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ABSTRACT: PURPOSE: Although the widespread acceptance of thoracic endovascular aortic repair (TEVAR) as a first-line treatment option for a multitude of thoracic aortic diseases, little is known about the consequences of the device implantation on the native aortic anatomy. We propose a comparative analysis of the pre- and postoperative geometry on a clinical series of patients and discuss the potential clinical implications METHODS: CT pre- and postoperative acquisitions of 30 consecutive patients treated by TEVAR for different pathologies (20 thoracic aortic aneurysms, 6 false aneurysms, 3 penetrating ulcers, 1 traumatic rupture) were used to model the vascular geometry. Pre- and postoperative geometries were compared for each patient by pairing and matching the 3D models. An implantation site was identified, and focal differences were detected and described. RESULTS: Segmentation of the data sets was successfully performed for all 30 subjects. Geometry differences between the pre- and postoperative meshes were depicted in 23 patients (76 %). Modifications at the upper implantation site were detected in 14 patients (47 %), and among them, the implantation site involved the arch (Z0-3) in 11 (78 %). CONCLUSION: Modeling the vascular geometry on the basis of imaging data offers an effective tool to perform patient-specific analysis of the vascular geometry before and after the treatment. Future studies will evaluate the consequences of these changes on the aortic function.
CardioVascular and Interventional Radiology 03/2013; · 2.09 Impact Factor
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ABSTRACT: In the last decade, there was been increasing interest in finding imaging techniques able to provide a functional vascular imaging of the thoracic aorta. The purpose of this paper is to present an imaging method combining magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) to obtain a patient-specific haemodynamic analysis of patients treated by thoracic endovascular aortic repair (TEVAR).
MRI was used to obtain boundary conditions. MR angiography (MRA) was followed by cardiac-gated cine sequences which covered the whole thoracic aorta. Phase contrast imaging provided the inlet and outlet profiles. A CFD mesh generator was used to model the arterial morphology, and wall movements were imposed according to the cine imaging. CFD runs were processed using the finite volume (FV) method assuming blood as a homogeneous Newtonian fluid.
Twenty patients (14 men; mean age 62.2 years) with different aortic lesions were evaluated. Four-dimensional mapping of velocity and wall shear stress were obtained, depicting different patterns of flow (laminar, turbulent, stenosis-like) and local alterations of parietal stress in-stent and along the native aorta.
A computational method using a combined approach with MRI appears feasible and seems promising to provide detailed functional analysis of thoracic aorta after stent-graft implantation. KEY POINTS : • Functional vascular imaging of the thoracic aorta offers new diagnostic opportunities • CFD can model vascular haemodynamics for clinical aortic problems • Combining CFD with MRI offers patient specific method of aortic analysis • Haemodynamic analysis of stent-grafts could improve clinical management and follow-up.
European Radiology 05/2012; 22(10):2094-102. · 3.22 Impact Factor
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High Performance Computing for Computational Science - VECPAR 2008, 8th International Conference, Toulouse, France, June 24-27, 2008. Revised Selected Papers; 01/2008
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ABSTRACT: Hemodynamic factor in the thoracic aorta is believed to play an important role in the initiation and the progress of endovascular injuries. Most reported studies are dealing with averaged physiological geometries and rigid arterial boundaries. However, for diseases such as the aortic dissection, the geometrical changes are very patient-specific and the wall motions over the cardiac cycle influence the blood flow drastically. There is a need to generalize the patient-specific studies where the actual inlet/outlet boundary conditions and wall motions are accounted for. But in the most general approach, the geometrical changes during the cardiac cycle result from the coupled fluid-structure interaction problem. This path is very challenging because the density of blood and tissues are of the same order, the rheology of the vessels is far from well understood and because the actual answer depends on the interaction of the arteries with the surrounding organs. Another option is to study the respond of the blood flow submitted to prescribed wall motions and geometry changes. Our study propose a method to build patient-specific geometric data and boundary conditions for unsteady CFD runs with variable meshes valid over the cardiac cycle. We develop a specific MRI protocol in order to extract the full geometric data at several phases over the cardiac cycle. Hemodynamic boundary conditions (velocity inlet and pressure outlets) were acquired by means of anothers two sequences into the same MRI device, a velocity-encoded MR imaging 1 for the velocity inlet profile and a pressure-gradients-encoded imaging 2 for the outlets. Static vascular surfaces have been extracted by means of Level Set methods 3 , after developing a noise reduction strategy called 'selective blurring filter' 4 . Finally, the mesh movement has been imposed to the static mesh according to dynamic MRI sequence by means of a non linear transformation field, computed from dynamic vascular images by means of bayesian algorithm 5 . The proposed approach permits the computation of the blood flow under realistic in vivo, time evolving conditions. It is much simpler than the full coupled fluid-structure problem and has the potential to provide a better picture of the specific hemodynamic status. Insights about the physiopathology of some arterial disease are also expected.
01/2006;
