Abstract 2571: Quantitative Analysis of Cobalt Alloy Clip Artifacts in 64 channel Three Dimensional CT Angiography and Introducing Strategies for Minimizing Metallic Artifacts
Objective Clip artifacts on postoperative CT scans after aneurysmal clipping, can create confusion, especially in cases of cobalt alloy clips. Mathematic analysis of the parameters influencing the degree of clip artifact in 64-channel 3 dimensional CT angiography (3D CTA) was conducted to develop methods for minimizing metallic artifacts.
Materials and Methods CT images from 60 cases with single straight Sugita cobalt alloy clips (Mizuho Ikakogyo Co., Tokyo) were analyzed. The degree of the angle between the imaging acquisition gantry angle and clip blade on the CT axial scan (x, y) and on the lateral scout view (z) was measured as independent variables. The length of the clip blade was also measured. Analysis of whether the spring of the clip was included in the 5mm thick scan slide was performed. The dependent variables were the maximal diameter of the white artifact, degree of the symmetrical angle of the streak artifact and the maximal diameter of clip artifact in 3D volume rendering. Univariate and multivariate analysis was conducted to elucidate relationship between each parameters and each type of clip artifacts.
Results The degree of the angle between z axis and clip blade was negatively correlated with the amount of white artifact (p<0.0001, R=-0.589) and positively with the streak artifact (angle of the streak artifact: p<0.0001, R=0.636; number of the streak artifact: p<0.0001, R=0.505). When the spring of the clip was included parallel in scan section, the amount of white artifact was increased (p<0.0001). On multiple linear regression analysis, angle of clip blade to z axis was the major parameter influencing all kinds of artifacts (white artifact: p<0.005, angle of the streak artifact: p<0.0001, number of the streak artifact: p<0.0001).
Conclusions Metallic artifact was increased when the degree of angle between the clip blade and z axis became near to zero. Clip artifacts after aneurysmal clipping could be minimized with simple maneuvers such as minimal changes of the scan gantry angle on the lateral scout view if the clip blade was parallel to the gantry angle or the clip spring portion was included in the scan cross section.
- © 2012 by American Heart Association, Inc.