CT colonography: size reduction of submerged colorectal polyps due to electronic cleansing and CT-window settings

• Published in: European radiology Vol. 28; no. 11; pp. 4766 - 4774
• Main Authors: Bräuer, Christian, Lefere, Philippe, Gryspeerdt, Stefaan, Ringl, Helmut, Al-Mukhtar, Ali, Apfaltrer, Paul, Berzaczy, Dominik, Füger, Barbara, Furtner, Julia, Müller-Mang, Christina, Pones, Matthias, Scharitzer, Martina, Woitek, Ramona, Graser, Anno, Weber, Michael, Mang, Thomas
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.11.2018; Springer Nature B.V
• Subjects: Aged; Algorithms; Analysis of Variance; Colon; Colonic Polyps - diagnostic imaging; Colonography, Computed Tomographic - methods; Colonography, Computed Tomographic - standards; Computed tomography; Confidence intervals; Diagnostic Radiology; Female; Gastrointestinal; Humans; Image Processing, Computer-Assisted - methods; Imaging; Internal Medicine; Interventional Radiology; Male; Medical screening; Medicine; Medicine & Public Health; Middle Aged; Neuroradiology; Patients; Polyps; Radiology; Reference Standards; Retrospective Studies; Sensitivity and Specificity; Size reduction; Statistical analysis; Ultrasound; Variance analysis; Virtual colonoscopy; Neoplasms, colorectal; Colonic polyps; CT colonography; Cancer screening
• ISSN: 0938-7994; 1432-1084
• DOI: 10.1007/s00330-018-5416-0

Objectives To assess whether electronic cleansing (EC) of tagged residue and different computed tomography (CT) windows influence the size of colorectal polyps in CT colonography (CTC). Methods A database of 894 colonoscopy-validated CTC datasets of a low-prevalence cohort was retrospectively reviewed to identify patients with polyps ≥6 mm that were entirely submerged in tagged residue. Ten radiologists independently measured the largest diameter of each polyp, two-dimensionally, before and after EC in colon, bone, and soft-tissue-windows, in randomised order. Differences in size and polyp count before and after EC were calculated for size categories ≥6 mm and ≥10 mm. Statistical testing involved 95% confidence interval, intraclass correlation and mixed-model ANOVA. Results Thirty-seven patients with 48 polyps were included. Mean polyp size before EC was 9.8 mm in colon, 9.9 mm in bone and 8.2 mm in soft-tissue windows. After EC, the mean polyp size decreased significantly to 9.4 mm in colon, 9.1 mm in bone and 7.1 mm in soft-tissue windows. Compared to unsubtracted colon windows, EC, performed in colon, bone and soft-tissue windows, led to a shift of 6 (12,5%), 10 (20.8%) and 25 (52.1%) polyps ≥6 mm into the next smaller size category, thus affecting patient risk stratification. Conclusions EC and narrow CT windows significantly reduce the size of polyps submerged in tagged residue. Polyp measurements should be performed in unsubtracted colon windows. Key Points • EC significantly reduces the size of polyps submerged in tagged residue. • Abdominal CT-window settings significantly underestimate 2D sizes of submerged polyps. • Size reduction in EC is significantly greater in narrow than wide windows. • Underestimation of polyp size due to EC may lead to inadequate treatment. • Polyp measurements should be performed in unsubtracted images using a colon window.