospective assessment of patient experience and preference in comparison to optical colonoscopy with cathartic bowel preparation

The purpose of this study was to prospectively compare participant experience and preference of limited preparation computed tomography colonography (CTC) with full-preparation colonoscopy in a consecutive series of patients at increased risk of colorectal cancer. CTC preparation comprised 180 ml diatrizoate meglumine, 80 ml barium and 30 mg bisacodyl. For the colonoscopy preparation 4 l of polyethylene glycol solution was used. Participants’ experience and preference were compared using the Wilcoxon signed rank test and the chi-squared test, respectively. Associations between preference and experience parameters for the 173 participants were determined by logistic regression. Diarrhoea occurred in 94% of participants during CTC preparation. This side effect was perceived as severely or extremely burdensome by 29%. Nonetheless, the total burden was significantly lower for the CTC preparation than for colonoscopy (9% rated the CTC preparation as severely or extremely burdensome compared with 59% for colonoscopy; p < 0.001). Participants experienced significantly more pain, discomfort and total burden with the colonoscopy procedure than with CTC (p < 0.001). After 5 weeks, 69% preferred CTC, 8% were indifferent and 23% preferred colonoscopy (p < 0.001). A burdensome colonoscopy preparation and pain at colonoscopy were associated with CTC preference (p < 0.04). In conclusion, participants’ experience and preference were rated in favour of CTC with limited bowel preparation compared with full-preparation colonoscopy.

Association between rectal optical signatures and colonic neoplasia: potential applications for screening

Field carcinogenesis detection represents a promising means for colorectal cancer (CRC) screening, although current techniques (e.g., flexible sigmoidoscopy) lack the requisite sensitivity. The novel optical technology low-coherence enhanced backscattering (LEBS) spectroscopy, allows identification of microscale architectural consequences of the field carcinogenesis in preclinical CRC models with unprecedented accuracy. To investigate the potential clinical translatability of this approach, we obtained biopsies from the normal-appearing rectal mucosa from patients undergoing colonoscopy (n = 219). LEBS signals were recorded through a bench-top instrument. Four parameters characterizing LEBS signal were linearly combined into a single marker. We found that LEBS signal parameters generally mirrored neoplasia progression from patients with no neoplasia, to 5 to 9 mm adenoma and to advanced adenomas. The composite LEBS marker calculated from the LEBS signal paralleled this risk status (ANOVA P < 0.001). Moreover, this was independent of CRC risk factors, benign colonic findings, or clinically unimportant lesions (diminutive adenomas, hyperplastic polyps). For advanced adenomas, the LEBS marker had a sensitivity of 100%, specificity of 80%, and area under the receiver operator characteristic curve of 0.895. Leave-one-out cross-validation and an independent data set (n = 51) supported the robustness of these findings. In conclusion, we provide the first demonstration that LEBS-detectable alterations in the endoscopically normal rectum were associated with the presence of neoplasia located elsewhere in the colon. This study provides the proof of concept that rectal LEBS analysis may potentially provide a minimally intrusive CRC screening technique. Further studies with an endoscopically compatible fiber optic probe are under way for multicenter clinical validation.

CT colonography versus optical colonoscopy for screening asymptomatic patients for colorectal cancer a patient, intervention, comparison, outcome (PICO) analysis

RATIONALE AND OBJECTIVES

The American College of Radiology has recently endorsed the use of computed tomographic colonography (CTC) for colon cancer screening. With advances in technology and postprocessing software, the quality of computed tomographic colonographic studies has improved, and new techniques are being developed to reduce radiation exposure and increase patient acceptance of the procedure. The aim of colorectal cancer screening is to reduce the incidence of malignancy by identifying and removing presymptomatic lesions. The aim of this study was to answer the clinical question: In an asymptomatic patient at average risk for colon cancer, is CTC equivalent to optical colonoscopy (OC) for detecting clinically significant polyps?

MATERIALS AND METHODS

A systematic literature review was conducted to evaluate CTC compared to OC, using the patient, intervention, comparison intervention, outcome (PICO) search strategy. The PubMed search used Medical Subject Headings, including the terms "computed tomography colonography," "colonoscopy," "screening," and "polyp." Each of the retrieved articles was assigned a level of evidence using the Centre for Evidence-Based Medicine's hierarchy of validity for diagnostic studies.

RESULTS

PICO search criteria and review of abstracts identified 16 relevant studies. Using the Centre for Evidence-Based Medicine's hierarchy of validity, there were three level 1c studies, two level 2a studies, three level 2b studies, four level 3b studies, two level 4 studies, and two level 5 studies. All relevant studies demonstrated that CTC had high or moderately high per patient and per polyp sensitivity and specificity compared to OC for clinically relevant polyps (>5 mm).

CONCLUSIONS

The majority of evidence suggests that CTC is an acceptable alternative to OC, particularly in the group of patients who are either unwilling or unable to undergo OC. The results of the large, multicenter American College of Radiology Imaging Network study are pending. This trial presented preliminary results in 2007 suggesting that the sensitivity and specificity of CTC are high and comparable to those of OC.

Virtual tagging for laxative-free CT colonography: pilot evaluation

Laxative-free computed tomographic colonography (lfCTC) could significantly improve patient adherence to colorectal screening. However, the interpretation of lfCTC data is complicated by the presence of poorly tagged feces and partial-volume artifacts that imitate colorectal lesions. The authors developed a method for virtual tagging of such artifacts. A probabilistic model of colonic wall was developed, and virtual tagging was performed on artifacts that were identified by the model. The method was evaluated with 46 clinical lfCTC cases that were prepared with dietary fecal tagging only. Visual examples show that the method can label partial-volume artifacts, poorly tagged feces, nonadhering completely untagged feces, and artifacts such as rectal tubes. The effect of virtual tagging was evaluated by comparing the detection accuracy of a fully automated polyp detection scheme without and with the method. With virtual tagging, the per-lesion detection sensitivity was 100% for lesions > or = 10 mm (n = 4) with 3.8 false positives per patient (per two CT scan volumes) and 90% for lesions > or = 6 mm (n = 10) with 5.4 false positives per patient on average. The improvement in detection performance by virtual tagging was statistically significant (p = 0.03; JAFROC and JAFROC-1).

Efficacy of barium-based fecal tagging for CT colonography: a comparison between the use of high and low density barium suspensions in a Korean population - a preliminary study

OBJECTIVE

This preliminarily study was designed to determine and to compare the efficacy of two commercially available barium-based fecal tagging agents for CT colonography (CTC) (high-density [40% w/v] and low-density [4.6% w/v] barium suspensions) in a population in Korea.

MATERIALS AND METHODS

In a population with an identified with an average-risk for colorectal cancer, 15 adults were administered three doses of 20 ml 40% w/v barium for fecal tagging (group I) and 15 adults were administered three doses of 200 ml 4.6% w/v barium (group II) for fecal tagging. Excluding five patients in group I and one patient in group II that left the study, ten patients in group I and 14 patients in group II were finally included in the analysis. Two experienced readers evaluated the CTC images in consensus regarding the degree of tagging of stool pieces 6 mm or larger. Stool pieces were confirmed with the use of standardized CTC criteria or the absence of matched lesions as seen on colonoscopy. The rates of complete fecal tagging were analyzed on a per-lesion and a per-segment basis and were compared between the patients in the two groups.

RESULTS

Per-lesion rates of complete fecal tagging were 52% (22 of 42; 95% CI, 37.7-66.6%) in group I and 78% (28 of 36; 95% CI, 61.7-88.5%) in group II. The difference between the two groups did not reach statistical significance (p = 0.285). The per-segment rates of complete tagging were 33% (6 of 18; 95% CI, 16.1%-56.4%) in group I and 60% (9 of 15; 95% CI, 35.7%-80.3%) in group II; again, the difference between the two groups did not reach statistical significance (p = 0.171).

CONCLUSION

Barium-based fecal tagging using both the 40% w/v and the 4.6% w/v barium suspensions showed moderate tagging efficacy. The preliminary comparison did not demonstrate a statistically significant difference in the tagging efficacy between the use of the two tagging agents, despite the tendency toward better tagging with the use of the 4.6% w/v barium suspension.

Adaptive correction of the pseudo-enhancement of CT attenuation for fecal-tagging CT colonography

In fecal-tagging CT colonography (ftCTC), positive-contrast tagging agents are used for opacifying residual bowel materials to facilitate reliable detection of colorectal lesions. However, tagging agents that have high radiodensity tend to artificially elevate the observed CT attenuation of nearby materials toward that of tagged materials on Hounsfield unit (HU) scale. We developed an image-based adaptive density-correction (ADC) method for minimizing such pseudo-enhancement effect in ftCTC data. After the correction, we can confidently assume that soft-tissue materials and air are represented by their standard CT attenuations, whereas higher CT attenuations indicate tagged materials. The ADC method was optimized by use of an anthropomorphic phantom filled partially with three concentrations of a tagging agent. The effect of ADC on ftCTC was assessed visually and quantitatively by comparison of the accuracy of computer-aided detection (CAD) without and with the use of the ADC method in two different types of clinical ftCTC databases: 20 laxative ftCTC cases with 24 polyps, and 23 reduced-preparation ftCTC cases with 28 polyps. Visual evaluation indicated that ADC minimizes the observed pseudo-enhancement effect. With ADC, the free-response receiver operating characteristic curves indicating CAD performance in polyp detection yielded normalized partial area-under-curve values of 0.91 and 0.80 for the two databases, respectively, with statistically significant improvement over conventional thresholding-based approaches (p<0.05). The results indicate that ADC is a useful method for reducing the pseudo-enhancement effect and for improving CAD performance in CTC.