Detailed quantitative assessment of colonic morphology at CT colonography using novel software: a feasibility and reproducibility study

Abstract

The aim of this study was to evaluate feasibility and reproducibility of quantitative assessment of colonic morphology on CT colonography (CTC). CTC datasets from 60 patients with optimal colonic distension were assessed using prototype software. Metrics potentially associated with poor endoscopic performance were calculated for the total colon and each segment including: length, volume, tortuosity (number of high curvature points <90°), and compactness (volume of box containing centerline divided by centerline length). Sigmoid apex height relative to the lumbosacral junction was also measured. Datasets were quantified twice each, and intra-reader reliability was evaluated using concordance correlation coefficient and Bland–Altman plot. Complete quantitative datasets including the five proposed metrics were generated from 58 of 60 (97 %) CTC examinations. The sigmoid and transverse segments were the longest (55.9 and 51.4 cm), had the largest volumes (0.410 and 0.609 L), and were the most tortuous (3.39 and 2.75 high curvature points) and least compact (3347 and 3595 mm²), noting high inter-patient variability for all metrics. Mean height of the sigmoid apex was 6.7 cm, also with high inter-patient variability (SD 6.8 cm). Intra-reader reliability was high for total and segmental lengths and sigmoid apex height (CCC = 0.9991) with excellent repeatability coefficient (CR = 3.0–3.3). There was low percent variance of metrics dependent upon length (median 5 %). Detailed automated quantitative assessment of colonic morphology on routine CTC datasets is feasible and reproducible, requiring minimal reader interaction.

Appendices

Appendix 1

All patients underwent a complete colon preparation in a standard fashion. The preparation was tailored to the patient and included 3–7 days of low-residue diet followed by 24–48 h of clear liquids. Colonic cleansing was accomplished with using 238 g MiraLAX in 64 oz fluid and four Dulcolax tablets the day before the examination, and one Dulcolax suppository the morning of the examination. For fecal tagging, Tagitol™ 5 Barium Sulfate suspension (Bracco Diagnostics, Monroe Township, NJ, USA) 20-ml bottle each was given with the last three solid meals. All studies were performed at our institution on a Siemens 64-slice CT scanner with 1-mm axial thin section reconstructed images used for quantification. Colonic distention was achieved using an automated CO₂ insufflator (PROTOCO₂L Colon Insufflator, Bracco Diagnostics, Monroe Township, NJ, USA). Adequacy of distention was judged by the attending radiologist monitoring the examination. The patients were scanned in the supine and prone positions. Additional lateral decubitus views were obtained when necessary.

Appendix 2

The anatomic definitions used for manual segmentation were as follows:

• Rectum/sigmoid junction: point where the colon passed from the subperitoneal rectal segment into the peritoneal cavity.

• Sigmoid/descending colon junction: point where the descending colon passed from the retroperitoneum into the peritoneal cavity corresponding to the point where the descending colon coursed ventrally in the sagittal view and medially in the coronal view.

• Descending/transverse colon and transverse/ascending colon junctions: most superior points within the splenic and hepatic flexures, respectively.

• Ascending colon/cecum junction: first haustral fold distal to the ileocecal valve.