Quantification of the migration and deformation of abdominal aortic aneurysm stent grafts
2006
The endovascular repair of an abdominal aortic aneurysm is a minimal
invasive therapy which has been established during the past 15 years. A stent-graft is placed inside the aorta in order to cover the weakened regions of its wall. During a time interval of one or
more years the stent-graft can migrate and deform with the risk of
the occlusion of one of its limbs or of the rupture of the aneurysm.
In this work we developed several strategies to quantify the
migration and deformation in order to assess the risk coming with
these movements and especially to characterize appearing
complications by them. We calculated the rigid movement of the
stent-graft and the aorta relative to the spinal canal. For this
purpose, firstly, we rigidly registered the spinal canals, extracted
for the different points in time, in order to establish a fixed
reference system. All objects have been segmented first and surface
points have been determined before applying a rigid and non-rigid
point set registration algorithm. The change in the residual error
after registration of the stent-graft with an increasing number
of degrees of freedom indicates the amount of change in the
stent-graft's morphology. We investigated a sample of 9. Two cases could be clearly
distinguished by the quantified parameters: a high global migration
and a strong reduction of the residual error after non-rigid
registration. In both cases, strong complications have been
detected by the examination of clinical experts but only by means of the
images acquired one year later.
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