Dissertationen zum Thema „Simulations hémodynamiques“
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Garreau, Morgane. „Simulations hémodynamiques pour l'IRM : contrôle qualité, optimisation et intégration à la pratique clinique“. Electronic Thesis or Diss., Université de Montpellier (2022-....), 2023. http://www.theses.fr/2023UMONS040.
Der volle Inhalt der QuelleThe study of hemodynamics, i.e. the dynamics of blood flow, is considered by the medical community as an essential biomarker to characterize the onset and the development of cardiovascular pathologies. Historically, magnetic resonance imaging (MRI), a non-invasive and non-ionizing technique, allows to reconstruct morphological images of the biological tissues. Recent progresses have made it possible to access the temporal evolution of the blood velocity field in the three spatial directions. This technique, known as 4D flow MRI, is still little used in the clinical practice due to its low spatiotemporal resolution and its long scan time.This thesis aims at studying how the 4D flow MRI sequence performs. To begin with, the impact of accelerated sequences (GRAPPA, compressed sensing) on reconstructed velocity fields is studied in a framework combining experimental measurements in a flow phantom and computational fluid dynamics (CFD) simulations. It is shown that the highly accelerated sequence with compressed sensing is in good agreement with numerical simulation as long as appropriate corrections are applied, namely with respect to the eddy currents. Then, the impact of a sequence parameter, namely partial echo, is investigated. The study is conducted thanks to a methodology coupling the simulation of the MR acquisition process with CFD and allowing to reconstruct synthetic MR images (SMRI). This configuration is freed from experimental errors and allows to only focus on the errors intrinsic to the MRI process. Two realistic constructor sequences, without and with partial echo, are simulated for two types of flow in a numerical flow fantom. For both flows, the sequence with partial echo results in overall better results. It suggests that the mitigation of the displacement artifacts made possible by the partial echo has a greater impact than the reduced MR signal acquired that it induces. Furthermore, the coupled MRI-CFD simulation appears as a tool of interest in the context of sequence design and optimization. It could be expanded to other types of MR sequences
Saccaro, Ludovica. „Vers l'évaluation du risque des anévrismes de l'aorte abdominale par modélisation géométrique et simulations hémodynamiques d'ordre réduit“. Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0025.
Der volle Inhalt der QuelleThis thesis focuses on a specific pathology affecting the abdominal section of the aorta, known as abdominal aortic aneurysm (AAA). An aneurysm involves a persistent and localized weakening of the vessel wall, leading to enlargements and bulges, causing recirculation and turbulence of blood flow.Our thesis outlines a methodology for geometric modeling of abdominal aneurysms. The process involves acquiring CT images, reconstructing the aorta 3D geometry, and isolating the aneurysm. The modeling phase begins by identifying and approximating the centerline of the aortic vessel using B-spline functions. The aortic wall is then partitioned and profiled using Fourier series.To evaluate its effectiveness, the developed technique is applied to a dataset of CT scans from patients. Reconstructions obtained from the scans are also presented as examples to detail each step of the procedure. In addition, a quantitative evaluation and rationale behind modeling parameters are explained. Then, as a first application, the modeling is integrated into a registration process for clinical diagnosis and follow-up.The geometrical modeling procedure developed is used in a pipeline for hemodynamic simulations and risk assessment, employing a reduced-order modeling approach to construct a reduced solution space. Simulations, utilizing parameterized geometries, are conducted under realistic conditions, and risk indicators are computed and linked to the geometrical representation using Radial Basis Functions interpolant. Finally, predictions on risk indicators are obtained for an unknown geometry. The results, despite being promising, can be further improved by appropriately augmenting the initial dataset.To address the aforementioned scarcity of clinical data, we devised an automated workflow for generating synthetic geometries. This approach allows for the identification of relevant geometry parameters and involves machine learning to generate a virtual patient population consistent with the original data. In addition to improving the predictive capability of reduced models, the method can also be applied prospectively for in-silico trials and studies involving virtual patient populations
Bollache, Emilie. „Caractérisation hémodynamique de l'aorte thoracique par IRM, tonométrie d'applanation et simulations numériques“. Phd thesis, Université Pierre et Marie Curie - Paris VI, 2014. http://tel.archives-ouvertes.fr/tel-00958757.
Der volle Inhalt der QuelleBossuet, Philippe. „Simulation in vitro de la macrocirculation cérébrale en pathologie carotidienne : comparaison aux données de la simulation numérique“. Toulouse, INPT, 1997. http://www.theses.fr/1997INPT060H.
Der volle Inhalt der QuelleEvin, Morgane. „Caractérisation de la fonction hémodynamique suite au remplacement valvulaire mitral. Etude in-vitro“. Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4123.
Der volle Inhalt der QuelleThis PhD work is divided into four different parts. the first part concerns the hemodynamic characterization by in-vitro cardiovascular testing of mitral valvular prosthesis from different manufacturers in order to provide reference values for clinical diagnosis. The second part focus on bi leaflet mechanical heart valve in each pressure recovery resulting of flow through the three orifices could lead to an overestimation of transvalvular pressure gradient. This could create ambigious assessment in case of high value of transvalvular pressure gradient. This part aims to quantify this pressure recovery and identify the influence of dysfunction (leaflet obstruction or patient prosthesis mismatch) on this value. Third part consists in valve-in-valve procedure in which a transcatheter valve is impllanted in a failled bioprosthesis. It provides in vitro testing, first globally, of assemblies composed of SAPIEN Edwards prostheses in different manufacturers' bioprosthesis.As highlighted in the previous parts inflows of the mitral prostheses can not be considered as plane and results of left atrium flow patterns. The last part studies the left atrium flow following mitral valve replacement
Levilly, Sébastien. „Quantification de biomarqueurs hémodynamiques en imagerie cardiovasculaire par résonance magnétique de flux 4D“. Thesis, Ecole centrale de Nantes, 2020. http://www.theses.fr/2020ECDN0007.
Der volle Inhalt der QuelleIn cardiovascular imaging, a biomarker is quantitative information correlated with an existing or growing cardiovascular pathology. Biomarkers are generally obtained by anatomy and blood flow imaging. Recently, the 4D Flow MRI sequence opened new opportunities in measuring the blood flow within a 3D volume along the cardiac cycle. However, this sequence is a compromise between signalto-noise ratio, resolution and acquisition time. Allocated time being limited, velocity measurements are noisy and low resolution. In that context, biomarkers' quantification is challenging. This thesis's purpose is to enhance biomarkers' quantification and particularly for the wall shear stress (WSS). Two strategies have been investigated to reach that objective. A first solution allowing the spatiotemporal filtering of the velocity field has been proposed. It revealed the importance of the wall for the velocity field modelization. A second approach, being the major contribution of this work, focused on the design of a WSS quantification algorithm. This algorithm, named PaLMA, is based on the local modelization of the wall to build a velocity model near a point of interest. The WSS is computed from the velocity model. This algorithm embeds an a posteriori regularization step to improve the WSS quantification. Besides, a blurring model of 4D Flow MRI is used for the first time in the WSS quantification context. Finally, this algorithm has been validated over synthetic datasets, with carotids' complex flows, concerning the signal-to-noise ratio, the resolution, and the segmentation. The performances of PaLMA are superior to a reference solution in that domain, within a clinical routine context
Tanné, David. „Déterminants hémodynamiques de l'hypertension pulmonaire et de la thromboembolie suite au remplacement valvulaire mitral : étude in-vitro sur un simulateur atrio-ventriculaire gauche et pulmonaire“. Thesis, Université Laval, 2009. http://www.theses.ulaval.ca/2009/26014/26014.pdf.
Der volle Inhalt der QuelleMitral valve diseases induce left atrial pressure or volume overload. The resulting increase of left atrial pressure, in turn, leads to secondary abnormalities, such as pulmonary arterial hypertension, atrial fibrillation and thromboembolism. Therefore, the main goals of mitral valve replacement are to restore the valvular hemodynamics and to normalize the secondary abnormalities. The general objective of this thesis is to better understand the complex interactions between the valve substitute, the intra-atrial flow patterns, and the pulmonary circulation. We, therefore, developed a new in-vitro pulsed atrio-ventricular mock circulatory system to investigate these interactions. The setup is based on the perfect synchronization between the contractions and relaxations of the two cardiac cavities, which are mimicked by two silicone moulds. Two pumps, real time servo-controlled, allow the double rigid and synchronized activations of the moulds, and the control of left atrial and left ventricular volumes. A Windkessel model is used as the pulmonary circulation and a third pump mimick the right ventricular ejection. Pressure-volume curves of the cardiac cavities and aortic and pulmonary impedances, measured in-vitro, are totally concordant with the cardiac physiology, except the amplitude of the left atrial pressure which remains too elevated. The anatomical shape of the left atrial mould includes the four pulmonary veins and the left atrial appendage. This realistic geometry allows flow patterns very closed to those observed in-vivo. Their visualization is performed using multi-planes three components particle image velocimetry, associated with an automatic mask generation. Using a numerical approach, we investigated the impact of mitral prosthesis-patient mismatch on left atrial and pulmonary arterial pressures. The numerical model was used to validate the cut-off values of indexed effective orifice areas generally used to define the presence and the severity of prosthesis-patient mismatch in the clinical setting. With the use of the mock circulatory system, we showed that the effective orifice area of mitral prostheses may exhibit variations of ±30% during diastole, which contradicts the previous hypothesis stating that this variable remains constant during this period. Finally, we described the positive impact of the mechanical mitral prosthetic valve regurgitation on thrombogenesis, similarly to mitral insufficiency, to the expense of an increase of the pulmonary arterial pressure. The new knowledge and the new experimental setup presented in this thesis may prove to be useful to optimize the design of mitral prosthetic valves and the performance of mitral valve replacement.
Aletti, Matteo Carlo Maria. „Mathematical modelling and simulations of the hemodynamics in the eye“. Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066031/document.
Der volle Inhalt der QuelleThe structure of the eye offers a unique opportunity to directly observe the microcirculation, by means, for instance, of fundus camera, which are cheap devices commonly used in the clinical practice. This can facilitate the screening of systemic deseases such as diabetes and hypertension, or eye diseases such as glaucoma. A key phenomenon in the microcirculation is the autoregulation, which is the ability of certain vessels to adapt their diameter to regulate the blood flow rate in response to changes in the systemic pressure or metabolic needs. Impairments in autoregulation are strongly correlated with pathological states. The hemodynamics in the eye is influenced by the intraocular pressure (IOP), the pressure inside the eye globe, which is in turn influenced by the ocular blood flow. The interest in the IOP stems from the fact that it plays a role in several eye-diseases, such as glaucoma. Mathematical modelling can help in interpreting the interplay between these phenomena and better exploit the available data. In the first part of the thesis we present a simplified fluid-structure interaction model that includes autoregulation. A layer of fibers in the vessel wall models the smooth muscle cells that regulate the diameter of the vessel. The model is applied to a 3D image-based network of retinal arterioles. In the second part, we propose a multi-compartments model of the eye. We use the equations of poroelasticity to model the blood flow in the choroid. The model includes other compartments that transmit the pulsatility from the choroid to the anterior chamber, where the measurements of the IOP are actually performed. We present some preliminary results on the choroid, the aqueous humor and on the choroid coupled with the vitreous. Finally, we present a reduced order modelling technique to speed up multiphysics simulations. We use high fidelity models for the compartments of particular interest from the modelling point of view. The other compartments are instead replaced by a reduced representation of the corresponding Steklov-Poincaré operator
Puiseux, Thomas. „Numerical simulations for phase-contrast magnetic resonance imaging“. Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS109.
Der volle Inhalt der QuelleHemodynamics (blood flow dynamics) is now recognized as a key marker in the onset and evolution of many cardiovascular disorders such as aneurysms, stenoses, or blood clot formation. As it provides a comprehensive access to blood flows in-vivo, time-resolved 3D phase-contrast magnetic resonance imaging (or 4D Flow MRI) has gained an increasing interest over the last years and stands out as a highly relevant tool for diagnosis, patient follow-up and research in cardiovascular diseases. On top of providing a non-invasive access to the 3D velocity field in-vivo, this technique allows retrospective quantification of velocity-derived hemodynamic biomarkers such as relative pressure or shear stress, which are pertinent for medical diagnosis but difficult to measure in practice. However, several acquisition parameters (spatio-temporal resolution, encoding velocity, imaging artifacts) might limit the expected accuracy of the measurements and potentially lead to erroneous diagnosis. Moreover, the intrinsic complexities of the MRI acquisition process make it generally difficult to localize the sources of measurement errors.This thesis aims at developing a methodology for the assessment of 4D Flow MRI measurements in complex flow configuration. A well-controlled experiment gathering an idealized in-vitro flow phantom generating flow structures typical of that observed in the cardiovascular system is designed. The flow is simultaneously predicted by means of a high-order Computational Fluid Dynamics (CFD) solver and measured with 4D flow MRI. By evaluating the differences between the two modalities, it is first shown that the numerical solution can be considered very close to the ground truth velocity field. The analysis also reveals the typical errors present in 4D flow MRI images, whether relevant to the velocity field itself or to classical derived quantities (relative pressure, wall shear stress). Finally, a 4D Flow MRI simulation framework is developed and coupled with CFD to reconstruct the synthetic MR images of the reference flow that correspond to the acquisition protocol, but exempted from experimental measurement errors. Thanks to this new capability, the sources of the potential errors in 4D Flow MRI (hardware, software, sequence) can be identified
Audebert, Chloé. „Mathematical liver modeling : hemodynamics and function in hepatectomy“. Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066077/document.
Der volle Inhalt der QuelleMajor liver resection is being performed to treat liver lesions or for adult-to-adult living donor liver transplantation. Complications of these surgeries are related to a poor liver function. The links between liver hemodynamics, liver volume and liver function remain unclear and are important to better understand these complications. The surgery increases the resistance to blood flow in the organ, therefore it modifies liver hemodynamics. Large modifications of the portal vein hemodynamics have been associated with poor liver regeneration. Moreover the liver receives 25% of the cardiac outflow, therefore liver surgery may impact the whole blood circulation. In this context, the first goal is to investigate with mathematical models the impact of liver surgery on liver hemodynamics. The second goal is to study the liver perfusion and function with mathematical models. The first part describes the experimental conditions and reports the measurements recorded. Then, the second part focuses on the liver hemodynamics during partial hepatectomy. On one hand, the hemodynamics during several surgeries is quantitatively reproduced and explained by a closed-loop model based on ODE. On the other hand, the change of waveforms observed after different levels of liver resection is reproduced with a model of the global circulation, including 0D and 1D equations. This may contribute to a better understanding of the change of liver architecture induced by hepatectomy. Next, the transport in blood of a compound is studied. And a pharmacokinetics model and its parameter identification are developed to quantitatively analyze indocyanine green fluorescence dynamics in the liver tissue
Vergeur-Laborie, Valérie. „Simulation numérique de l'écoulement artériel cérébral : contribution à l'étude des conséquences hémodynamiques des sténoses situées en amont et en aval du polygone de Willis“. Toulouse 3, 1993. http://www.theses.fr/1993TOU30168.
Der volle Inhalt der QuelleBachelet, Caroline. „Une méthode de détermination indirecte de la rhéologie d'un fluide en écoulement par des mesures de profils de vitesse“. Paris 7, 2001. http://www.theses.fr/2001PA077163.
Der volle Inhalt der QuelleCros, François. „Confluences, remplissage et vidange : deux aspects singuliers du réseau veineux jambier“. Paris 7, 2003. https://tel.archives-ouvertes.fr/tel-00004089.
Der volle Inhalt der QuelleZenses, Anne-Sophie. „Performance hémodynamique de prothèses valvulaires aortiques percutanées et stratégies d'implantation lors de procédures "valve-in-valve" : études in vitro et in vivo“. Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0417/document.
Der volle Inhalt der QuelleTranscatheter aortic valve implantation (TAVI) has emerged as an alternative to surgery for patients with severe aortic stenosis and high surgical risk. This technique is extending to a wider population (e.g. with more complex anatomy or lower surgical risk), as well as to patients with degenerated surgical bioprostheses (BPs). However, two major concerns remain limiting. Regarding “classical TAVI”, periprosthetic leaks have been associated with increased mortality. Oversizing is used to secure the device within the aortic annulus which is often non circular. The effects of oversizing and annulus shape on the hemodynamic performance are unknown. Regarding ViV implantations, elevated post-procedural gradients are common and have been associated with increased mortality. The principal factors associated with this residual stenosis as well as with increased risk of mortality, have been BPs label size ≤ 21 mm and mode of failure by stenosis. These factors are not specific enough and there is currently no recommendation for the treatment of small BPs. Besides, the actual hemodynamic benefit associated with ViV has not been evaluated (vs. pre ViV status).The general objective of this work is to understand the interactions between the transcatheter prosthesis and the aortic annulus or the BP to be treated, which impact the hemodynamic performance, especially in complex conditions of implantation, in order to extend the indications of TAVI. In the context of ViV, the objective is to specify the factors associated with the hemodynamic performance and utility of the treatment. The final aim is to provide strategies of implantation in order to optimize the success of the procedure
Sala, Lorenzo. „Modélisation mathématique et simulation de flux sanguins oculaires et leur interactions“. Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAD021.
Der volle Inhalt der QuelleOptic neuropathies such as glaucoma are often late-onset, progressive and incurable diseases. Despite the recent progress in clinical research, there are still numerous open questions regarding the etiology of these disorders and their pathophysiology. Furthermore, data on ocular posterior tissues are difficult to estimate noninvasively and their clinical interpretation remains challenging due to the interaction among multiple factors that are not easily isolated. The recent use of mathematical models applied to biomedical problems has helped unveiling complex mechanisms of the human physiology. In this very compelling context, our contribution is devoted to designing a mathematical and computational model coupling tissue perfusion and biomechanics within the human eye. In this thesis we have developed a patient-specific Ocular Mathematical Virtual Simulator (OMVS), which is able to disentangle multiscale and multiphysics factors in a accessible environment by employing advanced and innovative mathematical models and numerical methods. Moreover, the proposed framework may serve as a complementary method for data analysis and visualization for clinical and experimental research, and a training application for educational purposes
This, Alexandre. „Image/Model Fusion for the Quantification of Mitral Regurgitation Severity“. Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS384.
Der volle Inhalt der QuelleThe regular supply of nutrients and oxygen to the organs is ensured by the regular contraction of the heart, a major organ of the cardiovascular system. As a result of certain cardiac diseases, cardiac valves may not function properly, which can lead to a retrograde flow of blood. In the case of the mitral valve, located between the left ventricle and the left atrium, it is referred to as mitral regurgitation. It is necessary to quantify the severity of mitral regurgitation in order to propose an appropriate treatment. In the first part of this document, a 3D mathematical model of cardiac hemodynamics is developed and integrates a mitral regurgitation model. We will also take the opportunity to model the isovolumetric phases of the heart. A relatively accurate model of cardiac hemodynamics, but nevertheless reasonable in term of numerical complexity, is thus obtained at the end of this first part. The second part of this document describes the strategy adopted to allow the fusion of medical images with the numerical simulations. An automatic method allowing the personalization of the mathematical model developed in the first part of the manuscript, based on medical images, is presented, allowing a systematic evaluation of the PISA method. Finally, as the methods presented are still too expensive from a numerical point of view, we conclude with the presentation of a blood flow reconstruction method combining Color Doppler images with physical constraints related to blood incompressibility
Boilevin-Kayl, Ludovic. „Modeling and numerical simulation of implantable cardiovascular devices“. Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS039.
Der volle Inhalt der QuelleThis thesis, taking place in the context of the Mivana project, is devoted to the modeling and to the numerical simulation of implantable cardiovascular devices. This project is led by the start-up companies Kephalios and Epygon, conceptors of minimally invasive surgical solutions for the treatment of mitral regurgitation. The design and the simulation of such devices call for efficient and accurate numerical methods able to correctly compute cardiac hemodynamics. This is the main purpose of this thesis. In the first part, we describe the cardiovascular system and the cardiac valves before presenting some standard material for the mathematical modeling of cardiac hemodynamics. Based on the degree of complexity adopted for the modeling of the valve leaflets, two approaches are identified: the resistive immersed surfaces model and the complete fluidstructure interaction model. In the second part, we investigate the first approach which consists in combining a reduced modeling of the valves dynamics with a kinematic uncoupling of cardiac hemodynamics and electromechanics. We enhance it with external physiological data for the correct simulation of isovolumetric phases, cornerstones of the heartbeat, resulting in a relatively accurate model which avoids the complexity of fully coupled problems. Then, a series of numerical tests on 3D physiological geometries, involving mitral regurgitation and several configurations of immersed valves, illustrates the performance of the proposed model. In the third and final part, complete fluid-structure interaction models are considered. This type of modeling is necessary when investigating more complex problems where the previous approach is no longer satisfactory, such as mitral valve prolapse or the closing of a mechanical valve. From the numerical point of view, the development of accurate and efficient methods is mandatory to be able to compute such physiological cases. We then consider a complete numerical study in which several unfitted meshes methods are compared. Next, we present a new explicit coupling scheme in the context of the fictitious domain method for which the unconditional stability in the energy norm is proved. Several 2D numerical examples are provided to illustrate the properties and the performance of this scheme. Last, this method is finally used for 2D and 3D numerical simulation of implantable cardiovascular devices in a complete fluid-structure interaction framework
Smaldone, Saverio. „Analyse numérique et simulations de problèmes couplés pour le système cardiovasculaire“. Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066505.
Der volle Inhalt der QuelleIn this thesis we present the numerical analysis and the development of parti- tioned algorithms in order to couple the blood dynamics in different cardiovascular compart- ments (3D-3D, 3D-0D). In the first part a fluid-fluid coupled problem is introduced. On the interface between the domains Robin-Robin boundary conditions, derived from the interface Nitsche’s formulation, are considered. We suggest different staggered explicit schemes whose stability is analyzed in the energy norm. Extensive numerical experiments illustrate the accuracy of the methods presented. The second part deals with more realistic cardiovascular applications. First a reduced order model for the heart valves is described. Without dealing with fluid-structure interaction with the blood flow, the valves are replaced by immersed surfaces acting as resistances on the fluid. Numerical simulations show the efficiency and the robustness of this model in the framework of a fluid-fluid interaction scheme. In the end, an ALE formulation is used to solve a fluid model in a moving domain. We show that adding a suitable consistent term, a stable energy inequality can be obtained without considering any Geometric Conservation Laws. The work ends with numerical sim- ulations on blood dynamics in the left ventricle coupled with the blood flowing in the aorta
Zhang, Hengdi. „Simulation de la microcirculation sanguine et son couplage à la signalisation biochimique“. Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAY072/document.
Der volle Inhalt der QuelleBlood flow in microcirculation is vital for oxygen, carbon dioxide and nutrients transport. Most of blood cells are red blood cells (RBCs), so that by blood flow we mean flow of a suspension of RBCs. For long time blood flow has been mainly considered as a passive phenomenon, in which RBCs are viewed as passive carriers of oxygen. The modern view is completely different: blood flow is more active than we thought. The RBCs as well as vascular endothelial cells covering the internal walls of blood vessels are involved in a number of biochemical signaling processes that are triggered by shear stress eliciting a number of biochemical events, and ultimately resulting into vasomotor regulation without participation of the nerve system. For example, RBCs do not only carry oxygen but also ATP (adenosine triphosphate) , the release of which occurs thanks to changes of RBC membrane protein conformations caused by shear stress. Released ATP reacts with some endothelial membrane receptors leading to vasodilation. This thesis is devoted to blood flow and its coupling to biochemical signaling. More precisely, we investigate i) the dynamics of RBCs, ii) the advection diffusion of chemicals in blood flow and the role of iii) the geometry of vessel networks, in the mentioned signaling processes in microcirculations. Firstly, we study the RBC dynamics in a pipe flow with realistic viscosity contrast values, where a link between shape dynamics and rheology is established. Secondly, we develop an advection-diffusion solver that can handle general moving curved boundaries based on lattice-Boltzmann method (LBM); we then implement it for the study of the problem of ATP release from RBCs under shear flow. Membrane tension and deformation induced by shear stress together with vessel network geometry contribute to ATP release. Finally we demonstrate the capability of applying our model and our numerical tool to the complete problem of blood under flow involving ATP release from RBCs and endothelial calcium signaling as a preliminary step to the ambitious task of mechano-involved local regulation events in microcirculation
Bouaou, Kevin. „Apport de la mécanique des fluides dans l'étude des flux sanguins aortiques“. Electronic Thesis or Diss., Sorbonne université, 2020. http://www.theses.fr/2020SORUS076.
Der volle Inhalt der QuelleAging is associated with morphological, functional and hemodynamic changes in the arterial system, most often aggravated by cardiovascular disease. Understanding these aggravating interactions is important to reduce patients risk. Medical imaging plays a major role in this context through modalities such as velocity encoding MRI combined with quantitative image processing and computational resolution of Navier-Stokes equations that govern blood flow hemodynamics. The aim of this thesis is to develop and combine image processing methods dedicated to 4D flow MRI data analysis with computational fluid dynamics to extract quantitative biomarkers such as intra-aortic pressure fields and their spatio-temporal propagations, aortic wall shear stress and intra-aortic vorticity. We have demonstrated the ability of these biomarkers to detect age-related sub-clinical aortic impairment and to characterize pathological aortic dilatation. In addition, association of spatio-temporal aortic pressure distributions with vortex occurrence and duration as well as with wall shear stress were studied. In a second work, we developed a numerical simulation software to solve the Navier-Stokes system using finite element models. An iterative projection method was applied to 2D and 3D vessel stenosis models as well as to 3D geometrical aortic models resulting from segmentation to validate our implementation. Finally, a preliminary work applying our numerical model to patient-specific geometries was performed revealing encouraging associations between simulated data and MRI measures
Kerbeci, Pascaline. „Quantification de l'atrophie musculaire, du contenu hydrique et de la distensibilité veineuse des membres inférieurs : effet sur la tolérance orthostatique : bed rest avec et sans countremesures [sic]“. Tours, 2006. http://www.theses.fr/2006TOUR3301.
Der volle Inhalt der Quelle24 women were placed in bed rest (60 d) to quantify few elements of physiological adaptation and deconditioning. Ultrasounds scanner was validated by MRI. After 55 d of bed rest, left ventricular myocardial mass and diastolic volume, thigh muscles volume decrease, venous distensibility of lower limbs, evaluated during orthostatic tests, increases in nutrition and control groups. Exercise countermeasure limits alteration of these parameters. Liquid content in venous network and tissues of lower limbs decreases. No countermeasure limits the variation of liquid content. These modifications were superior in tolerant subjects during TILT. These elements are modified by Bed rest and contribute probably to orthostatic intolerance. Exercise countermeasure reduces some of these elements, without limiting totally orthostatic intolerance after Bed rest
Lal, Rajnesh. „Data assimilation and uncertainty quantification in cardiovascular biomechanics“. Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTS088/document.
Der volle Inhalt der QuelleCardiovascular blood flow simulations can fill several critical gaps in current clinical capabilities. They offer non-invasive ways to quantify hemodynamics in the heart and major blood vessels for patients with cardiovascular diseases, that cannot be directly obtained from medical imaging. Patient-specific simulations (incorporating data unique to the individual) enable individualised risk prediction, provide key insights into disease progression and/or abnormal physiologic detection. They also provide means to systematically design and test new medical devices, and are used as predictive tools to surgical and personalize treatment planning and, thus aid in clinical decision-making. Patient-specific predictive simulations require effective assimilation of medical data for reliable simulated predictions. This is usually achieved by the solution of an inverse hemodynamic problem, where uncertain model parameters are estimated using the techniques for merging data and numerical models known as data assimilation methods.In this thesis, the inverse problem is solved through a data assimilation method using an ensemble Kalman filter (EnKF) for parameter estimation. By using an ensemble Kalman filter, the solution also comes with a quantification of the uncertainties for the estimated parameters. An ensemble Kalman filter-based parameter estimation algorithm is proposed for patient-specific hemodynamic computations in a schematic arterial network from uncertain clinical measurements. Several in silico scenarii (using synthetic data) are considered to investigate the efficiency of the parameter estimation algorithm using EnKF. The usefulness of the parameter estimation algorithm is also assessed using experimental data from an in vitro test rig and actual real clinical data from a volunteer (patient-specific case). The proposed algorithm is evaluated on arterial networks which include single arteries, cases of bifurcation, a simple human arterial network and a complex arterial network including the circle of Willis.The ultimate aim is to perform patient-specific hemodynamic analysis in the network of the circle of Willis. Common hemodynamic properties (parameters), like arterial wall properties (Young’s modulus, wall thickness, and viscoelastic coefficient) and terminal boundary parameters (reflection coefficient and Windkessel model parameters) are estimated as the solution to an inverse problem using time series pressure values and blood flow rate as measurements. It is also demonstrated that a proper reduced order zero-dimensional compartment model can lead to a simple and reliable estimation of blood flow features in the circle of Willis. The simulations with the estimated parameters capture target pressure or flow rate waveforms at given specific locations
Lecarpentier, Edouard. „Etude des flux sanguins dans le placenta humain et influence du shear stress sur la fonction biologique du syncytiotrophoblaste“. Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCB052/document.
Der volle Inhalt der QuelleHuman placentation is hemomonochorial, maternal blood circulates in direct contact with the syncytiotrophoblast. In the intervillous space, the maternal blood exerts frictional mechanical forces (shear stress) on the microvillous surface of the syncytiotrophoblast. Flowing blood constantly exerts a shear stress, on the endothelial cells lining blood vessel walls, and the endothelial cells respond to shear stress by changing their morphology, function, and gene expression. The effects of shear stress on the human syncytiotrophoblast and its biological functions have never been studied. The objectives of this study were (1) to determine in silico the physiological values of shear stress exerted on human syncytiotrophoblast during normal pregnancies, (2) to develop a model reproducing in vitro the shear stress on human syncytiotrophoblast and (3) to study in vitro the biological response of human syncytiotrophoblast to shear stress. The 2D numerical simulations showed that the shear stress applied to the syncytiotrophoblast is highly heterogeneous in the intervillous space. In spite of high intraplacental maternal blood flow rates (400-600mL.min-1), the estimated average values of shear stress are relatively low (0.5±0.2 to 2.3±1.1 dyn.cm-2). To study the shear stress-induced cellular responses during exposure times ranging from 5 minutes to 24 hours we have developed two dynamic cell culture models adapted to the human syncytiotrophoblast. We found no evidence of decreased cell viability or early processes of apoptosis in dynamic conditions (1 dyn.cm-2, 24h) compared to static conditions. Shear stress (1 dyn.cm-2) triggers intracellular calcium flux, which increases the synthesis and release of PGE2. The enhanced intracellular cAMP in FSS conditions was blocked by COX1/COX2 inhibitors, suggesting that the increase in PGE2 production could activate the cAMP/PKA pathway in an autocrine/paracrine fashion. FSS activates the cAMP/PKA pathway leading to upregulation of PlGF in human STB. Shear stress-induced phosphorylation of CREB and upregulation of PlGF were prevented by inhibition of PKA with H89 (3 μM). The syncytiotrophoblast of the human placenta is a mechanosenstive tissue
Decorato, Iolanda. „Simulation numérique des interactions fluide-structure dans une fistule artério-veineuse sténosée et des effets de traitements endovasculaires“. Phd thesis, Université de Technologie de Compiègne, 2013. http://tel.archives-ouvertes.fr/tel-00832342.
Der volle Inhalt der QuelleCROS, François. „Confluences, remplissage et vidange: deux aspects singuliers du système veineux jambier“. Phd thesis, Université Paris-Diderot - Paris VII, 2003. http://tel.archives-ouvertes.fr/tel-00004089.
Der volle Inhalt der QuelleBresson, Damien. „Étude de l’écoulement sanguin dans un anévrysme intracrânien avant et après traitement par stent flow diverter : quantification par traitement d’images de séquences angiographiques 2D“. Thesis, Compiègne, 2016. http://www.theses.fr/2016COMP2308/document.
Der volle Inhalt der QuelleIntracranial aneurysms treatment based on intra aneurismal flow modification tend to replace traditionally coiling in many cases and not only complex aneurysms for which they were initially designed. Dedicated stents (low porosity, high pores density stents) called “flow diverter” stents are deployed across the neck of the aneurysm to achieve this purpose. The summation of three different mechanisms tend to lead to the healing of the aneurysm: immediate flow alteration due to the mechanical screen effect of the stent, physiological triggering of acute or progressive thrombus formation inside the aneurysm’s pouch and long term biological response leading in neointima formation and arterial wall remodeling. This underlying sequence of processes is also supposed to decrease the recanalization rate. Scientific data supporting the flow alteration theory are numerous and especially computational flow dynamics (CFD). These approaches are very helpful for improving biomechanical knowledge of the relations between blood flow and pathology, but they do not fit in real-time treatments. Neuroendovascular treatments are performed under dynamic x-ray modality (digital subtracted angiography a DSA-).However, in daily practice, FD stents are sized to the patient’s 3D vasculature anatomy and then deployed. The flow modification is then evaluated by the clinician in an intuitive manner: the decision to deploy or not another stent is based solely on a visual estimation. The lack of tools available in the angioroom for quantifying in real time the blood flow hemodynamics should be pointed out. It would make sense to take advantage of functional data contained in contrast bolus propagation and not only anatomical data. Thus, we proposed to create flow software based on angiographic analysis. This software was built using algorithms developed and validated on 2D-DSA sequences obtained in a swine intracranial aneurysm model. This intracranial animal model was also optimized to obtain 3D vascular imaging and experimental hemodynamic data that could be used to realize realistic computational flow dynamic. In a third step, the software tool was used to analyze flow modification from angiographic sequences acquired during unruptured IA from patients treated with a FD stent. Finally, correlation between flow change and aneurysm occlusion at long term follow-up with the objective of identifying predictive markers of long term occlusion was performed
Joly, Florian. „Numerical Insights for AAA Growth Understanding and Predicting: Morphological and Hemodynamic Risk Assessment Features and Transient Coherent Structures Uncovering“. Thèse, 2019. http://hdl.handle.net/1866/22597.
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