Automated CO₂ insufflation and image quality in CT colonography

CT colonography is an established technique for detecting polyps and colorectal cancer, particularly in patients unable to undergo conventional colonoscopy. The aim of this study was to evaluate the volume of automated CO₂ insufflation, radiation dose, and diagnostic image quality in patients undergoing CT colonography.

This single-centre retrospective study included patients referred for CT colonography following incomplete or contraindicated colonoscopy. Examinations were performed in supine and prone positions. Radiation dose for each position was collected, including CT dose index volume (CTDI) and dose-length product (DLP). Colonic distention was graded from radiology reports by four radiologists using a five-point Likert scale (1 = poor, 5 = excellent); examinations were classified as diagnostic or non-diagnostic. Statistical analysis examined the association between CO₂ insufflation volume and image quality.

A total of 243 CT colonography examinations (188 women, 55 men; median age 71 years) were analysed. The median CO₂ insufflation volume was 6 L (range 1.5-16 L). Median total DLP was 594 mGy cm (IQR 438.8-866.1). Overall, 222 examinations (91.4%) were considered diagnostic, while 21 (8.6%) were non-diagnostic. Colonic distention was rated as excellent in 131 cases (53.9%), good in 25 (10.3%), sufficient in 41 (16.9%), suboptimal in 35 (14.4%), and poor in 11 (4.5%).

A median of 6 L of CO₂ was used to achieve diagnostic colonic distention, with a median radiation dose of 594 mGy cm. Most examinations in the study achieved an image quality score of 4 or higher, sufficient for accurate interpretation.

Higher-than-expected CO₂ volumes were observed, highlighting the importance of optimizing insufflation protocols to balance image quality, and standardization in clinical practice.