Evaluation of Clip Artefacts in Three-dimensional Computed Tomography

Objective: Recently, three-dimensional CT angiography (3D-CTA) has been used as a diagnostic method in postoperative evaluation after aneurysm clipping. A systematic analysis of possible predictors for good image quality needs to be conducted if 3D-CTA is to replace digital subtraction angiography in the postoperative setting. The aim of this study was to evaluate the influence of clip orientation on image quality and to assess titanium clip artefacts quantitatively on 3D-CTA. Material and Method: Four different Yasargil titanium clips were placed on an acrylic glass tablet. Standardised 3D-CTA scanning was performed at clip-gantry angles of 0, 45 and 90. Multiplanar reconstructions of the clips in frontal and lateral projections were performed. 3D-CTA image quality and the severity of titanium artefacts were judged by four observers. Results: Twenty-four images were evaluated. Using frontal reconstructions, clip artefacts at a clip-gantry angle of 0 were almost exclusively distributed along the long axis of the clip, with excellent evaluation quality at the lateral side of the clip branches. With decreasing clip-gantry angle (90 and 45) strong artefacts were localised laterally. On lateral reconstructions image quality was not significantly more restricted, regardless of the clip-gantry angles used. Conclusion: 3D-CTA image quality can be severely limited by clip artefacts. The expression and distribution of these artefacts depends on both the clip-gantry angle and the plane of image reconstruction. Overall, there is no correlation between clip-gantry angle and either the severity or the spatial distribution of clip artefacts leading to observable restrictions in the evaluation of surrounding structures.