Haemodynamic imaging of thoracic stent-grafts by computational fluid dynamics (CFD): presentation of a patient-specific method combining magnetic resonance imaging and numerical simulations
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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.
• 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.
KeywordsTime-resolved 3D MRI CFD TEVAR Stent-graft Haemodynamics
Magnetic resonance imaging
Computational fluid dynamics
Thoracic endovascular aortic repair
Magnetic resonance angiography
Phase contrast imaging
Wall shear stress
Balanced turbo field echo
Thoracic aortic aneurysms
Acute traumatic aortic rupture
Ramiro Moreno has been financed during the development of the project by the Medtronic Vascular (Santa Rosa, CA); the project OCFIA has been supported by the French National Agency for Research (ANR 07-CIS7-006-01). CINES (Montpellier) is acknowledged for CFD calculations.
The early results of the project have been presented twice at the ECR, in 2008 and in 2011. The first presentation was honoured with the first prize in the vascular topic, of which we are sincerely proud.
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