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PhD position offered at SAINBIOSE – INSERM U1059 – Mines Saint-Etienne
Computational simulation of post-interventional complications following endovascular aneurysm repair
Keywords: Fluid mechanics, modelling, mechanobiology, aneurysm, Endovascular Aneurysm Repair
Academic context: This PhD position is part of a large interdisciplinary project funded by the RHU program in France and named EndovX, aiming to develop novel technologies for personalized medicine in aortic disease. The group in Sainbiose Mines Saint-Etienne contributes to the project through the development of computational models ensuring accurate predictions of post-interventional conditions at an affordable computational cost. The group has a strong expertise in the domain of soft tissue and fluid biomechanics for the cardiovascular system, especially focused on aortic aneurysms.
Scientific context: EndoVascular Aneurysm Repair (EVAR) is a minimally invasive interventional procedure for the treatment of abdominal aortic aneurysms. One or multiple stent grafts, specifically tailored to the patient’s anatomy, are deployed into the descending and abdominal aorta and, in the case of fenestrated EVAR (named FEVAR), into the aortic branches (renal arteries, mesenteric artery and celiac trunk). These devices redirect the blood flow into a reconstructed lumen, isolating the aortic wall from the blood pressure and, hence, preventing the risk of rupture of the aneurysm. However, reintervention rates due to post-surgical complications still stagnate at 2 to 5% despite the continuous improvement of (F)EVAR technologies. A significant fraction of complications is related to altered hemodynamics conditions following an EVAR intervention, which can lead for instance to the occlusion of a branch or of a distal artery, subsequent to intimal hyperplasia and/or thrombosis. This PhD thesis aims to predict computationally the alteration of blood flows induced by the deployment of a stent graft in FEVAR interventions and to assess quantitative descriptors of altered hemodynamics that can be related to these complications.
Project summary: Our group has previously developed a numerical framework based on the CRIMSON software to simulate the post-EVAR hemodynamics in the descending aorta and a numerical framework based on the ABAQUS software to predict the position of stent grafts after deployment. Building on this work, this thesis will focus on merging these frameworks for patients who underwent FEVAR. In vivo hemodynamics measurements before and after FEVAR will be obtained through a clinical study. Segmentation of pre-FEVAR 3D images of the descending aorta and abdominal arterial branches will be used to reconstruct patient-specific models. The post-FEVAR geometry will be computed using the finite-element method and fluid dynamics equations will be solved in the obtained post-FEVAR geometry to simulate the post-FEVAR blood flows. Special focus will be given to the renal arteries, to characterize how the stresses applied onto the arterial walls and how the hemodynamics conditions are modified by the intervention. The results will be compared against follow-up medical imaging, to better understand how this modified hemodynamics can lead to a complication like intimal hyperplasia or an occlusion. Using 3D images of patients who developed such complications, simulations will be implemented again to understand the feedback between the resulting complication and the post-treatment hemodynamics, and how this unstable mechanism can potentially lead to thrombosis.
The work involves the combination of medical image processing and fluid and structure numerical simulations. It will run in close collaboration with cardiovascular surgeons of the EndovX project and with the Multiphase and Cardiovascular Lab at the University of Washington, Seattle, USA.
Student profile: Background in fluid mechanics. Previous training in CFD and/or finite element analysis and good knowledge of continuum mechanics will be appreciated. Curiosity for biomedical applications. Interest in mechanobiology.
Administrative aspects: The employer is Mines Saint-Etienne, a school of Institut Mines Telecom. This PhD is funded for 36 months, starting 1st October 2022 and includes a stay at the University Washington in Seattle, USA, to work with Pr. Alberto Aliseda. The PhD will be under the supervision of Prof Stéphane Avril and Dr Fanette Chassagne (Mines Saint-Etienne).
If you are interested, send a curriculum vitae, a cover letter describing previous research experience and interests, the names and contact information of two references. Please, submit via email with “EVAR PhD” on the subject line to Prof Stéphane AVRIL, PhD (avril@emse.fr) and Fanette Chassagne, PhD (fanette.chassagne@emse.fr).
Computational simulation of post-interventional complications following endovascular aneurysm repair
Keywords: Fluid mechanics, modelling, mechanobiology, aneurysm, Endovascular Aneurysm Repair
Academic context: This PhD position is part of a large interdisciplinary project funded by the RHU program in France and named EndovX, aiming to develop novel technologies for personalized medicine in aortic disease. The group in Sainbiose Mines Saint-Etienne contributes to the project through the development of computational models ensuring accurate predictions of post-interventional conditions at an affordable computational cost. The group has a strong expertise in the domain of soft tissue and fluid biomechanics for the cardiovascular system, especially focused on aortic aneurysms.
Scientific context: EndoVascular Aneurysm Repair (EVAR) is a minimally invasive interventional procedure for the treatment of abdominal aortic aneurysms. One or multiple stent grafts, specifically tailored to the patient’s anatomy, are deployed into the descending and abdominal aorta and, in the case of fenestrated EVAR (named FEVAR), into the aortic branches (renal arteries, mesenteric artery and celiac trunk). These devices redirect the blood flow into a reconstructed lumen, isolating the aortic wall from the blood pressure and, hence, preventing the risk of rupture of the aneurysm. However, reintervention rates due to post-surgical complications still stagnate at 2 to 5% despite the continuous improvement of (F)EVAR technologies. A significant fraction of complications is related to altered hemodynamics conditions following an EVAR intervention, which can lead for instance to the occlusion of a branch or of a distal artery, subsequent to intimal hyperplasia and/or thrombosis. This PhD thesis aims to predict computationally the alteration of blood flows induced by the deployment of a stent graft in FEVAR interventions and to assess quantitative descriptors of altered hemodynamics that can be related to these complications.
Project summary: Our group has previously developed a numerical framework based on the CRIMSON software to simulate the post-EVAR hemodynamics in the descending aorta and a numerical framework based on the ABAQUS software to predict the position of stent grafts after deployment. Building on this work, this thesis will focus on merging these frameworks for patients who underwent FEVAR. In vivo hemodynamics measurements before and after FEVAR will be obtained through a clinical study. Segmentation of pre-FEVAR 3D images of the descending aorta and abdominal arterial branches will be used to reconstruct patient-specific models. The post-FEVAR geometry will be computed using the finite-element method and fluid dynamics equations will be solved in the obtained post-FEVAR geometry to simulate the post-FEVAR blood flows. Special focus will be given to the renal arteries, to characterize how the stresses applied onto the arterial walls and how the hemodynamics conditions are modified by the intervention. The results will be compared against follow-up medical imaging, to better understand how this modified hemodynamics can lead to a complication like intimal hyperplasia or an occlusion. Using 3D images of patients who developed such complications, simulations will be implemented again to understand the feedback between the resulting complication and the post-treatment hemodynamics, and how this unstable mechanism can potentially lead to thrombosis.
The work involves the combination of medical image processing and fluid and structure numerical simulations. It will run in close collaboration with cardiovascular surgeons of the EndovX project and with the Multiphase and Cardiovascular Lab at the University of Washington, Seattle, USA.
Student profile: Background in fluid mechanics. Previous training in CFD and/or finite element analysis and good knowledge of continuum mechanics will be appreciated. Curiosity for biomedical applications. Interest in mechanobiology.
Administrative aspects: The employer is Mines Saint-Etienne, a school of Institut Mines Telecom. This PhD is funded for 36 months, starting 1st October 2022 and includes a stay at the University Washington in Seattle, USA, to work with Pr. Alberto Aliseda. The PhD will be under the supervision of Prof Stéphane Avril and Dr Fanette Chassagne (Mines Saint-Etienne).
If you are interested, send a curriculum vitae, a cover letter describing previous research experience and interests, the names and contact information of two references. Please, submit via email with “EVAR PhD” on the subject line to Prof Stéphane AVRIL, PhD (avril@emse.fr) and Fanette Chassagne, PhD (fanette.chassagne@emse.fr).