Scanner Somatom Definition à double énergie : application à la caractérisation lésionnelle des plaques vulnérables d'athérosclérose et à l'analyse fonctionnelle du ventricule gauche

Les complications de l'athérosclérose sont responsables des deux premières causes de mortalité dans le monde. Ces deux causes représentent à elles seules plus de 20 % des décès à l'échelle mondiale. Elles concernent en France et dans le monde, en particulier les pays industrialisés, une population sans cesse croissante. Le scanner est l'une des modalités d'imagerie qui permet le diagnostic de cette pathologie cardiaque, cependant son utilisation se limite aujourd'hui à la détection de sténoses oblitérant significativement la lumière du vaisseau. Au cours de ce travail de thèse, l'objectif a été d'exploiter les potentialités du scanner double énergie développé par Siemens Healthcare pour, d'une part, une meilleure caractérisation de la plaque lipidique d'athérosclérose grâce au développement d'un programme de traitement d'image en postreconstruction, et d'autre part, la mise en application d'un code de déformation numérique développé au laboratoire permettant l'analyse du retentissement biomécanique de la plaque d'athérosclérose à travers l'obtention de différents paramètres, à la fois globaux et régionaux, de la fonction ventriculaire gauche (paramètres globaux : fraction d'éjection globale, index de sphéricité ; paramètres régionaux : strain lagrangien, vitesse de strain, déplacement naturel, fraction d'éjection segmentaire). L'objectif final est de mettre à la disposition du clinicien un outil de diagnostic complémentaire aux techniques actuelles.Complications of atherosclerosis are responsible for the two leading causes of death worldwide. These two causes alone account for more than 20% of deaths worldwide. They concern in France and around the world, in particular the industrialized countries, a growing population. The scanner is an imaging modalities allowing the diagnosis of cardiac disease, however its use is now limited to the detection of stenosis significantly obliterating the vessel lumen. In this thesis, the objective was to , on the one hand, exploit the potential of dual energy scanner developed by Siemens Healthcare for a better characterization of the atherosclerotic plaque by developing an image processing program in postreconstruction, and on the other hand, the implementation of a numerical deformation code developed in the laboratory for analysis of the biomechanical impact of atherosclerotic plaque through obtaining various parameters of left ventricular function both global and regional (global parameters: global ejection fraction, sphericity index; regional parameters : lagrangian strain, strain rate, natural movement, segmental ejection fraction). Finally, the main goal is to make available to the clinician a diagnostic tool complementary to current techniques

Scanner Somatom Definition à double énergie (application à la caractérisation lésionnelle des plaques vulnérables d'athérosclérose et à l'analyse fonctionnelle du ventricule gauche)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Haemodynamic imaging of thoracic stent-grafts by computational fluid dynamics (CFD): presentation of a patient-specific method combining magnetic resonance imaging and numerical simulations

International audienceOBJECTIVES: 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). METHODS: 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. RESULTS: 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. CONCLUSIONS: 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