CT colonography polyp matching: differences between experienced readers

Performance of radiographic imaging after incomplete colonoscopy for nonmalignant causes in clinical practice

BACKGROUND AND AIMS

CT colonography (CTC) or barium enema are commonly ordered to complete colorectal imaging after an incomplete colonoscopy. We evaluated the sensitivity of radiographic studies performed for this purpose in clinical practice outside clinical trials.

METHODS

Adult patients referred to an expert endoscopist for incomplete colonoscopy because of a redundant colon or a difficult sigmoid and who underwent previous radiographic imaging between July 2001 and July 2019 were identified. None of the patients had a malignant obstruction as the cause of incomplete colonoscopy. Data on polyp size, location, and pathology were obtained from colonoscopy and radiology reports. Polyps identified on imaging and colonoscopy were matched based on polyp size and location.

RESULTS

Among 769 patients referred for incomplete colonoscopy, we identified 65 with a radiographic examination performed within 36 months of colonoscopy at our center. Per-patient sensitivity for CTC was suboptimal (70%) and was very low for barium enema (26.7%). Per-polyp sensitivity for both CTC and barium enema was poor (23.8% and 7.6%). Quality of the examination did not seem to affect procedure sensitivity.

CONCLUSIONS

Radiographic imaging after incomplete colonoscopy for reasons other than malignant obstruction had poor sensitivity for polyps. Patients with incomplete colonoscopies should be considered for repeat colonoscopy by an expert.

British Society of Gastroenterology/Association of Coloproctology of Great Britain and Ireland/Public Health England post-polypectomy and post-colorectal cancer resection surveillance guidelines

These consensus guidelines were jointly commissioned by the British Society of Gastroenterology (BSG), the Association of Coloproctology of Great Britain and Ireland (ACPGBI) and Public Health England (PHE). They provide an evidence-based framework for the use of surveillance colonoscopy and non-colonoscopic colorectal imaging in people aged 18 years and over. They are the first guidelines that take into account the introduction of national bowel cancer screening. For the first time, they also incorporate surveillance of patients following resection of either adenomatous or serrated polyps and also post-colorectal cancer resection. They are primarily aimed at healthcare professionals, and aim to address:Which patients should commence surveillance post-polypectomy and post-cancer resection?What is the appropriate surveillance interval?When can surveillance be stopped? two or more premalignant polyps including at least one advanced colorectal polyp (defined as a serrated polyp of at least 10 mm in size or containing any grade of dysplasia, or an adenoma of at least 10 mm in size or containing high-grade dysplasia); or five or more premalignant polyps The Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument provided a methodological framework for the guidelines. The BSG's guideline development process was used, which is National Institute for Health and Care Excellence (NICE) compliant.two or more premalignant polyps including at least one advanced colorectal polyp (defined as a serrated polyp of at least 10 mm in size or containing any grade of dysplasia, or an adenoma of at least 10 mm in size or containing high-grade dysplasia); or five or more premalignant polyps The key recommendations are that the high-risk criteria for future colorectal cancer (CRC) following polypectomy comprise either:two or more premalignant polyps including at least one advanced colorectal polyp (defined as a serrated polyp of at least 10 mm in size or containing any grade of dysplasia, or an adenoma of at least 10 mm in size or containing high-grade dysplasia); or five or more premalignant polyps This cohort should undergo a one-off surveillance colonoscopy at 3 years. Post-CRC resection patients should undergo a 1 year clearance colonoscopy, then a surveillance colonoscopy after 3 more years.

Evolution of Screen-Detected Small (6-9 mm) Polyps After a 3-Year Surveillance Interval: Assessment of Growth With CT Colonography Compared With Histopathology

OBJECTIVES

Volumetric growth assessment has been proposed for predicting advanced histology at surveillance computed tomography (CT) colonography (CTC). We examined whether is it possible to predict which small (6-9 mm) polyps are likely to become advanced adenomas at surveillance by assessing volumetric growth.

METHODS

In an invitational population-based CTC screening trial, 93 participants were diagnosed with one or two 6-9 mm polyps as the largest lesion(s). They were offered a 3-year surveillance CTC. Participants in whom surveillance CTC showed lesion(s) of ≥6 mm were offered colonoscopy. Volumetric measurements were performed on index and surveillance CTC, and polyps were classified into growth categories according to ±30% volumetric change (>30% growth as progression, 30% growth to 30% decrease as stable, and >30% decrease as regression). Polyp growth was related to histopathology.

RESULTS

Between July 2012 and May 2014, 70 patients underwent surveillance CTC after a mean surveillance interval of 3.3 years (s.d. 0.3; range 3.0-4.6 years). In all, 33 (35%) of 95 polyps progressed, 36 (38%) remained stable, and 26 (27%) regressed, including an apparent resolution in 13 (14%) polyps. In 68 (83%) of the 82 polyps at surveillance, histopathology was obtained; 15 (47%) of 32 progressing polyps were advanced adenomas, 6 (21%) of 28 stable polyps, and none of the regressing polyps.

CONCLUSIONS

The majority of 6-9 mm polyps will not progress to advanced neoplasia within 3 years. Those that do progress to advanced status can in particular be found among the lesions that increased in size on surveillance CTC.

Computer tomography colonography participation and yield in patients under surveillance for 6-9 mm polyps in a population-based screening trial

Purpose

Surveillance CT colonography (CTC) is a viable option for 6-9 mm polyps at CTC screening for colorectal cancer. We established participation and diagnostic yield of surveillance and determined overall yield of CTC screening.

Material and methods

In an invitational CTC screening trial 82 of 982 participants harboured 6-9 mm polyps as the largest lesion(s) for which surveillance CTC was advised. Only participants with one or more lesion(s) ≥6 mm at surveillance CTC were offered colonoscopy (OC); 13 had undergone preliminary OC. The surveillance CTC yield was defined as the number of participants with advanced neoplasia in the 82 surveillance participants, and was added to the primary screening yield.

Results

Sixty-five of 82 participants were eligible for surveillance CTC of which 56 (86.2 %) participated. Advanced neoplasia was diagnosed in 15/56 participants (26.8 %) and 9/13 (69.2 %) with preliminary OC. Total surveillance yield was 24/82 (29.3 %). No carcinomas were detected. Adding surveillance results to initial screening CTC yield significantly increased the advanced neoplasia yield per 100 CTC participants (6.1 to 8.6; p < 0.001) and per 100 invitees (2.1 to 2.9; p < 0.001).

Conclusion

Surveillance CTC for 6-9 mm polyps has a substantial yield of advanced adenomas and significantly increased the CTC yield in population screening.

Key Points

• The participation rate in surveillance CT colonography (CTC) is 86 %.

• Advanced adenoma prevalence in a 6-9 mm CTC surveillance population is high.

• Surveillance CTC significantly increases the yield of population screening by CTC.

• Surveillance CTC for 6-9 mm polyps is a safe strategy.

• Surveillance CTC is unlikely to yield new important extracolonic findings.

Training readers to improve their accuracy in grading Crohn's disease activity on MRI

OBJECTIVES

To prospectively evaluate if training with direct feedback improves grading accuracy of inexperienced readers for Crohn's disease activity on magnetic resonance imaging (MRI).

METHODS

Thirty-one inexperienced readers assessed 25 cases as a baseline set. Subsequently, all readers received training and assessed 100 cases with direct feedback per case, randomly assigned to four sets of 25 cases. The cases in set 4 were identical to the baseline set. Grading accuracy, understaging, overstaging, mean reading times and confidence scores (scale 0-10) were compared between baseline and set 4, and between the four consecutive sets with feedback. Proportions of grading accuracy, understaging and overstaging per set were compared using logistic regression analyses. Mean reading times and confidence scores were compared by t-tests.

RESULTS

Grading accuracy increased from 66 % (95 % CI, 56-74 %) at baseline to 75 % (95 % CI, 66-81 %) in set 4 (P = 0.003). Understaging decreased from 15 % (95 % CI, 9-23 %) to 7 % (95 % CI, 3-14 %) (P < 0.001). Overstaging did not change significantly (20 % vs 19 %). Mean reading time decreased from 6 min 37 s to 4 min 35 s (P < 0.001). Mean confidence increased from 6.90 to 7.65 (P < 0.001). During training, overall grading accuracy, understaging, mean reading times and confidence scores improved gradually.

CONCLUSIONS

Inexperienced readers need training with at least 100 cases to achieve the literature reported grading accuracy of 75 %.

KEY POINTS

• Most radiologists have limited experience of grading Crohn's disease activity on MRI. • Inexperienced readers need training in the MRI assessment of Crohn's disease. • Grading accuracy, understaging, reading time and confidence scores improved during training. • Radiologists and residents show similar accuracy in grading Crohn's disease. • After 100 cases, grading accuracy can be reached as reported in the literature.

The feasibility of colorectal cancer detection using dual-energy computed tomography with iodine mapping

AIM

To assess the feasibility of colorectal cancer detection using dual-energy computed tomography with iodine mapping and without bowel preparation or bowel distension.

MATERIALS AND METHODS

Consecutive patients scheduled for preoperative staging computed tomography (CT) because of diagnosed or high suspicion for colorectal cancer were prospectively included in the study. A single contrast-enhanced abdominal CT acquisition using dual-source mode (100 kV/140 kV) was performed without bowel preparation. Weighted average 120 kV images and iodine maps were created with post-processing. Two observers performed a blinded read for colorectal lesions after being trained on three colorectal cancer patients. One observer performed an unblinded read for lesion detectability and placed a region of interest (ROI) within each lesion.

RESULTS

In total 21 patients were included and 18 had a colorectal cancer at the time of the CT acquisition. Median cancer size was 43 mm [interquartile range (IQR) 27-60 mm] and all 18 colorectal cancers were visible on the 120 kV images and iodine map during the unblinded read. During the blinded read, observers found 90% (27/30) of the cancers with 120 kV images only and 96.7% (29/30) after viewing the iodine map in addition (p = 0.5). Median enhancement of colorectal cancers was 29.9 HU (IQR 23.1-34.6). The largest benign lesions (70 and 25 mm) were visible on the 120 kV images and iodine map, whereas four smaller benign lesions (7-15 mm) were not.

CONCLUSION

Colorectal cancers are visible on the contrast-enhanced dual-energy CT without bowel preparation or insufflation. Because of the patient-friendly nature of this approach, further studies should explore its use for colorectal cancer detection in frail and elderly patients.

Computer-aided detection of colorectal polyps in CT colonography with and without fecal tagging: a stand-alone evaluation

PURPOSE

To evaluate the stand-alone performance of a computer-aided detection (CAD) algorithm for colorectal polyps in a large heterogeneous CT colonography (CTC) database that included both tagged and untagged datasets.

METHODS

Written, informed consent was waived for this institutional review board-approved, HIPAA-compliant retrospective study. CTC datasets from 2063 patients were assigned to training (n = 374) and testing (n = 1689). The test set consisted of 836 untagged and 853 tagged examinations not used for CAD training. Examinations were performed at 15 sites in the United States, Asia, and Europe, using 4- to 64-multidetector-row computed tomography and various acquisition parameters. CAD sensitivities were calculated on a per-patient and per-polyp basis for polyps measuring ≥6 mm. The reference standard was colonoscopy in 1588 (94%) and consensus interpretation by expert radiologists in 101 (6%) patients. Statistical testing employed χ, logistic regression, and Mann-Whitney U tests.

RESULTS

In 383 of 1689 individuals, 564 polyps measuring ≥6 mm were identified by the reference standard (347 polyps: 6-9 mm and 217 polyps: ≥10 mm). Overall, CAD per-patient sensitivity was 89.6% (343/383), with 89.0% (187/210) for untagged and 90.2% (156/173) for tagged datasets (P = 0.72). Overall, per-polyp sensitivity was 86.9% (490/564), with 84.4% (270/320) for untagged and 90.2% (220/244) for tagged examinations (P = 068). The mean false-positive rate per patient was 5.14 (median, 4) in untagged and 4.67 (median, 4) in tagged patient datasets (P = 0.353).

CONCLUSION

Stand-alone CAD can be applied to both tagged and untagged CTC studies without significant performance differences. Detection rates are comparable to human readers at a relatively low false-positive rate, making CAD a useful tool in clinical practice.

Evaluation of a standardized CT colonography training program for novice readers

PURPOSE

To determine how many computed tomographic (CT) colonography training studies have to be evaluated by novice readers to obtain an adequate level of competence in polyp detection.

MATERIALS AND METHODS

The study was approved by the Institutional Review Board. Informed consent was obtained from all participants. Six physicians (one radiologist, three radiology residents, two researchers) and three technicians completed a CT colonography training program. Two hundred CT colonographic examinations with colonoscopic verification were selected from a research database, with 100 CT colonographic examinations with at least one polyp 6 mm or larger. After a lecture session and short individual hands-on training, CT colonography training was done individually with immediate feedback of colonoscopy outcome. Per-polyp sensitivity was calculated for four sets of 50 CT colonographic examinations for lesions 6 mm or larger. By using logistic regression analyses, the number of CT colonographic examinations to reach 90% sensitivity for lesions 6 mm or larger was estimated. Reading times were registered.

RESULTS

The average per-polyp sensitivity for lesions 6 mm or larger was 76% (207 of 270) in the first set of 50 CT colonographic examinations, 77% (262 of 342) in the second (P = .96 vs first set), 80% (310 of 387) in the third (P = .67 vs first set), and 91% (261 of 288) in the fourth (P = .018). The estimated number of CT colonographic examinations for a sufficient sensitivity was 164. Six of nine readers reached this level of competence within 175 CT colonographic examinations. Reading times decreased significantly from the first to the second set of 50 CT colonographic examinations for six readers.

CONCLUSION

Novice CT colonography readers obtained sensitivity equal to that of experienced readers after practicing on average 164 CT colonographic studies.

Positive predictive value for polyps detected at screening CT colonography

PURPOSE

To determine the positive predictive value (PPV) for polyps detected at CT colonography (CTC).

METHODS

Assessment of 739 colorectal lesions >or=6 mm detected prospectively at CTC screening in 479 patients was performed. By-polyp PPV was analyzed according to small (6-9 mm) versus large (>or=10 mm) size; morphology (sessile/pedunculated/flat); diagnostic confidence level (3 = most confident, 1 = least confident); and histology. By-patient PPV was analyzed at various polyp size thresholds.

RESULTS

By-polyp PPV for CTC-detected lesions >or=6 mm, 6-9 mm, and >or=10 mm was 91.6% (677/739), 90.1% (410/451), and 92.7% (267/288), respectively (p = 0.4). By-polyp PPV according to sessile, pedunculated, flat, and mass-like morphology was 92.5% (441/477), 96.5% (139/144), 77.7% (73/94), and 97.6% (40/41), respectively (p < 0.0001 for flat versus polypoid morphology). By-polyp PPV according to diagnostic confidence level was 94.7% (554/585) for highest (= level 3), 83.5% (106/127) for intermediate (= level 2), and 63.0% (17/27) for lowest (= level 1) confidence (p < 0.0001 for levels-2/3 versus level-1). By-patient PPV at 6-mm, 8-mm, 10-mm, and 30-mm polyp size thresholds was 92.3% (442/479), 93.0% (306/329), 93.1% (228/245), and 97.4% (38/39), respectively.

CONCLUSION

The overall per-polyp and per-patient PPV for lesions >or=6 mm was 92% for CTC screening. Increased diagnostic confidence and polypoid (non-flat) morphology correlated with a higher PPV, whereas small versus large polyp size had very little effect.