Patient-specific simulation of endovascular repair surgery with tortuous aneurysms requiring flexible stent-grafts

Abstract

The rate of post-operative complications is the main drawback of endovascular repair, a technique used to treat abdominal aortic aneurysms. Complex anatomies, featuring short aortic necks and high vessel tortuosity for instance, have been proved likely prone to these complications. In this context, practitioners could benefit, at the preoperative planning stage, from a tool able to predict the post-operative position of the stent-graft, to validate their stent-graft sizing and anticipate potential complications. In consequence, the aim of this work is to prove the ability of a numerical simulation methodology to reproduce accurately the shapes of stent-grafts, with a challenging design, deployed inside tortuous aortic aneurysms. Stent-graft module samples were scanned by X-ray microtomography and subjected to mechanical tests to generate finite-element models. Two EVAR clinical cases were numerically reproduced by simulating stent-graft models deployment inside the tortuous arterial model generated from patient pre-operative scan. In the same manner, an in vitro stent-graft deployment in a rigid polymer phantom, generated by extracting the arterial geometry from the preoperative scan of a patient, was simulated to assess the influence of biomechanical environment unknowns in the in vivo case. Results were validated by comparing stent positions on simulations and post-operative scans. In all cases, simulation predicted stents deployed locations and shapes with an accuracy of a few millimetres. The good results obtained in the in vitro case validated the ability of the methodology to simulate stent-graft deployment in very tortuous arteries and led to think proper modelling of biomechanical environment could reduce the few local discrepancies found in the in vivo case. In conclusion, this study proved that our methodology can achieve accurate simulation of stent-graft deployed shape even in tortuous patient specific aortic aneurysms and may be potentially helpful to help practitioners plan their intervention.

Predictive Numerical Simulations of Double Branch Stent-Graft Deployment in an Aortic Arch Aneurysm

“…Future work could refine the action of blood pressure. However, given the level of complexity of our simulations and the very good agreement with post-operative CT scans, quasi-static FEA proved to be a reasonable and reliable first approximation for aortic arch aneurysm, as previously demonstrated in iliac arteries, ascending thoracic aortas and abdominal aortic aneurysms 3,10,11,[32][33][34] . Complementary studies with computational fluid dynamic could help understanding the drag forces acting on the SG and explain further some of the deviations reported in this study 39 .…”

“…Simulation assessment Positions of stent rings obtained from the post-operative CT scan were chosen as reference positions to validate our deployment simulation. A similar assessment method was used in previous studies 32,33 . Stent rings were manually segmented from CT scans using MevisLab ® .…”

“…The morphing algorithm 32,33 was fully adapted to the aortic arch anatomy. This required accounting for the high degree of curvature and incorporation of the supra-aortic trunk vessels.…”

Model reduction methodology for computational simulations of endovascular repair

“…For SG-S, the graft was modeled as an orthotropic linear elastic material and meshed with linear 4-node shell elements (S4R), see table 1. Additionally, and considering that the superelastic behavior of Nitinol remained in its austenitic phase during SG deployment, and according to measured austenitic modulus, the Nitinol stent was modeled as a linear elastic material [19]. The stent was meshed with linear beam elements (B31), see table 1.…”

3D printed abdominal aortic aneurysm phantom for image guided surgical planning with a patient specific fenestrated endovascular graft system

“…Use of these phantoms to practice various approaches has shown promise as a method to improve clinical interventional training and reduce the risk of periprocedural complications. Patient specific AAA phantoms fabricated via additive manufacturing have been used to visualize complex anatomies and create models for mock graft deployment [11–14] . Previous investigations have traditionally been fabricated from stiff photopolymers that lack compliance of arteries vital for graft deployment.…”