A methodology for in silico endovascular repair of abdominal aortic aneurysms

Abstract

Endovascular aneurysm repair (EVAR) can involve some unfavorable complications such as endoleaks or stent-graft (SG) migration. Such complications, resulting from the complex mechanical interaction of vascular tissue, SG and blood flow or incompatibility of SG design and vessel geometry, are difficult to predict. Computational vascular mechanics models can be a predictive tool for the selection, sizing and placement process of SGs depending on the patient-specific vessel geometry and hence reduce the risk of potential complications after EVAR. In this contribution, we present a new in silico EVAR methodology to predict the final state of the deployed SG after intervention and evaluate the mechanical state of vessel and SG, such as contact forces and wall stresses. A novel method to account for residual strains and stresses in SGs, resulting from the precompression of stents during the assembly process of SGs, is presented. We suggest a parameter continuation approach to model various different sizes of SGs within one in silico EVAR simulation which can be a valuable tool when investigating the issue of SG oversizing. The applicability and robustness of the proposed methods are demonstrated on the example of a synthetic abdominal aortic aneurysm geometry.

In silico study of vessel and stent‐graft parameters on the potential success of endovascular aneurysm repair

“…While positive effects of stent predeformation ω on the radial buckling of the graft and the SG fixation were reported for instance in Hemmler et al, in Figure C, we explicitly show some downsides of stent predeformation. Larger degrees of stent predeformation ω result in higher vessel overstresses .…”

Patient-specific in silico endovascular repair of abdominal aortic aneurysms: application and validation

“…The objective of this work is the application of the in silico EVAR methodology that was recently published by our group [28] to patient-specific cases with bifurcated, marketed SGs. This involves the development of a continuous process chain which includes the following steps: (1) medical imaging of preinterventional CT data, (2) automated model generation of patientspecific vessels and SGs, (3) application of the in silico EVAR methodology as well as (4) postprocessing and mechanical interpretation of simulation results.…”

“…In this study, the in silico EVAR methodology based on finite element methods (FEM) that was proposed in [28] is applied to three patient-specific cases treated by Cook Zenith Flex R and Cook Zenith Spiral-Z R SGs. Model and model parameter uncertainties inherent to patient-specific modeling as well as the variety of vessel geometries and complex shapes of marketed SGs are further challenges compared to the application of the in silico EVAR methodology to synthetic AAAs in [28]. The in silico EVAR methodology aims at finding the final deployed SG configuration in the vessel geometry rather than reproducing the intrainterventional steps of EVAR.…”

“…The methodology considers in vivo non-stressfree vessel geometries extracted from in vivo CT images by the prestressing methodology proposed in [23]. A stent predeformation methodology [28] is applied to account for residual strains and stresses that exist in most marketed SGs. Attention is payed to detailed modeling of all vessel and aneurysm constituents as they can have a distinct impact on the outcome of EVAR [68,58,67].…”

“…Several studies have already been conducted in the field of in silico EVAR approaches in idealized vessel geometries (e.g. [51,14,15,48,28]). Some studies have been published on the virtual deployment of stents in patient-specific vessels (e.g.…”