  In this paper we present an efficient algorithm for the segmentation of the
inner and outer boundary of thoratic and abdominal aortic aneurysms (TAA & AAA)
in computed tomography angiography (CTA) acquisitions. The aneurysm
segmentation includes two steps: first, the inner boundary is segmented based
on a grey level model with two thresholds; then, an adapted active contour
model approach is applied to the more complicated outer boundary segmentation,
with its initialization based on the available inner boundary segmentation. An
opacity image, which aims at enhancing important features while reducing
spurious structures, is calculated from the CTA images and employed to guide
the deformation of the model. In addition, the active contour model is extended
by a constraint force that prevents intersections of the inner and outer
boundary and keeps the outer boundary at a distance, given by the thrombus
thickness, to the inner boundary. Based upon the segmentation results, we can
measure the aneurysm size at each centerline point on the centerline orthogonal
multiplanar reformatting (MPR) plane. Furthermore, a 3D TAA or AAA model is
reconstructed from the set of segmented contours, and the presence of endoleaks
is detected and highlighted. The implemented method has been evaluated on nine
clinical CTA data sets with variations in anatomy and location of the pathology
and has shown promising results.
