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An initial experience with screening for colon polyps using spiral CT with and without CT colography (virtual
D K Rex1, D Vining, K K Kopecky
1Department of Medicine, Indiana University School of Medicine, Indianapolis, USA.
Gastrointestinal Endoscopy
|August 27, 1999
Summary
Computed tomographic (CT) colography, or virtual colonoscopy, shows limited sensitivity for detecting colon polyps, especially smaller ones. This imaging method is not yet adequate for colorectal cancer screening.
Area of Science:
- Medical Imaging
- Gastroenterology
- Oncology
Background:
- Computed tomographic (CT) colography, also known as virtual colonoscopy, is an emerging imaging technique for identifying colon polyps and cancer.
- The study investigates the effectiveness of this new method in a real-world setting.
Purpose of the Study:
- To assess the sensitivity of CT colography in detecting colon polyps within an asymptomatic population.
- To compare the diagnostic performance of different CT colography visualization techniques.
Main Methods:
- Forty-six asymptomatic individuals underwent spiral CT followed by same-day colonoscopy.
- Images were reviewed using two-dimensional axial, multiplanar, and three-dimensional (3D) CT colography techniques (surface and volume rendering).
- Radiologists were blinded to colonoscopic findings.
Main Results:
- Three-dimensional CT colography demonstrated superior polyp detection compared to two-dimensional imaging.
- Sensitivity varied by polyp size: 25% for ≥2 cm, 60% for 1-1.9 cm, 43% for 6-9 mm, and 11% for ≤5 mm.
- Specificity for adenomas ≥1 cm was 89%; however, large, flat right-sided adenomas were challenging to detect, and perceptual errors were common.
Conclusions:
- CT colography, as performed in this study, is not sufficient as a colorectal cancer screening tool.
- Meticulous bowel preparation and adequate colonic distention are critical for accurate interpretation.
- Several technical factors influencing CT colography performance were identified.