Full-laxative versus minimum-laxative fecal-tagging CT colonography using 64-detector row CT: prospective blinded comparison of diagnostic performance, tagging quality, and patient acceptance

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.

A generative flow-based model for volumetric data augmentation in 3D deep learning for computed tomographic colonography

Purpose

Deep learning can be used for improving the performance of computer-aided detection (CADe) in various medical imaging tasks. However, in computed tomographic (CT) colonography, the performance is limited by the relatively small size and the variety of the available training datasets. Our purpose in this study was to develop and evaluate a flow-based generative model for performing 3D data augmentation of colorectal polyps for effective training of deep learning in CADe for CT colonography.

Methods

We developed a 3D-convolutional neural network (3D CNN) based on a flow-based generative model (3D Glow) for generating synthetic volumes of interest (VOIs) that has characteristics similar to those of the VOIs of its training dataset. The 3D Glow was trained to generate synthetic VOIs of polyps by use of our clinical CT colonography case collection. The evaluation was performed by use of a human observer study with three observers and by use of a CADe-based polyp classification study with a 3D DenseNet.

Results

The area-under-the-curve values of the receiver operating characteristic analysis of the three observers were not statistically significantly different in distinguishing between real polyps and synthetic polyps. When trained with data augmentation by 3D Glow, the 3D DenseNet yielded a statistically significantly higher polyp classification performance than when it was trained with alternative augmentation methods.

Conclusion

The 3D Glow-generated synthetic polyps are visually indistinguishable from real colorectal polyps. Their application to data augmentation can substantially improve the performance of 3D CNNs in CADe for CT colonography. Thus, 3D Glow is a promising method for improving the performance of deep learning in CADe for CT colonography.

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

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

Comparison of two Meglumine-Diatrizoate based bowel preparations for computed tomography colonography: Comparison of patient symptoms and bowel preparation quality

INTRODUCTION

To investigate the impact of two Meglumine-Diatrizoate based bowel preparation regimes for computed tomography colonography (CTC) on the patient experience and image quality.

METHODS

100 patients consumed Meglumine-Diatrizoate at 24 h and 12 h prior to the CTC examination. 50 patients followed regime 1 (50:50), 50 ml of Meglumine-Diatrizoate at both 24 and 12 h prior to the examination. 50 patients followed regime 2 (75:25), 75 ml of Meglumine-Diatrizoate at 24 h prior to the examination and 25 ml of Meglumine-Diatrizoate at 12 h prior to the examination. All patients completed a questionnaire to indicate the time of onset of adverse effects and when they were most severe. Five advanced practitioners assessed the image quality in a visual grading study. Visual grading characteristic (VGC) analysis was applied with regime 1 as the reference condition and regime 2 and test condition; test alpha was set at 0.05.

RESULTS

Image quality was assessed with successful bowel cleansing as the scoring criteria for the visual grading study. The bowel cleansing as provided by the two Meglumine-Diatrizoate regimes was revealed not to be statistically different, with the area under the VGC curve and 95% confidence intervals 0.487 (0.287, 0.701), p = 0.887. Patients taking the 75:25 bowel preparation experienced a shorter median time to the onset of adverse effects.

CONCLUSION

There was no observed difference in Image quality criteria score for the two Meglumine-Diatrizoate based bowel preparation with more predictable adverse effects of Meglumine-Diatrizoate with the 75:25 preparation.

IMPLICATIONS FOR PRACTICE

Providing patients with a higher contrast burden 24 h prior to CTC may have a positive impact on the patient experience without compromising image quality.

A novel volume-reduced CT colonography regimen using hypertonic laxative (polyethylene glycol with ascorbic acid): randomized controlled trial

OBJECTIVES

The aim of this study is to investigate the feasibility of bowel preparation using a hypertonic laxative (polyethylene glycol with ascorbic acid, PEG + Asc) for CT colonography (CTC) and to examine the volume limit of laxative.

METHODS

In one institution, patients who met the indications for CTC were enrolled and randomly assigned to CTC with regimen A (800 ml PEG + Asc), B (600 ml PEG + Asc), or C (400 ml PEG + Asc). Sodium diatrizoate was given orally for fecal tagging. On the previous day, patients ate low-residue meals and took the assigned lavage solution after dinner. A reader blinded to the preparation graded residual stool/fluid and fecal tagging quality in six segments of the colorectum. The primary outcome was a proportion of colon segments without stool. One hundred twenty segments in 20 patients with each regimen were needed to show a non-inferiority margin of 15%, assuming 85% of no stool.

RESULTS

A total of 360 segments in 60 patients were analyzed. There were 83% of segments with no stool in regimen A, 89% in regimen B, and 88% in regimen C. Using the delta method, the 95% confidence interval of the risk difference (6.7%) between regimens A and B was - 2.2% to 15.6%, and the risk difference (5.0%) between regimens A and C was - 4.1% to 14%, both within the non-inferiority margin. Residual fluid and fecal tagging quality were also within the non-inferiority margin. No adverse events occurred.

CONCLUSIONS

A novel CTC regimen using hypertonic laxative demonstrated optimal colon cleansing effectiveness even with the lowest volume of laxative (UMIN000022851).

KEY POINTS

• A novel CTC regimen using a hypertonic laxative is feasible. • The lowest volume of laxative provides excellent colon imaging. • However, the lowest volume of laxative did not improve patient acceptance.

Dual-energy computed tomography colonography using dual-layer spectral detector computed tomography: Utility of virtual monochromatic imaging for electronic cleansing

OBJECTIVE

To assess the utility of virtual monochromatic imaging (VMI) using a dual-layer spectral detector CT for electronic cleansing in fecal-tagging CT colonography (CTC).

METHODS

This study included 35 patients who underwent fecal-tagging CTC with a dual-layer detector spectral CT scanner. Conventional images at 120 kVp and VMI at 40, 50, and 60 keV were reconstructed. Quantitative image quality parameters, i.e., tagging density and image noise, were compared and the visual image quality was scored on a four-point scale. We recorded the number of the colon segments with appropriate tagging density (≥300 HU) for each patient and used these data to compare the reconstructions. In addition, electronic cleansing performance was semi-quantitatively assessed using a four-point scale.

RESULTS

The mean tagging density on VMI was significantly higher than that on conventional 120 kVp images. The number of colon segments with appropriate tagging density on VMI were significantly higher than that on conventional 120 kVp images. There was no significant difference among the reconstructed images with respect to image noise. Scores for subjective image quality and electronic cleansing performance on VMI were significantly higher than those on conventional 120 kVp images.

CONCLUSION

With dual-layer spectral detector CT, VMI can yield significantly better fecal-tagged CTC image quality and improve electronic cleansing performance.

Adverse events during CT colonography for screening, diagnosis and preoperative staging of colorectal cancer: a Japanese national survey

OBJECTIVES

To retrospectively evaluate the frequencies and magnitudes of adverse events associated with computed tomographic colonography (CTC) for screening, diagnosis and preoperative staging of colorectal cancer.

METHODS

A Japanese national survey on CTC was administered by use of an online survey tool in the form of a questionnaire. The questions covered mortality, colorectal perforation, vasovagal reaction, total number of examinations, and examination procedures. The survey data was collated and raw frequencies were determined. Fisher's exact test was used to determine differences in event rates between groups.

RESULTS

At 431 institutions, 147,439 CTC examinations were performed. No deaths were reported. Colorectal perforations occurred in 0.014% (21/147,439): 0.003% (1/29,823) in screening, 0.014% (13/91,007) in diagnosis and 0.028% (7/25,330) in preoperative staging. The perforation risk was significantly lower in screening than in preoperative staging CTC procedures (p = 0.028). Eighty-one per cent of perforation cases (17/21) did not require emergency surgery. Vasovagal reaction occurred in 0.081% (120/147,439): 0.111% (33/29,823) in screening, 0.088% (80/91,007) in diagnosis and 0.028% (7/25,330) in preoperative staging.

CONCLUSIONS

The risk of colorectal perforation and vasovagal reaction in CTC is low. The frequency of colorectal perforation associated with CTC is least in the screening group and greatest in the preoperative-staging group.

KEY POINTS

• The colorectal perforation rate during preoperative-staging CTC was 0.028 %. • The perforation rates for screening and diagnosis were 0.003 % and 0.014 %, respectively. • The perforation risk is significantly lower in screening than in preoperative staging. • Eighty-one per cent of perforation cases did not require emergency surgery. • Use of an automatic colon insufflator can reduce the risk of bowel perforation.

Accuracy of CT Colonography for Detection of Polypoid and Nonpolypoid Neoplasia by Gastroenterologists and Radiologists: A Nationwide Multicenter Study in Japan

OBJECTIVES

The objective of this study was to assess prospectively the diagnostic accuracy of computer-assisted computed tomographic colonography (CTC) in the detection of polypoid (pedunculated or sessile) and nonpolypoid neoplasms and compare the accuracy between gastroenterologists and radiologists.

METHODS

This nationwide multicenter prospective controlled trial recruited 1,257 participants with average or high risk of colorectal cancer at 14 Japanese institutions. Participants had CTC and colonoscopy on the same day. CTC images were interpreted independently by trained gastroenterologists and radiologists. The main outcome was the accuracy of CTC in the detection of neoplasms ≥6 mm in diameter, with colonoscopy results as the reference standard. Detection sensitivities of polypoid vs. nonpolypoid lesions were also evaluated.

RESULTS

Of the 1,257 participants, 1,177 were included in the final analysis: 42 (3.6%) were at average risk of colorectal cancer, 456 (38.7%) were at elevated risk, and 679 (57.7%) had recent positive immunochemical fecal occult blood tests. The overall per-participant sensitivity, specificity, and positive and negative predictive values for neoplasms ≥6 mm in diameter were 0.90, 0.93, 0.83, and 0.96, respectively, among gastroenterologists and 0.86, 0.90, 0.76, and 0.95 among radiologists (P<0.05 for gastroenterologists vs. radiologists). The sensitivity and specificity for neoplasms ≥10 mm in diameter were 0.93 and 0.99 among gastroenterologists and 0.91 and 0.98 among radiologists (not significant for gastroenterologists vs. radiologists). The CTC interpretation time by radiologists was shorter than that by gastroenterologists (9.97 vs. 15.8 min, P<0.05). Sensitivities for pedunculated and sessile lesions exceeded those for flat elevated lesions ≥10 mm in diameter in both groups (gastroenterologists 0.95, 0.92, and 0.68; radiologists: 0.94, 0.87, and 0.61; P<0.05 for polypoid vs. nonpolypoid), although not significant (P>0.05) for gastroenterologists vs. radiologists.

CONCLUSIONS

CTC interpretation by gastroenterologists and radiologists was accurate for detection of polypoid neoplasms, but less so for nonpolypoid neoplasms. Gastroenterologists had a higher accuracy in the detection of neoplasms ≥6 mm than did radiologists, although their interpretation time was longer than that of radiologists.

Diagnostic Performance and Patient Acceptance of Reduced-Laxative CT Colonography for the Detection of Polypoid and Non-Polypoid Neoplasms: A Multicenter Prospective Trial

Purpose To evaluate the diagnostic accuracy and patient acceptance of reduced-laxative computed tomographic (CT) colonography without computer-aided detection (CAD) for the detection of colorectal polypoid and non-polypoid neoplasms in a population with a positive recent fecal immunochemical test (FIT). Materials and Methods Institutional review board approval and written informed consent were obtained. This multicenter prospective trial enrolled patients who had positive FIT results. Reduced-laxative CT colonography and colonoscopy were performed on the same day. Patients received 380 mL polyethylene glycol solution, 20 mL iodinated oral contrast agent, and two doses of 20 mg mosapride the day before CT colonography. The main outcome measures were the accuracy of CT colonography for the detection of neoplasms 6 mm or larger in per-patient and per-lesion analyses and a survey of patient perceptions regarding the preparation and examination. The Clopper-Pearson method was used for assessing the 95% confidence intervals of per-patient and per-lesion accuracy. Survey scores were analyzed by using the Wilcoxon and χ² tests. Results Three hundred four patients underwent both CT colonography and colonoscopy. Per-patient sensitivity, specificity, positive predictive value, and negative predictive value of CT colonography for detecting neoplasms 10 mm or larger were 0.91 (40 of 44), 0.99 (255 of 258), 0.93 (40 of 43), and 0.98 (255 of 259), respectively; these values for neoplasms 6 mm or larger were 0.90 (71 of 79), 0.93 (207 of 223), 0.82 (71 of 87), and 0.96 (207 of 215), respectively. Per-lesion sensitivities for detection of polypoid and non-polypoid neoplasms 10 mm or larger were 0.95 (40 of 42) and 0.67 (six of nine), respectively; those for neoplasms 6 mm or larger were 0.90 (104 of 115) and 0.38 (eight of 21), respectively (P < .05 for both). Patient acceptance of preparation and examination with CT colonography was significantly higher than that with colonoscopy, and 62% (176 of 282) of patients would choose CT colonography as the first examination if they have a positive FIT result in the future. Conclusion Reduced-laxative CT colonography without CAD is accurate in the detection of polypoid neoplasms 6 mm or larger but is less accurate in the detection of non-polypoid neoplasms. Reduced-laxative CT colonography has high patient acceptance and is an efficient triage examination for patients with a positive FIT. ^© RSNA, 2016 Online supplemental material is available for this article.

Effect of listening to music and essential oil inhalation on patients undergoing screening CT colonography: a randomized controlled trial

OBJECTIVE

To prospectively evaluate the effect of listening to music and inhaling aroma oil on patients undergoing screening computed tomography colonography.

MATERIALS AND METHODS

Two hundred and twenty four participants were randomly allocated to one of the four groups including: (1) combined music and aroma, (2) music alone, (3) aroma alone, and (4)control. The visual analog scale for pain and a questionnaire were used for subjective outcomes. We also used a pre-test–post-test design to compare the differences in blood pressure and heart rate as objective outcomes.

RESULTS

There were no statistical differences between the control group and other groups in the visual analog scale or changes in heart rate. Changes in blood pressure were similar. Participants reported good overall experiences. There were no differences in terms of overall satisfaction, pain rating, willingness to repeat the computed tomography colonography procedure in the future, or preference between colonoscopy and computed tomography colonography. More participants using music and/or aroma requested music and/or aroma during the next computed tomography colonography (P < 0.0001).

CONCLUSION

Although audio and olfactory intervention had little effect on perceived pain or discomfort and vital signs, participants who listened to music and inhaled aroma during the computed tomography colonography preferred music and aroma during the next computed tomography colonography.

Colonic distention at CT colonography: randomized evaluation of both IV hyoscine butylbromide and automated carbon dioxide insufflation

OBJECTIVE

The purpose of this article is to evaluate the efficacy of IV hyoscine butylbromide as a bowel relaxant and automated carbon dioxide insufflation in CT colonography in terms of colonic distention and perceived burden. SUBJECTS AND METHODS; Two hundred twenty-four participants were randomly allocated to one of four groups: control (no bowel relaxant and IV saline placebo before CT colonography with manual carbon dioxide insufflation), hyoscine butylbromide (IV hyoscine butylbromide before examination with manual carbon dioxide insufflation), automated (no bowel relaxant before examination with automated carbon dioxide insufflation), and combined (hyoscine butylbromide before examination with automated carbon dioxide insufflation). The degree of colonic distention on a 4-point scale, examination time, and participants' satisfaction, as measured by their responses to a questionnaire, were assessed.

RESULTS

The mean distention grades of all the colonic segments and both positions were 3.22 in the control group, 3.28 in the hyoscine butylbromide group, 3.77 in the automated group, and 3.74 in the combined group. Compared with manual carbon dioxide insufflation, automated carbon dioxide insufflation significantly improved the clinical adequacy of colonic distention and shortened examination time. No statistically significant difference was seen in the clinical adequacy of distention between participants who received hyoscine butylbromide and those who did not, or in examination time. Overall, the participants' experiences were not different.

CONCLUSION

Colonic distention was statistically significantly improved by automated carbon dioxide insufflation, but not by the administration of hyoscine butylbromide. The participants' tolerance was similar in each group.

Evaluation of dose reduction and image quality in CT colonography: comparison of low-dose CT with iterative reconstruction and routine-dose CT with filtered back projection

OBJECTIVE

To prospectively evaluate the radiation dose and image quality comparing low-dose CT colonography (CTC) reconstructed using different levels of iterative reconstruction techniques with routine-dose CTC reconstructed with filtered back projection.

METHODS

Following institutional ethics clearance and informed consent procedures, 210 patients underwent screening CTC using automatic tube current modulation for dual positions. Examinations were performed in the supine position with a routine-dose protocol and in the prone position, randomly applying four different low-dose protocols. Supine images were reconstructed with filtered back projection and prone images with iterative reconstruction. Two blinded observers assessed the image quality of endoluminal images. Image noise was quantitatively assessed by region-of-interest measurements.

RESULTS

The mean effective dose in the supine series was 1.88 mSv using routine-dose CTC, compared to 0.92, 0.69, 0.57, and 0.46 mSv at four different low doses in the prone series (p < 0.01). Overall image quality and noise of low-dose CTC with iterative reconstruction were significantly improved compared to routine-dose CTC using filtered back projection. The lowest dose group had image quality comparable to routine-dose images.

CONCLUSIONS

Low-dose CTC with iterative reconstruction reduces the radiation dose by 48.5 to 75.1% without image quality degradation compared to routine-dose CTC with filtered back projection.

KEY POINTS

• Low-dose CTC reduces radiation dose ≥ 48.5% compared to routine-dose CTC. • Iterative reconstruction improves overall CTC image quality compared with FBP. • Iterative reconstruction reduces overall CTC image noise compared with FBP. • Automated exposure control with iterative reconstruction is useful for low-dose CTC.

Electronic cleansing for 24-h limited bowel preparation CT colonography using principal curvature flow

CT colonography (CTC) is one of the recommended methods for colorectal cancer screening. The subject's preparation is one of the most burdensome aspects of CTC with a cathartic bowel preparation. Tagging of the bowel content with an oral contrast medium facilitates CTC with limited bowel preparation. Unfortunately, such preparations adversely affect the 3-D image quality. Thus far, data acquired after very limited bowel preparation were evaluated with a 2-D reading strategy only. Existing cleansing algorithms do not work sufficiently well to allow a primary 3-D reading strategy. We developed an electronic cleansing algorithm, aimed to realize optimal 3-D image quality for low-dose CTC with 24-h limited bowel preparation. The method employs a principal curvature flow algorithm to remove heterogeneities within poorly tagged fecal residue. In addition, a pattern recognition-based approach is used to prevent polyp-like protrusions on the colon surface from being removed by the method. Two experts independently evaluated 40 CTC cases by means of a primary 2-D approach without involvement of electronic cleansing as well as by a primary 3-D method after electronic cleansing. The data contained four variations of 24-h limited bowel preparation and was based on a low radiation dose scanning protocol. The sensitivity for lesions ≥ 6 mm was significantly higher for the primary 3-D reading strategy (84%) than for the primary 2-D reading strategy (68%) (p = 0.031). The reading time was increased from 5:39 min (2-D) to 7:09 min (3-D) (p = 0.005); the readers' confidence was reduced from 2.3 (2-D) to 2.1 (3-D) ( p = 0.013) on a three-point Likert scale. Polyp conspicuity for cleansed submerged lesions was similar to not submerged lesions (p = 0.06). To our knowledge, this study is the first to describe and clinically validate an electronic cleansing algorithm that facilitates low-dose CTC with 24-h limited bowel preparation.

Computed tomographic colonography versus colonoscopy for investigation of patients with symptoms suggestive of colorectal cancer (SIGGAR): a multicentre randomised trial

BACKGROUND

Colonoscopy is the gold-standard test for investigation of symptoms suggestive of colorectal cancer; computed tomographic colonography (CTC) is an alternative, less invasive test. However, additional investigation after CTC is needed to confirm suspected colonic lesions, and this is an important factor in establishing the feasibility of CTC as an alternative to colonoscopy. We aimed to compare rates of additional colonic investigation after CTC or colonoscopy for detection of colorectal cancer or large (≥10 mm) polyps in symptomatic patients in clinical practice.

METHODS

This pragmatic multicentre randomised trial recruited patients with symptoms suggestive of colorectal cancer from 21 UK hospitals. Eligible patients were aged 55 years or older and regarded by their referring clinician as suitable for colonoscopy. Patients were randomly assigned (2:1) to colonoscopy or CTC by computer-generated random numbers, in blocks of six, stratified by trial centre and sex. We analysed the primary outcome-the rate of additional colonic investigation-by intention to treat. The trial is an International Standard Randomised Controlled Trial, number 95152621.

FINDINGS

1610 patients were randomly assigned to receive either colonoscopy (n=1072) or CTC (n=538). 30 patients withdrew consent, leaving for analysis 1047 assigned to colonoscopy and 533 assigned to CTC. 160 (30.0%) patients in the CTC group had additional colonic investigation compared with 86 (8.2%) in the colonoscopy group (relative risk 3.65, 95% CI 2.87-4.65; p<0.0001). Almost half the referrals after CTC were for small (<10 mm) polyps or clinical uncertainty, with low predictive value for large polyps or cancer. Detection rates of colorectal cancer or large polyps in the trial cohort were 11% for both procedures. CTC missed 1 of 29 colorectal cancers and colonoscopy missed none (of 55). Serious adverse events were rare.

INTERPRETATION

Guidelines are needed to reduce the referral rate after CTC. For most patients, however, CTC provides a similarly sensitive, less invasive alternative to colonoscopy.

FUNDING

NIHR Health Technology Assessment Programme, NIHR Biomedical Research Centres funding scheme, Cancer Research UK, EPSRC Multidisciplinary Assessment of Technology Centre for Healthcare, and NIHR Collaborations for Leadership in Applied Health Research and Care.

Pilot study on efficacy of reduced cathartic bowel preparation with polyethylene glycol and bisacodyl

AIM: To evaluate the efficacy of reduced cathartic bowel preparation with 2 L polyethylene glycol (PEG)-4000 electrolyte solution and 10 mg bisacodyl enteric-coated tablets for computed tomographic colonography (CTC).

METHODS: Sixty subjects who gave informed consent were randomly assigned to study group A, study group B or the control group. On the day prior to CTC, subjects in study group A were given 20 mL 40% wt/vol barium sulfate suspension before 3 mealtimes, 60 mL 60% diatrizoate meglumine diluted in 250 mL water after supper, and 10 mg bisacodyl enteric-coated tablets 1 h before oral administration of 2 L PEG-4000 electrolyte solution. Subjects in study group B were treated identically to those in study group A, with the exception of bisacodyl which was given 1 h after oral PEG-4000. Subjects in the control group were managed using the same strategy as the subjects in study group A, but without administration of bisacodyl. Residual stool and fluid scores, the attenuation value of residual fluid, and discomfort during bowel preparation in the three groups were analyzed statistically.

RESULTS: The mean scores for residual stool and fluid in study group A were lower than those in study group B, but the differences were not statistically significant. Subjects in study group A showed greater stool and fluid cleansing ability than the subjects in study group B. The mean scores for residual stool and fluid in study groups A and B were lower than those in the control group, and were significantly different. There was no significant difference in the mean attenuation value of residual fluid between study group A, study group B and the control group. The total discomfort index during bowel preparation was 46, 45 and 45 in the three groups, respectively, with no significant difference.

CONCLUSION: Administration of 10 mg bisacodyl enteric-coated tablets prior to or after oral administration of 2 L PEG-4000 electrolyte solution enhances stool and fluid cleansing ability, and has no impact on the attenuation value of residual fluid or the discomfort index. The former is an excellent alternative for CTC colorectum cleansing

Preference for colonoscopy versus computerized tomographic colonography: a systematic review and meta-analysis of observational studies

In recent years, colorectal cancer (CRC) screening using computerized tomographic colonography (CTC) has attracted considerable attention. In order to better understand patient preferences for CTC versus colonoscopy, we performed a systematic review and meta-analysis of the available literature. Data sources included published studies, abstracts and book chapters, in any language, with publication dates from 1995 through February 2012, and with prospective or retrospective enrollment of diagnostic or screening patients who had undergone both procedures and explicit assessment of their preference for colonoscopy versus CTC. A predefined algorithm identified eligible studies using computer and hand searches performed by two independent investigators. We used a mixed effects model to pool preference differences (defined as the proportion of subjects who preferred CTC minus the proportion who preferred colonoscopy for each study). Twenty-three studies met inclusion criteria, totaling 5616 subjects. In 16 of these studies, patients preferred CTC over colonoscopy, while colonoscopy was preferred in three studies. Due to the high degree of heterogeneity, an overall pooled preference difference was not calculated. Stratified analysis revealed that studies published in radiology journals (preference difference 0.590 [95 % CI 0.485, 0.694]) seemed more likely than studies in gastroenterology (0.218 [-0.015-0.451]) or general medicine journals (-0.158 [-0.389-0.072]) to report preference for CTC (p<0.001). Studies by radiology authors showed a trend towards stronger preference for CTC compared with studies by gastroenterology authors. Symptomatic patients expressed no preference, but screening patients preferred CTC. There was no difference in preferences between studies using "masked" and "unmasked" preference ascertainment methods. Three studies featuring limited bowel preparations for CTC reported marked preference for CTC. There was no evidence of publication bias, while cumulative and exclusion analysis did not show any temporal trend or dominant study. Limitations included data heterogeneity and preference ascertainment limitations. In conclusion, most included studies reported preference for CTC. On stratified analysis, screening patients preferred CTC while diagnostic patients showed no preference. Studies published in radiology journals showed significantly stronger preference for CTC compared with studies in gastroenterology or general medicine journals.

Evaluation of two minimal-preparation regimes for CT colonography: optimising image quality and patient acceptability

OBJECTIVE

To compare a 2 day bowel preparation regime of barium, iodine and a mild stimulant laxative with a 1 day iodine-only regime for CT colonography (CTC).

METHODS

100 consecutive patients underwent CTC. The first 50 patients (Regime 1) ingested 1 bisacodyl tablet twice a day 3 days before CTC and 1 dose each of 50 ml of barium and 20 ml of iodinated contrast per day starting 2 days before CTC. The second 50 patients (Regime 2) ingested 3 doses of iodinated contrast over 24 h prior to CTC. Volumes of residual stool and fluid, and the effectiveness of stool and fluid tagging, were graded according to methods established by Taylor et al (Taylor S, Slaker A, Burling D, Tam E, Greenhalgh R, Gartner L, et al. CT colonography: optimisation, diagnostic performance and patient acceptability of reduced-laxative regimens using barium-based faecal tagging. Eur Radiol 2008; 18: 32-42). A 3 day low-residue diet was taken by both cohorts. Questionnaires rating the side-effects and burden of the bowel preparation were compared to a control cohort of patients undergoing barium enema.

RESULTS

The proportion of colons producing none/scattered stool (score 1) was 90.3% with Regime 1 and 65.0% with Regime 2 (p<0.005). Any residual stool was significantly better tagged with Regime 1 (score 5), with 91.7% of Regime 1 exhibiting optimum tagging vs 71.3% of Regime 2 (p<0.05). No significant differences in side-effects between the bowel preparation regimes for CTC were elicited. Bowel preparation for barium enema was tolerated significantly worse than both of the CTC bowel preparation regimes.

CONCLUSION

Regime 1, containing a 3 day preparation of a mild laxative, barium and iodine, produced a significantly better prepared colon, with no difference in patient acceptability.

National CT colonography trial (ACRIN 6664): comparison of three full-laxative bowel preparations in more than 2500 average-risk patients

OBJECTIVE

The purpose of our study was to compare the effect of three different full-laxative bowel preparations on patient compliance, residual stool and fluid, reader confidence, and polyp detection at CT colonography (CTC).

SUBJECTS AND METHODS

A total of 2531 patients underwent CTC followed by colonoscopy for the American College of Radiology Imaging Network (ACRIN) National CTC Trial. Of this total, 2525 patients used one of three bowel preparations with bisacodyl tablets and stool and fluid tagging: 4 L of polyethylene glycol (PEG); 90 mL of phosphosoda; or 300 mL of magnesium citrate. Patients reported percent compliance with the bowel preparation and radiologists graded each CTC examination for the amount of residual fluid and stool on a scale from 1 (none) to 4 (nondiagnostic). Reader confidence for true-positive findings was reported on a 5-point scale: 1 (low) to 5 (high). Sensitivity and specificity for detecting polyps ≥ 6 mm and ≥ 1 cm compared with colonoscopy were calculated for each preparation.

RESULTS

The most commonly prescribed preparation was phosphosoda (n = 1403) followed by PEG (n = 1020) and magnesium citrate (n = 102). Phosphosoda had the highest patient compliance (p = 0.01), least residual stool (p < 0.001), and highest reader confidence versus PEG for examinations with polyps (p = 0.06). Magnesium citrate had significantly more residual fluid compared with PEG and phosphosoda (p = 0.006). The sensitivity and specificity for detecting colon polyps ≥ 6 mm and ≥ 1 cm did not differ significantly between preparations.

CONCLUSION

Polyp detection was comparable for all three preparations, although phosphosoda had significantly higher patient compliance and the least residual stool.

Colorectal cancer: CT colonography and colonoscopy for detection--systematic review and meta-analysis

PURPOSE

To perform a systematic review and meta-analysis of published studies assessing the sensitivity of both computed tomographic (CT) colonography and optical colonoscopy (OC) for colorectal cancer detection.

MATERIALS AND METHODS

Analysis followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses recommendations. The primary data source was the results of a detailed PubMed search from 1994 to 2009. Diagnostic studies evaluating CT colonography detection of colorectal cancer were assessed by using predefined inclusion and exclusion criteria, in particular requiring both OC and histologic confirmation of disease. Studies that also included a mechanism to assess true-positive versus false-negative diagnoses at OC (eg, segmental unblinding) were used to calculate OC sensitivity. Assessment and data extraction were performed independently by two authors. Potential bias was ascertained by using Quality Assessment of Diagnostic Accuracy Studies guidelines. Specific CT colonography techniques were cataloged. Forest plots of per-patient sensitivity were produced on the basis of random-effect models. Potential bias across primary studies was assessed by using the I(2) statistic. Original study authors were contacted for data clarification when necessary.

RESULTS

Forty-nine studies provided data on 11,151 patients with a cumulative colorectal cancer prevalence of 3.6% (414 cancers). The sensitivity of CT colonography for colorectal cancer was 96.1% (398 of 414; 95% confidence interval [CI]: 93.8%, 97.7%). No heterogeneity (I(2) = 0%) was detected. No cancers were missed at CT colonography when both cathartic and tagging agents were combined in the bowel preparation. The sensitivity of OC for colorectal cancer, derived from a subset of 25 studies including 9223 patients, was 94.7% (178 of 188; 95% CI: 90.4%, 97.2%). A moderate degree of heterogeneity (I(2) = 50%) was present.

CONCLUSION

CT colonography is highly sensitive for colorectal cancer, especially when both cathartic and tagging agents are combined in the bowel preparation. Given the relatively low prevalence of colorectal cancer, primary CT colonography may be more suitable than OC for initial investigation of suspected colorectal cancer, assuming reasonable specificity.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101887/-/DC1.

Reducing the oral contrast dose in CT colonography: evaluation of faecal tagging quality and patient acceptance

AIM

To evaluate the minimal iodine contrast medium load necessary for an optimal computed tomography colonography tagging quality.

MATERIALS AND METHODS

Faecal occult blood test positive patients were randomly selected for one of three iodine bowel preparations: (1) 3 × 50 ml meglumine ioxithalamate (45 g iodine), (2) 4 × 25 ml meglumine ioxithalamate (30 g iodine); or (3) 3 × 25 ml (22.5 g iodine) meglumine ioxithalamate. Two experienced readers assessed the tagging quality per colonic segment on a five-point scale and the presence of adherent stool. Also semi-automatic homogeneity measurements were performed. Patient acceptance was assessed with questionnaires.

RESULTS

Of 70 eligible patients, 45 patients participated (25 males, mean age 62 years). Each preparation group contained 15 patients. The quality of tagging was insufficient (score 1-2) in 0% of segments in group 1; 4% in group 2 (p<0.01 versus group 1); and 5% in group 3 (p=0.06 versus group 1). In group 1 in 11% of the segments adherent stool was present compared with 49% in group 2 and 41% in group 3 (p<0.01, group 2 and 3 versus group 1). Homogeneity was 85, 102 (p<0.01), and 91 SD HU (p=0.26) in groups 1, 2, and 3, respectively. In group 1 two patients experienced no burden after contrast agent ingestion compared to one patient in group 2 and nine patients in group 3 (p=0.017).

CONCLUSION

A dose of 3 × 50 ml meglumine ioxithalamate is advisable for an optimal tagging quality despite beneficial effects on the patient acceptance in patients receiving a lower dose.

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.

Computed tomographic colonography: Hope or hype?

Computed tomographic colonography (CTC) is a promising emerging technology for imaging of the colon. This concise review discusses the currently available data on CTC technique, test characteristics, acceptance, safety, cost-effectiveness, follow-up strategy, and extracolonic findings. In summary, CTC technique is still evolving, and further research is needed to clarify the role of automated colonic insufflation, smooth-muscle relaxants, intravenous and oral contrast, software rendering, and patient positioning. Currently, full bowel preparation is still required to achieve optimal results. The sensitivity for detecting large polyps (> 1 cm) can be as high as 85%, with specificity of up to 97%. These test characteristics are almost comparable to those of conventional colonoscopy. Patient acceptance of CTC is generally higher than that for colonoscopy, especially in patients who have never undergone either procedure. CTC is generally safe, although uncommon instances of colonic perforation have been documented. In terms of cost-effectiveness, most decision analyses have concluded that CTC would only be cost-effective if it were considerably cheaper than conventional colonoscopy. The proper follow-up strategy for small polyps or incidental extracolonic findings discovered during CTC is still under debate. At present, the exact clinical role of virtual colonoscopy still awaits determination. Even though widespread CTC screening is not available today, in the future there may eventually be a role for this technology. Technological advances in this area will undoubtedly continue, with multi-detector row CT scanners allowing thinner collimation and higher resolution images. Stool-tagging techniques are likely to evolve and may eventually allow for low-preparation CTC. Perceptual and fatigue-related reading errors can potentially be minimized with the help of computer-aided detection software. Further research will define the exact role of this promising technology in our diagnostic armamentarium.

Comparative evaluation of the fecal-tagging quality in CT colonography: barium vs. iodinated oral contrast agent

RATIONALE AND OBJECTIVES

The purpose of this evaluation was to compare the tagging quality of a barium-based regimen with that of iodine-based regimens for computed tomographic (CT) colonography.

MATERIALS AND METHODS

Tagging quality was assessed retrospectively in three different types of fecal-tagging CT colonographic cases: 24 barium-based cases, 22 nonionic iodine-based cases, and 24 ionic iodine-based cases. For the purpose of evaluation, the large intestine was divided into six segments, and the tagging homogeneity of a total of 420 segments (70 patients) was graded by three blinded readers from 0 (heterogeneous) to 4 (homogeneous).

RESULTS

For barium-based cases, the average score for the three readers was 2.4, whereas it was 3.4 for nonionic iodine and 3.6 for ionic iodine. The percentages of segments that were assigned scores of 4 (excellent tagging [100%]) were 11.6%, 61.9%, and 72.9% for the barium-based, nonionic iodine-based, and ionic iodine-based regimens, respectively. The homogeneity scores of iodine-based fecal-tagging regimens were significantly higher than those of the barium-based fecal-tagging regimen (P < .001). The CT attenuation values of tagging in the cases were also assessed: the minimum and maximum values were significantly higher for the iodine-based regimens than for the barium-based regimen (P < .001).

CONCLUSIONS

The iodine-based fecal-tagging regimens provide significantly greater homogeneity in oral-tagging fecal material than the barium-based fecal-tagging regimen. Iodine-based fecal-tagging regimens can provide an appropriate method for use in nonlaxative or minimum-laxative CT colonography.