TECHNICAL FACTORS OF CT ANGIOGRAPHY STUDIED WITH A CAROTID-ARTERY PHANTOM

PURPOSE: To evaluate scanning parameters (conventional versus spiral C T, section thickness, and pitch) and vessel orientation in the perform ance of CT angiography, METHODS: Conventional CT and 1.0-, 1.5-, and 2 .0-pitch spiral CT acquisitions of a carotid phantom designed with ves sels oriented parallel to the z-axis, 45 degrees oblique, and perpendi cular to the z-axis were obtained with section thicknesses of 2, 4, an d 8 mm. The phantom contained 32 vessels with 0% to 100% stenoses, Nor mal and stenotic luminal diameters were measured and the number of art ifacts was assessed, RESULTS: No overall difference was observed among conventional and spiral CT acquisitions obtained with pitches of 1.0, 1.5, and 2.0. With thicker sections, CT angiographic accuracy decreas ed and artifacts increased. The three-vessel orientations were relativ ely comparable in accuracy in terms of the percentage of stenosis meas ured. Vessels parallel to the z-axis suffered less artifactual degrada tion. Unique artifacts, such as luminal distortion and beam hardening, were observed in vessels oriented at 45 degrees and perpendicular to the z-axis. CONCLUSION: Use of thinner sections with vessels oriented parallel to the z-axis optimizes CT angiographic quality. There is no apparent degradation with the use of spiral CT, and a pitch of 1.5 or 2.0 provides results equivalent to 1.0-pitch spiral studies.