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U sing helical CT data and advanced imaging software, CT colonogra-phy provides a complete colorectal examination with minimal patient risk or dis-comfort. Unlike two-dimensional(2D) axial CT images that are perpendicular to the patient’s midline, reformatted 2D CT colonography images are produced at cross sections and orthogonal angles to the colon midline. Threedimensional(3D) CT colonography is a perspective intraluminal imaging technique that simulates an endoscopic view. Preliminary results using CT colonography have been promising for detecting colorectal cancer and polyps 11-41. but clinical usefulness is limited by lengthy image processing times and data storage requirements. An important factor contributing to suboptimal efficiency is the large data size, generally 400-500 I-mm-thick CT images per examination. Data size could be reduced by implementing a faster pitch or larger …