Semi-automatic aortic endograft localisation for post-operative evaluation of endovascular aneurysm treatment

Abstract

A semi-automatic method for localisation and segmentation of bifurcated aortic endografts in CTA images is presented. The graft position is established through detection of radiopaque markers sewn on the outside of the graft. The user indicates the first and the last marker, whereupon the rest of the markers are detected automatically by second order scaled derivative analysis combined with prior knowledge of graft shape and marker configuration. The marker centres obtained approximate the graft sides and central axis. The graft boundary is determined, either in the original CT slices or in reformatted slices orthogonal to the local graft axis, by maximizing the local gradient in the radial direction along a deformable contour passing through both sides. The method has been applied to ten CTA images. In all cases, an adequate segmentation is obtained. Compared to manual segmentations an average similarity (i.e. relative volume of overlap) of 0.93 ± 0.02 for the graft body and 0.84 ± 0.05 for the limbs is found