Virtual computed tomography colonoscopy: artifacts, image quality and radiation dose load in a cadaver study

The purpose of our study was to evaluate the interdependency of spatial res olution image reconstruction artifacts, and radiation doses in virtual CT c olonoscopy by comparing various CT scanning protocols. A pig's colon with S everal artificial polypoid lesions was imaged after air insufflation with h elical CT scanning using 1-, 3-, and 5-mm collimation, and pitch values var ying from 1.0 to 3.0. Virtual endoscopic images and "fly through" sequences were calculated on a Sun Spare 20 workstation (Navigator Software, GE Medi cal Systems, Milwaukee, Wis.). Several reconstruction artifacts as well as overall image quality were evaluated by three independent reviewers. In add ition, radiation doses for the different CT-protocols were measured as mult iple-scan average dose using a 10-cm ion chamber and a standard Plexiglass body phantom. Generally, image quality and reconstruction artifacts were le ss affected by pitch values than by beam collimation. Thus, narrow beam col limation at higher pitch values (e.g. 3 mm/ 2.0) seems to be a reasonable c ompromise between quality of virtual endoscopic images and radiation dose l oad.