Virtual colonoscopy for colorectal polyp detection

CT colonography is a new technique that uses volumetric CT data combined with advanced imaging software to create 2D and 3D images of the colon. Our technique uses both 3D images that simulate the endoluminal perspective of the colonoscope as well as axial and reformatted 2D images. 2D and 3D images are complementary and when combined offer the most robust performance for the detection of colorectal polyps. Currently, CT examinations are performed in the fully cleansed and air-inflated colon using a slice thickness = 5 mm, reconstruction interval = 3 mm, pitch = 1.3, mA = 70. The sensitivity for the detection of polyps superior or equal to 1 cm is 75%, and the specificity 90%. The most commonly encountered problems include retained colonic fluid and stool, suboptimally distended colonic segments, and long interpretation times. Many of these problems can be solved by using both supine and prone imaging. It is expected that the performance of this examination will improve and a new era of colorectal screening will begin.