Virtual colonoscopy

A computer-graphics-based alternative to conventional optical colonoscopy, known as virtual colonoscopy (VC) or computed tomography colonography (CTC), is rapidly gaining popularity. During this procedure, which was concurrently developed by our group at Stony Brook University [5] and by other researchers [10], the distended colon is imaged by a helical or multislice CT scanner. The acquired abdominal CT scan commonly consists of 350--750 axial images of 512x512 sub-millimeter resolution, providing excellent contrast between the colon wall and the lumen. A 3D model of the colon is then reconstructed from the CT scan by automatically segmenting the colon out of the rest of the abdomen and employing an electronic cleansing algorithm for computer-based removal of the residual material. The PC-based visualization software employs volume rendering and allows the user, typically a physician, to interactively navigate through the virtual 3D model of the colon. An intuitive user interface with customized tools supports measurements and virtual biopsy to inspect suspicious regions. Unlike optical colonoscopy (see the sidebar "Conventional Colorectal Cancer Screening"), VC is patient friendly since the patient undergoes less rigorous preparation prior to the procedure. VC is also a fast, noninvasive, highly accurate, cost-effective method for mass screening of colon polyps.