Primary uncleansed 2D versus primary electronically cleansed 3D in limited bowel preparation CT-colonography. Is there a difference for novices and experienced readers?

Diagnostic accuracy of computed tomography colonography in patients at high risk for colorectal cancer: a meta-analysis

AIM

The aim was to explore the diagnostic value of computed tomographic colonography (CTC) compared with conventional colonoscopy in individuals at high risk for colorectal cancer.

METHOD

PubMed, Embase, the Cochrane Library and the Web of Science were searched by two independent reviewers for potentially eligible studies published up to 31 October 2018 that were based on a per-patient analysis. stata, meta-disc and revman were used to perform this meta-analysis. A random-effect model was used, and a subgroup analysis was conducted to explore the sources of heterogeneity.

RESULTS

A total of 14 full-text articles, involving 3578 patients, were included in this meta-analysis. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio and the area under the summary receiver operating characteristic curve of CTC for detecting polyps ≥ 6 mm were 0.87 (95% CI 0.83-0.90), 0.90 (95% CI 0.86-0.93), 9.08 (95% CI 6.28-13.13), 0.14 (95% CI 0.11-0.18) and 0.94 (95% CI 0.92-0.96), respectively. For polyps ≥ 10 mm, the pooled sensitivity, specificity, positive likelihood ratio and negative likelihood ratio of CTC were 0.91 (95% CI 0.86-0.94), 0.98 (95% CI 0.95-0.99), 40.36 (95% CI 19.16-85.03), 0.90 (95% CI 0.06-0.14) and 0.98 (95% CI 0.96-0.99), respectively.

CONCLUSION

In this meta-analysis, CTC had high diagnostic accuracy for detecting polyps ≥ 6 mm and ≥ 10 mm in patients at high risk of developing colorectal cancer and it had a higher sensitivity and specificity for detecting polyps ≥ 10 mm than polyps ≥ 6 mm. However, the results should be used cautiously due to the significant heterogeneity.

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.

Comparing the diagnostic yields of technologists and radiologists in an invitational colorectal cancer screening program performed with CT colonography

PURPOSE

To compare the diagnostic yields of a radiologist and trained technologists in the detection of advanced neoplasia within a population-based computed tomographic (CT) colonography screening program.

MATERIALS AND METHODS

Ethical approval was obtained from the Dutch Health Council, and written informed consent was obtained from all participants. Nine hundred eighty-two participants (507 men, 475 women) underwent low-dose CT colonography after noncathartic bowel preparation (iodine tagging) between July 13, 2009, and January 21, 2011. Each scan was evaluated by one of three experienced radiologists (≥800 examinations) by using primary two-dimensional (2D) reading followed by secondary computer-aided detection (CAD) and by two of four trained technologists (≥200 examinations, with colonoscopic verification) by using primary 2D reading followed by three-dimensional analysis and CAD. Immediate colonoscopy was recommended for participants with lesions measuring at least 10 mm, and surveillance was recommended for participants with lesions measuring 6-9 mm. Consensus between technologists was achieved in case of discordant recommendations. Detection of advanced neoplasia (classified by a pathologist) was defined as a true-positive (TP) finding. Relative TP and false-positive (FP) fractions were calculated along with 95% confidence intervals (CIs).

RESULTS

Overall, 96 of the 982 participants were referred for colonoscopy and 104 were scheduled for surveillance. Sixty of 84 participants (71%) referred for colonoscopy by the radiologist had advanced neoplasia, compared with 55 of 64 participants (86%) referred by two technologists. Both the radiologist and technologists detected all colorectal cancers (n = 5). The relative TP fraction (for technologists vs radiologist) for advanced neoplasia was 0.92 (95% CI: 0.78, 1.07), and the relative FP fraction was 0.38 (95% CI: 0.21, 0.67).

CONCLUSION

Two technologists serving as a primary reader of CT colonographic images can achieve a comparable sensitivity to that of a radiologist for the detection of advanced neoplasia, with far fewer FP referrals for colonoscopy.

Diagnostic value of CT-colonography as compared to colonoscopy in an asymptomatic screening population: a meta-analysis

Objectives

Previous meta-analyses on CT-colonography included both average and high risk individuals, which may overestimate the diagnostic value in screening. A meta-analysis was performed to obtain the value of CT-colonography for screening.

Methods

A search was performed using PubMed, Embase and Cochrane. Article selection and critical appraisal was done by two reviewers. Inclusion criteria: prospective, randomized trials or cohort studies comparing CT-colonography with colonoscopy (≥50 participants), ≥95% average risk participants ≥50 years. Study characteristics and 2 × 2 contingency Tables were recorded. Sensitivity and specificity estimates were calculated per patient and per polyp (≥6 mm, ≥10 mm), using univariate and bivariate analyses.

Results

Five of 1,021 studies identified were included, including 4,086 participants (<1% high risk). I²-values showed substantial heterogeneity, especially for 6–9 mm polyps and adenomas: 68.1% vs. 78.6% (sensitivity per patient). Estimated sensitivities for patients with polyps or adenomas ≥ 6 mm were 75.9% and 82.9%, corresponding specificities 94.6% and 91.4%. Estimated sensitivities for patients with polyps or adenomas ≥ 10 mm were 83.3% and 87.9%, corresponding specificities 98.7% and 97.6%. Estimated sensitivities per polyp for advanced adenomas ≥ 6 mm and ≥ 10 mm were 83.9% and 83.8%.

Conclusion

Compared to colonoscopy, CT-colonography has a high sensitivity for adenomas ≥ 10 mm. For (advanced) adenomas ≥ 6 mm sensitivity is somewhat lower.

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.

Bowel preparation in CT colonography: electrolyte and renal function disturbances in the frail and elderly patient

PURPOSE

Elderly patients are at increased risk of biochemical disturbances secondary to cathartic medications. This study investigates the renal function, electrolyte and clinical disturbances associated with CT colonography (CTC) with sodium picosulphate-magnesium citrate (SPS-MC) in a subgroup of frail, elderly patients.

METHODS

Patients aged over 70 years considered at risk of complication during SPS-MC administration by a physician specialised in care of the elderly were included in this retrospective study. Biochemical parameters pre- and post-CTC and the presence of co-morbidities were recorded. Imaging findings and quality of bowel preparation at CTC were graded by consensus by two radiologists.

RESULTS

Of the 72 patients 56% had co-morbidities that caution the use of SPS-MC. No significant changes in serum urea, sodium, potassium or estimated glomerular filtration rate (eGFR) occurred post-CTC (p > 0.10). Serum magnesium increased by 0.11 mmol/L in 14 patients (p = 0.03) without clinical sequelae. Good overall preparation was achieved in 88% of patients, allowing confident identification of signs of colonic neoplasia in 20 patients (27%). A mild increase in serum magnesium but no other significant biochemical disturbance was observed.

CONCLUSION

In our group CTC with SPS-MC was safe and effective; however, we advise an alternate preparation be considered in patients with decreased renal function due to decreased magnesium clearance.