Dissertations / Theses on the topic 'Hemodynamic Simulations'
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Boutsianis, Evangelos. "Anatomically accurate hemodynamic simulations in the aorta and the coronary arteries /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16996.
BOTTI, Lorenzo Alessio (ORCID:0000-0002-0511-9022). "Galerkin methods for incompressible fluid flow simulations: application to hemodynamics." Doctoral thesis, Università degli studi di Bergamo, 2010. http://hdl.handle.net/10446/610.
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.
This 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
Davis, Timothy L. (Timothy Lloyd). "Teaching physiology through interactive simulation of hemodynamics." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13823.
Zimny, Simon [Verfasser]. "Hemodynamic Flow Simulation in Patient Specific Cerebral Aneurysms / Simon Zimny." München : Verlag Dr. Hut, 2016. http://d-nb.info/1106592565/34.
Aletti, Matteo Carlo Maria. "Mathematical modelling and simulations of the hemodynamics in the eye." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066031/document.
The 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
Yu, Xiaohong, and 于曉紅. "Hemodynamic analysis of blood flows in carotid bifurcations." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B3864700X.
Audebert, Chloé. "Mathematical liver modeling : hemodynamics and function in hepatectomy." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066077/document.
Major 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
Lal, Rajnesh. "Data assimilation and uncertainty quantification in cardiovascular biomechanics." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTS088/document.
Cardiovascular 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
He, Xiaoyi. "Numerical simulations of blood flow in human coronary arteries." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/16685.
LeSage, Susan. "Central and peripheral hemodynamic responses to a tilt table simulation of -/+ Gz transitions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ39205.pdf.
MOHAMMADYARI, Parvin. "Advanced Human Hemodynamic Modelling and Valuation using MRI imaging." Doctoral thesis, Università degli studi di Ferrara, 2021. http://hdl.handle.net/11392/2487973.
Sharma, Monita. "Simulating hemodynamics in in vitro culture models: Implications on Nano-biointeractions." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1388681297.
wang, zhiqiang. "STUDYING COMPUTATIONAL METHODS FOR BIOMEDICAL GEOMETRY EXTRACTION AND PATIENT SPECIFIC HEMODYNAMICS." Kent State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=kent1493042299659479.
Damián, Ares Gonzalo. "Integrative computational modeling & in-vivo characterization of residual deformations in hemodynamics." Laboratório Nacional de Computação Científica, 2016. https://tede.lncc.br/handle/tede/230.
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Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)
This thesis is concerned with two major problems arising in the modeling of the cardiovascular system. The first topic consists in a comprehensive approach for the simulation of arterial blood flow and its effect on the stress state of the arterial wall, and the second topic is concerned with the in-vivo characterization of residual deformations in arterial wall tissues, based on data provided by medical images. Specifically, regarding the first topic, an original modeling framework is proposed for the treatment of hemodynamic problems with increased realism, featuring a combination of several modeling techniques in order to account for i) the fact that the initial (image-based) geometry corresponds to a configuration which is at equilibrium with an internal pressure acting over the lumen, and with tethering forces located at the artificial (axial) boundaries delimiting the arterial region of interest; ii) the fluid-structure interaction problem; iii) the complex constitutive behavior of the arterial wall; iv) the influence of surrounding tissues; v) the interaction of the vessel with the rest of the cardiovascular system; and iv) the influence of residual stresses. In order to tackle the issues described above, the preload mechanical problem is solved in a first stage, finding the zero-load material configuration which is employed to define suitable constitutive equations. This is performed by finding the solution for the mechanical equilibrium of the given image configuration considering the vessel at this state to be loaded by an internal baseline pressure and an axial traction (caused by tethering forces) at the artificial boundaries. It is worthwhile to mention that this axial traction is such that a previously defined pre-stretch level is considered on the equilibrium image configuration. Once the reference configuration is obtained, the complete 3D fluid-structure interaction simulation is carried out, coupled with a dimensionally reduced 1D model of the rest of the cardiovascular system. Strong coupling via fixed-point iterations is achieved for the fluid-structure interaction, while the dimensionally heterogeneous coupling is achieved through a Broyden method. Regarding the constitutive modeling, a fiber-reinforced hyperelastic constitutive law is considered. Furthermore, through the analysis of several numerical examples, the sensitivity with respect to the existence of the preload stresses is assessed to quantify the importance of this issue. These results indicate that the stress state of the arterial wall is strongly influenced by the existence of preload. Therefore, the consideration of such preload state is mandatory for the prediction of stresses in arterial tissue. For the second topic, a conceptual framework is presented for the in-vivo estimation of residual deformations and stresses. As a given data, a set of known configurations for an arterial segment is considered, which can potentially be obtained from medical imaging techniques. The mechanical equilibrium equations corresponding to such configurations are introduced through a variational approach, highlighting the role of the residual deformations and associated stresses. In this context, a cost functional is proposed to measure the imbalance of the mechanical setting arising from the consideration of inconsistent residual deformations, based on the generalized residuals of the associated variational equations. Then, the characterization of residual deformations becomes an optimization problem, focused on the minimization of this cost functional. For this purpose, a simple gradient descent method and an interior-point algorithm for constrained optimization are explored in this work. The proposed methodology is tested using three numerical examples based on manufactured solutions, a simple clamped bar, a thick-walled cylinder and a three-layered aorta artery. The obtained results are promising and suggest that the present method (or variants based on the present ideas), when coupled with adequate image acquisition techniques, could successfully lead to the in-vivo identification of residual deformations.
Esta tese aborda dois problemas de relevância na modelagem do sistema cardiovascular humano. O primeiro tema consiste no desenvolvimento de um enfoque abrangente para a simulação do escoamento sanguíneo e sua interação com a parede arterial, e o segundo tópico é a caracterização in-vivo de tensões e deformações residuais na parede arterial baseada em dados fornecidos por imagens médicas. De maneira específica, em relação ao primeiro tópico, um marco de modelagem é proposto para o tratamento de problemas hemodinâmicos com um alto grau de realismo, apresentando uma combinação de diferentes técnicas de modelagem para levar em conta i) o fato que as geometrias iniciais obtidas a partir de imagens médicas são correspondentes a um sistema de carregamentos não nulos, definido pela existência da pressão interna no lumen e de tensões axiais localizadas nos contornos artificiais do segmento arterial; ii) o problema de interação fluido-estrutura; iii) o complexo comportamento constitutivo da parede arterial; iv) a interação do segmento de interesse com o resto do sistema cardiovascular; e v) a influência dos tecidos circundantes; e vi) a existência de tensões residuais. Para a abordagem das questões descritas acima, o problema mecânico de precarregamento é resolvido em uma primeira etapa, encontrando a configuração material de carregamento nulo onde as equações constitutivas são usualmente definidas. Isto é realizado encontrando a solução do problema de equilíbrio mecânico da estrutura arterial dada, considerando que o vaso está submetido a um nível de pressão de base e uma tração axial nos contornos artificiais. Vale a pena ressaltar que esta tração axial é correspondente a um nível de pre-estiramento previamente definido. Uma vez que a configuração de referência é obtida, a simulação fluido-estrutura 3D é realizada, acoplada com um modelo dimensionalmente reduzido do resto do sistema cardiovascular. Um acoplamento forte através de iterações de ponto fixo é empregado para representar a interação fluido-estrutura, equanto o acoplamento entre modelos dimensionalmente heterogêneos é conseguido usando um método tipo Broyden. Em relação à modelagem constitutiva, um modelo hyperelástico reforçado com fibras é considerado. Além disso, através da análise de vários exemplos numéricos, a sensibilidade com relação à existência de precarregamentos é quantificada para remarcar a relevância desta questão. Tais resultados indicam que o estado de tensão da parede arterial é fortemente influenciado pela existência de precarregamentos. Assim sendo, levar em consideração esse estado de precarga é fundamental para a predição de tensões no tecido arterial. Em relação ao segundo tópico, um marco conceptual é apresentado para estimação de tensões e deformações residuais. Consideramos que os dados são um conjunto de configurações de um segmento arterial, as quais poderiam ser obtidas a partir do uso de técnicas de adquisição e , processamento e segmentação de imagens. Utilizando um enfoque variacional, são apresentadas as equações de equilíbrio mecânico para as configurações conhecidas, acentuando o papel desempenhado pelas deformações residuais. Neste contexto, apresenta-se um funcional custo que mede o desbalance mecânico que é originado se um campo de deformações residuais inconsistente é admitido. Este funcional custo está baseado no resíduo generalizado das equações variacionais previamente mencionadas. Como consequência, o problema de estimação de deformações residuais é transformado em um problema de otimização, no qual se procura minimizar o funcional custo proposto. Com este objetivo, neste trabalho de tese são considerados dois métodos, um método de gradiente e um algoritmo de ponto interior para problemas que apresentam restrições. A metodologia proposta é testada em três exemplos numéricos baseados em soluções manufaturadas: um barra engastada, um cilindro de parede grossa, e uma artéria aorta composta por três camadas. Os resultados obtidos são promissores e sugerem que o método apresentado (ou variantes baseadas nas ideias aqui mostradas) junto com técnicas adequadas para a adquisição de imagens podem conduzir à identificação in-vivo de deformações residuais.
Yu, Hongtao. "Multiscale Modeling of Hemodynamics in Human Vessel Network and Its Applications in Cerebral Aneurysms." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1526905279931141.
Reasor, Daniel Archer. "Numerical simulation of cellular blood flow." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42760.
Suo, Jin. "Investigation of blood flow patterns and hemodynamics in the human ascending aorta and major trunks of right and left coronary arteries using magnetic resonance imaging and computational fluid dynamics." Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-01192005-121529/unrestricted/suo%5Fjin%5F200505%5Fphd.pdf.
Giddens, P. Don, Committee Chair ; Vito, P. Raymond, Committee Member ; Taylor, Robert, W., Committee Member ; Oshinski, John, Committee Member ; Bao, Gang, Committee Member. Includes bibliographical references.
Spiegel, Martin [Verfasser], and Joachim [Akademischer Betreuer] Hornegger. "Patient-Specific Cerebral Vessel Segmentation with Application in Hemodynamic Simulation = Patientenindividuelle zerebrale Gefäßsegmentierung mit Anwendung in der Blutflusssimulation / Martin Spiegel. Betreuer: Joachim Hornegger." Erlangen : Universitätsbibliothek der Universität Erlangen-Nürnberg, 2011. http://d-nb.info/1015474489/34.
Drapeau, Guy. "Comparative numerical study of the intra-vessel flow characteristics between a flat and a cylindrical configuration in a stented wall region." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112566.
The spatial and temporal distribution of the Wall Shear Stress (WSS), which is believed to be of primary importance in the development of restenosis should be comparable between the flat and the cylindrical stent configuration models. The velocity and shear strain rate distributions will be compared between the flat and cylindrical stent configurations using computational fluid dynamics (CFD) simulations in order to analyse the feasibility of using a flat instead of a cylindrical version of the stent model for PIV experiments. It will be shown that for a physiological pulsatile flow the flat model yields results in shear strain rate spatial and temporal distribution that is comparable to the cylindrical model. A more PIV compatible, efficient and less refractive error prone validated flat model would be advantageous when several stent designs influence on the local hemodynamics around the strut geometries have to be studied quantitatively and optimized.
Yamabe, Paulo Vinícius Miyuki. "Study of a methodology to evaluate the severity of obstructed coronary arteries with the aid of computer simulations." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-12122016-095324/.
Simulações computacionais tornaram-se uma excelente ferramenta para auxiliar a área médica. O presente trabalho é um estudo de uma metodologia não invasiva para avaliar a importância hemodinâmica de artérias coronárias com estenose através do uso de simulações computacionais. A severidade da lesão da artéria é avaliada através do Fractional Flow Reserve, calculado pelo gradiente de pressão antes e depois da lesão. Os modelos geométricos computacionais foram obtidos a partir de imagens médicas de exames de Angiografia por Tomografia Computadorizada e as simulações consideram o fluxo pulsátil e as propriedades não-Newtonianas do sangue. As equações governantes do fluxo de sangue são resolvidas utilizando o Método dos Elementos Finitos aplicado ao método numérico chamado Incremental Pressure Correction Scheme, e com o uso de bibliotecas do programa em código aberto FEniCS. Foram realizados simulações de três pacientes e os resultados foram confrontados com as medidas invasivas do FFR. A metodologia proposta mostrou-se viável para o estudo e análise de coronárias com estenose.
Wake, Amanda Kathleen. "Modeling Fluid Mechanics in Individual Human Carotid Arteries." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7562.
Maksuti, Elira. "Imaging and modeling the cardiovascular system." Doctoral thesis, KTH, Medicinsk bildteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-196538.
QC 20161115
Diourté, Badié. "Modélisation et simulation du système cardio-vasculaire par analogie électrique." Grenoble 1, 1998. http://www.theses.fr/1998GRE10222.
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.
Puiseux, Thomas. "Numerical simulations for phase-contrast magnetic resonance imaging." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS109.
Hemodynamics (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
Kemp, Iain Henry. "Development,testing and fluid interaction simulation of a bioprosthetic valve for transcatheter aortic valve implantation." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71710.
ENGLISH ABSTRACT: Bioprosthetic heart valves (BHVs) for transcatheter aortic valve implantation (TAVI) have been rapidly developing over the last decade since the first valve replacement using the TAVI technique. TAVI is a minimally invasive valve replacement procedure offering lifesaving treatment to patients who are denied open heart surgery. The biomedical engineering research group at Stellenbosch University designed a 19 mm balloon expandable BHV for TAVI in 2007/8 for testing in animal trials. In the current study the valve was enlarged to 23 mm and 26 mm diameters. A finite element analysis was performed to aid in the design of the stents. New stencils were designed and manufactured for the leaflets using Thubrikar‟s equations as a guide. The 23 mm valve was manufactured and successfully implanted into two sheep. Fluid structure interaction (FSI) simulations constitute a large portion of this thesis and are being recognized as an important tool in the design of BHVs. Furthermore, they provide insight into the interaction of the blood with the valve, the leaflet dynamics and valve hemodynamic performance. The complex material properties, pulsating flow, large deformations and coupling of the fluid and the physical structure make this one of the most complicated and difficult research areas within the body. The FSI simulations, of the current valve design, were performed using a commercial programme called MSC.Dytran. A validation study was performed using data collected from a cardiac pulse duplicator. The FSI model was validated using leaflet dynamics visualisation and transvalvular pressure gradient comparison. Further comparison studies were performed to determine the material model to be used and the effect of leaflet free edge length and valve diameter on valve performance. The results from the validation study correlated well, considering the limitations that were experienced. However, further research is required to achieve a thorough validation. The comparative studies indicated that the linear isotropic material model was the most stable material model which could be used to simulate the leaflet behaviour. The free edge length of the leaflet affects the leaflet dynamics but does not greatly hinder its performance. The hemodynamic performance of the valve improves with an increase in diameter and the leaflet dynamics perform well considering the increased surface area and length. Many limitations in the software prevented more accurate material models and flow initiation to be implemented. These limitations significantly restricted the research and confidence in the results. Further investigation regarding the implementation of FSI simulations of a heart valve using the commercial software is recommended.
AFRIKAANSE OPSOMMING: Bio-prostetiese hartkleppe (Bioprosthetic Heart Valves - BHVs) wat gebruik word vir transkateter aortaklep-inplantings (Transcatheter Aortic Valve Implantation - TAVI) het geweldig vinnige ontwikkeling getoon in die afgelope tien jaar sedert die eerste klepvervanging wat van die TAVI prosedure gebruik gemaak het. TAVI is ʼn minimaal indringende klepvervangingsprosedure wat lewensreddende behandeling bied aan pasiënte wat ope-hart sjirurgie geweier word. Die Biomediese Ingenieurswese Navorsingsgroep (BERG) by Stellenbosch Universiteit het in 2007/8 ʼn 19 mm ballon-uitsetbare BHV vir TAVI ontwerp vir eksperimente met diere, en hierdie tesis volg op die vorige projekte. In die huidige studie is die klep vergroot na 23 mm en 26 mm in deursnee. ʼn Eindige element analise is gedoen om by te dra tot die ontwerp van die rekspalke vir die klep. Nuwe stensils is ontwerp en vervaardig vir die klepsuile, deur gebruik te maak van Thubrikar se vergelykings. Die 23 mm klep is vervaardig en suksesvol in twee skape ingeplant. Vloeistruktuur interaksie (Fluid Structure Interaction (FSI)) simulasies vorm ‟n groot deel van die tesis en word gesien as ʼn noodsaaklike hulpmiddel in die ontwerp van BHVs. Die simulasies verskaf ook insig in die interaksie van die bloed met die klep, die klepsuil-dinamika en die klep se hemodinamiese werkverrigting. Die komplekse materiaal eienskappe, polsende vloei, grootskaalse vervorming, die verbinding van die vloeistof en die fisiese struktuur maak van hierdie een van die mees gekompliseerde voorwerpe om te simuleer. Die FSI simulasies van die huidige ontwerp, is uitgevoer deur van kommersiële sagteware, MSC.Dytran, gebruik te maak. ʼn Geldigheidstudie wat data gebruik het vanaf die hartklop-nabootser, is uitgevoer. Die FSI model word geverifieer deur klepsuil dinamika visualisering en ʼn vergelyking van die drukgradiënt gebruik te maak. Verdere vergelykende studies is uitgevoer om te bepaal watter materiaal model om te gebruik, asook die uitwerking van die klepsuil-vrye rand en klepdeursnee op die klep se werkverrigting. Die resultate van die studie korreleer goed, in ag genome die beperkings wat ervaar is. Verdere navorsing is egter nodig vir ʼn volledige geldigheidstudie. Vergelykende studies het getoon dat die liniêre isotropiese materiaalmodel die meer stabiele materiaalmodel is wat kan gebruik word om klepsuilgedrag te simuleer. Die vrye-rand lengte van die klepsuil affekteer die dinamika van die klepsuil, maar belemmer nie die werkverrigting grootliks nie. Die hemodinamiese werkverrigting van die klep verbeter met die toename in deursnee en die klepsuil-dinamika vertoon goed in ag genome die verhoogde oppervlak area en lengte. Die vele beperkings in die sagteware het die implementering van meer akkurate materiaalmodelle verhoed. Hierdie beperkings het ʼn verminderde vertroue in die resultate tot gevolg gehad. Verdere ondersoek rakende die implementering van die FSI simulasies van ʼn hartklep deur kommersieel beskikbare sagteware te gebruik, word aanbevel.
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.
The 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
Boilevin-Kayl, Ludovic. "Modeling and numerical simulation of implantable cardiovascular devices." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS039.
This 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
Gomes, Vivian Carla da Silva. "Modelo experimental de estudo da hipertensão intra-abdominal: efeitos sobre o fluxo aórtico e pressão arterial sistêmica." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/5/5132/tde-07032017-142055/.
INTRODUCTION: The intra-abdominal pressure has been shown to possess an important effect over homeostasis and might be influenced by numerous conditions. The present medical literature shows that intra-abdominal pressure values above 200 mmHg might be observed, even in physiological phenomena as coughing. Recent case reports describe the collapse of abdominal aorta due to intra-abdominal hypertension. In this study, through simulation, we measured the hazard degree to the flow through infrarenal abdominal aorta as well as to systemic arterial pressure and abdominal perfusion pressure during progressive intra-abdominal pressure increments. OBJECTIVES: To estimate, through simulation, how the intra-abdominal pressure increment would influence the hemodynamic status, compromising the systemic arterial pressure and the flow through abdominal aorta. Evaluate the validity of the abdominal perfusion pressure usage, as it is calculated today, as a reliable parameter in hemodynamic monitoring. METHODS: An artificial circulatory system enabled the simulation of the intra-abdominal pressure effects over the flow through the infrarenal abdominal aorta (represented by a silicone tube) as well as over the systemic arterial pressure. Prosthetic conduits were set inside the silicone tube (Dacron or endoprosthesis) to simulate a surgical approach over the aorta. Five experiment categories simulating clinical scenarios were defined at the study starting point: severe hypotension, slight hypotension, normotension, slight hypertension and severe hypertension. RESULTS: The data obtained along the intra-abdominal pressure increment from 10 up to 230 mmHg were analyzed considering three different specimens (silicone tube / silicone tube + Dacron / silicone tube + endoprosthesis), five experimental scenarios and seven variables of interest (upstream and downstream systolic and diastolic pressures, systolic and diastolic flow and abdominal perfusion pressure). Statistical evaluation through variance analysis showed that the intraabdominal pressure has a clear influence in all variables of interest (p < 0,001), independently of the experimental scenario or the specimen considered. The Tukey test, in the comparison of the specimens two by two, showed that the combination silicone tube + endoprosthesis had the greatest resilience to the deleterious intra-abdominal pressure effect in most part of the experimental scenarios (p = 0,05) over all the interest variables, with exception to the abdominal perfusion pressure. The abdominal perfusion pressure, calculated by the formula used in the medical literature, presented the most significant decrement along the silicone tube + endoprosthesis experiments. CONCLUSIONS: The intra-abdominal pressure has a clear influence in all variables of interest. The formula which describes the abdominal perfusion pressure calculation might not consider the dependency relationship that might exist between mean arterial pressure and the intra-abdominal pressure
Sala, Lorenzo. "Modélisation mathématique et simulation de flux sanguins oculaires et leur interactions." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAD021.
Optic 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.
The 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
Rocha, Felipe Figueredo. "Aspectos básicos da modelagem multiescala de tecidos biológicos." Laboratório Nacional de Computação Científica, 2014. https://tede.lncc.br/handle/tede/206.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)
A detailed mechanical behaviour of the arterial wall is required to gain insight on the onset and progress of some cardiovascular diseases as well as to propose adequate treatments. The classical constitutive modelling approach based purely on phenomenological laws fails in representing the micromechanical phenomena which dominates important aspects of these tissues such as remodelling and rupture. In turn, the multi-scale constitutive modelling raises as a more rational alternative that allows to consider the microscopic features and interactions of the basic unit blocks of the biological tissues such as the existence of the collagen fibres,pores, etc. In this work we review the non-linear solid mechanics fundamental concepts, the linearisation of the variational principles, numerical treatment of incompressibility constraint as well the continuum damage theory. A constitutive multi-scale theory based on the existence of Representative Volume Element in the finite strain regime is presented in a variational formulation framework, where homogenization for the displacement and deformation gradient are assumed as well the energetic coupling between scales through a extended version of the Hill-Mandel principle. In this context, a number of simulations are discussed. Finally, as corollary of the continuum mechanics framework, we derive a strategy for the damage field identification which is based on the sensibility analysis of a cost functional which takes account the displacement and energies diferences.
Sabe-se que o conhecimento do comportamento mecânico da parede arterial è fundamental para a compreensão de diversas doenças cardiovasculares bem como o planejamento adequado do tratamento destas. Contudo a modelagem da resposta constitutiva deste tecido é complexa sendo que a abordagem clássica baseada puramente em leis fenomenológicas _e insuficiente para representar fenômenos micromecânicos, os quais, ademais, dominam aspectos tais como remodelagem e ruptura. A modelagem multiescala de tecidos biológicos surge então como uma alternativa mais racional para representar a resposta constitutiva destes materiais levando-se em consideração aspectos microscópicos da organização do tecido como a existência de fibras de colágeno, poros, etc. Neste trabalho revisamos os conceitos fundamentais da mecânica dos sólidos não-linear incluindo a linearização dos princípios variacionais, bem como os aspectos básicos das teoria constitutiva em grandes deformações, passando pelo tratamento da condição de incompressibilidade e a teoria do dano contínuo. Uma teoria constitutiva multiescala baseada na homogenização em um Elemento de Volume Representativo em regime de grandes deformações é apresentada em um contexto de formulações variacionais, sendo assumida a homogeneização do campo de deslocamentos e do gradiente de deformação, além da consistência energética entre escalas baseada no princípio de Hill-Mandel. Neste contexto, diversas simulações são apresentadas e discutidas. Porém, como corolário da abordagem da mecânica do contínuo, mostramos uma estratégia para a identificação do campo de dano baseado na análise de sensibilidade de um funcional custo baseado nas diferenças de campos de deslocamentos e energia de deformação.
Zenses, 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.
Transcatheter 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
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.
Aging 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
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.
Human 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
Martins, André Augusto Carvalho. "Hemodynamic simulations in a stenosed left coronary artery - FFR quantification using a Windkessel model." Master's thesis, 2021. https://hdl.handle.net/10216/136641.
"Meshless deformable models for medical simulation applications." 2013. http://library.cuhk.edu.hk/record=b5549767.
首先,我們在這篇論文中建議把無網格流變模擬框架應用於血管手術的建模中。於非牛頓粘性流動的假設下,我們建立了血液結構的一般模型方程:以平滑粒子流體動力學實現多血粘度模型與低彈性血管壁模型。血流動力學和軟組織都可以於相同的拉格朗日粒子為基礎下模擬。在這個意義上說,通過延伸平滑粒子流體動力學的密度和動量求和不管顆粒的性質下,本論文提出了一個有效的流體 - 固體交互作用模型。該模型是特別有利於整合多種類型的介質(包括固體或液體)的。在這方面,我們進一步提出了一個與流體相關的血塊凝集溶解模型,可以適用於許多不同種類的醫學模擬:例如血栓栓塞。
其次,本論文亦提出了如何基於粒子的血液建模框架的前提下,擴展到大變形的軟組織互動。我們是以耦合雙向階段性質量 - 彈簧系統與固體顆粒,去代替無網格粒子固體的建模,用以維持真正人體組織的高保真度,此方法可以實現類似軟組織的皮膚或真皮的交互式模擬。而耦合血顆粒與平滑粒子方面,則由一個聰明的碰撞模塊處理,使得利用模擬皮膚表面之上,可以模擬出真實的表皮出血現象。該模型的動態計算進一步以物理學處理單元加速;而渲染的模型則是通過一個強大的圖形處理單元為基礎的立方體運行(marching cubes)的方法來實現。該模型已應用於全身血液管理培訓中。
In this thesis, we propose particle-based rheological modeling frameworks for blood-vessel and blood-wound interaction in medical simulation applications. The effect of blood rheology has been simulated through a smoothed particle hydrodynamics (SPH) formulation of non-Newtonian flow. By modeling the vessel wall structure as virtual particles, a pure Lagrange particle formulation for fluid-structure interaction (FSI) is proposed for modeling the blood-vessel or blood-device interaction. Our proposed framework synthesizes common vascular complication sites such as stenosis and aneurysm based on purely mesh-less approach. For larger deformation situations happened in surgical sites such as open wound, we adopt a mass-spring system to interact with the blood particles; the blood-wound interaction framework can be applied to several open surgery simulations such as orthopedics or endoscopy-based interventions. Input of the data can be obtained from either common medical modalities like computed tomographic angiography (CTA), magnetic resonance angiography (MRA) or processing mesh-based data. A thrombus (clot) formation-dissolution model is also integrated into this fluid-solid interaction framework. Results have demonstrated the feasibility of employing our proposed particle framework in simulating blood-vessel interaction in the clotting process which is essential to vascular procedure simulations. Having benefited from the elegant formulation of Lagrangian particle interaction; the simulation can be maintained at interactive frame-rates.
In this thesis, first, a meshless rheological modeling framework for medical simulation of vascular procedures is proposed. Instead of assuming a Newtonian non-viscous flow, we have built our model based on the general constitutive equation of blood. The multi-regime of viscosity in blood model with a hypoelastic model of vessel wall has been realized under a SPH formulation. The hemodynamic and the soft tissue can all be simulated under the same Lagrangian particle-based formulation. In this sense, an efficient formulation of fluid-solid interaction is proposed through extending SPH summations of density and momentum regardless the nature of particles. This model is particularly beneficial to the integration of multiple types of media (including solids or fluids). With this regards, we further propose a flow related clot aggregation-dissolution model which can be applicable to many different kinds of medical simulation e.g. thrombo-embolization.
Second, the proposed particle-based blood modeling framework has been extended to interact with large deformation of soft tissue. Instead of modeling the solid as meshless particles, a bi-phasic mass-spring system is coupled with solid particles so that an interactive simulation of skin or dermis like soft tissue can be realized with high fidelity to real human tissue. To couple with the SPH formulation of blood particles, a smart collision handling module is exploited so that a realistic bleeding simulation on top of the skin surface can be created. The dynamic computation of this model is further accelerated by the physics processing unit; while the rendering of the model is realized through a robust graphics processing unit based marching cube approach. The proposed model has been applied to provide general blood management training.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Chui, Yim Pan.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2013.
Includes bibliographical references (leaves 98-113).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts also in Chinese.
Abstract --- p.ii
Chapter 1 --- Introduction --- p.1
Chapter 2 --- Related works on physically based fluid-structure models --- p.7
Chapter 2.1 --- Eulerian grid-based methods --- p.8
Chapter 2.2 --- Lagrangian grid-based methods --- p.9
Chapter 2.3 --- Lagrangian meshfree methods --- p.11
Chapter 2.4 --- Fluid-structure interaction (FSI) --- p.12
Chapter 2.5 --- Endovascular simulation --- p.14
Chapter 2.6 --- Overview of Our Model --- p.15
Chapter 3 --- Meshless blood-clot interaction --- p.16
Chapter 3.1 --- Basic equations of fluid dynamics --- p.17
Chapter 3.2 --- SPH basics --- p.18
Chapter 3.3 --- SPH Rheological hemodynamics of blood --- p.20
Chapter 3.4 --- SPH modeling of the hypoelastic vessel --- p.26
Chapter 3.5 --- Fluid-solid interaction model --- p.28
Chapter 3.6 --- Flow-related clot aggregation-dissolution model --- p.33
Chapter 3.7 --- Time integration --- p.36
Chapter 3.8 --- Hardware-friendly formulation --- p.37
Chapter 3.9 --- Results --- p.39
Chapter 3.9.1 --- Classical Dam-break problem --- p.41
Chapter 3.9.2 --- Poiseuille flow --- p.43
Chapter 3.9.3 --- Couette flow --- p.45
Chapter 3.9.4 --- Mechanical model with material strength --- p.47
Chapter 3.9.5 --- Hemoelastic feedback system --- p.49
Chapter 3.9.6 --- Clotting in a stenosed vessel --- p.52
Chapter 3.9.7 --- Timing results --- p.53
Chapter 4 --- Meshless modeling of thrombo-embolization --- p.55
Chapter 4.1 --- Modeling framework for thrombus formation within blood vessel . --- p.60
Chapter 4.2 --- Geometric Modeling and Flow Simulation --- p.61
Chapter 4.2.1 --- Data processing on vascular data --- p.61
Chapter 4.2.2 --- Blood-Vessel particle distribution --- p.62
Chapter 4.2.3 --- Blood-structure Interaction --- p.65
Chapter 4.3 --- Visualization and Thrombosis Simulation --- p.66
Chapter 4.3.1 --- Flow Visualization --- p.66
Chapter 4.3.2 --- Thromb-Embolization Simulation --- p.68
Chapter 4.4 --- Conclusion and discussion --- p.72
Chapter 5 --- Lagrangian modeling framework for bleeding simulation --- p.76
Chapter 5.1 --- SPH-based bleeding model --- p.78
Chapter 5.2 --- Biphasic Soft-tissue deformation --- p.79
Chapter 5.3 --- Interaction between blood and soft tissue --- p.83
Chapter 5.4 --- Integrated training for blood management --- p.87
Chapter 6 --- Discussion and Conclusion --- p.93
Bibliography --- p.98
Sin-SyuanCai and 蔡欣璇. "Hemodynamic Simulation of Total Cavopulmonary Connection Flow Using a Hybrid Circulation Model." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/84690047399964611662.
國立成功大學
航空太空工程學系
104
Hemodynamics improvement in patients with single ventricle heart defects could be accomplished by palliative surgical procedure. The purpose of the final stage surgery in total cavopulmonary connection is to reconstruct the arteriovenous shunt, as well as to separating systemic and pulmonary circulation and reduce ventricular loading. However, the increase in venous return pressure or decrease in left ventricular preload are common in these physiological circulation reconstruction, and ultimately lead to protein losing enteropathy, hepatic congestion, thromboembolism and diminished exercise capacity. It is important to optimize the TCPC flow to mitigate the abovementioned complications. Computational Fluid Dynamics has been adopted as the major analysis tool, in which both flow model and boundary condition specification are crucial. The present research proposed a hybrid circulation simulation model consisting of a continuous three-dimensional flow model and a lumped-parameter model. Three-dimensional flow field simulation uses Ansys Fluent with implicit SIMPLE algorithms in conjunction with a user-defined function to combine lumped-parameter model as the terminal boundary conditions. The lumped-parameter model is solved based on explicit fourth-order Runge-Kutta method for time stepping. A special iterative procedure connecting the Fluent solver and the lumped-parameter system is developed. The hybrid circulation model in three-dimensional hemodynamic simulation was successfully validated. The simulation results show that, for the studied cases, there is no significant difference in power loss for TCPC flow field due to velocity of venous return is too small.
Hu, Eric Haujuan, and 胡浩鈞. "A Numerical Study on Parallel Hemodynamics Simulation Using Non-Newtonian Model." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/42290077774259858893.
國立中央大學
數學系
103
Numerical simulation of blood flow in the arteries becomes an invaluable tools to help both of the physicians to plan the surgery procedure to reduce the risk of surgery and the researchers to understand the cardiovascular diseases. To ease the numerical difficulties of blood flow simulation, blood is often assumed to be Newtonian fluid as the first approximation. However, the shear thinning effect is significant in large arteries due to the dramatic change of the shear stress during a cardiac cycle and the non-homogeneous properties of blood. Moreover, the recirculation happens frequently in the low shear rate region. To compute accurately the wall shear stress that provides more useful information to predict the formation of intimal hyperplasia, it is necessary to take the rheological effect of blood flows in to account. In this study, the non-Newtonian blood flows in different complexity of artery were numerically investigated by using 3D fully parallel incompressible fluid solver. Our fluid solver is developed based on generalized Newtonian fluid model, where the viscosity is the function of rate of strain tensor. More specifically, the more commonly-used model for blood flow simulation, the Carreau-Yasuda model, compared with Newtonian model are reported, including the investigation how the wall shear stress distribution and the streamlines and pressure distribution depend on different physiological conditions and arterial geometries.
Lesage, Susan Jane. "Central and peripheral hemodynamic responses to a tilt table simulation of -/+ Gz transitions." 1999. http://wwwlib.umi.com/cr/yorku/fullcit?pMQ39205.
Typescript. Includes bibliographical references (leaves 77-83). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ39205.
Souza, Andrews Victor Almeida de. "Hemodynamic study in a real intracranial aneurysm: an in vitro and in silico approach." Master's thesis, 2016. http://hdl.handle.net/10198/22681.
Intracranial aneurysm (IA) is a cerebrovascular disease with high rates of mortality and morbidity when it ruptures. It is known that changes in the intra-aneurysmal hemodynamic load play a significant factor in the development and rupture of IA. However, these factors are not fully understood. In this sense, the main objective of this work is to study the hemodynamic behavior during the blood analogues flow inside an AI and to determine its influence on the evolution of this pathology. To this end, experimental and numerical studies were carried out, using a real AI model obtained using computerized angiography. In the experimental approach, it was necessary, in the initial phase, to develop and manufacture biomodels from medical images of real aneurysms. Two techniques were used to manufacture the biomodels: rapid prototyping and gravity casting. The materials used to obtain the biomodels were of low cost. After manufacture, the biomodels were compared to each other for their transparency and final structure and proved to be suitable for testing flow visualizations. Numerical studies were performed with the aid of the Ansys Fluent software, using computational fluid dynamics (CFD), using the finite volume method. Subsequently, flow tests were performed experimentally and numerically using flow rates calculated from the velocity curve of a patient's doppler test. The experimental and numerical tests, in steady-state, made it possible to visualize the three-dimensional behavior of the flow inside the aneurysm, identifying the vortex zones created throughout the cardiac cycle. Correlating the results obtained in the two analyzes, it was possible to identify that the areas of vortexes are characterized by low speed and with increasing the fluid flow, the vortexes are positioned closer to the wall. These characteristics are associated with the rupture of an intracranial aneurysm. There was also a good qualitative correlation between numerical and experimental results.
O aneurisma intracraniano (AI) é uma patologia cerebrovascular com altas taxas de mortalidade e morbidade quando se rompe. Sabe-se que alterações na carga hemodinâmica intra-aneurismática exerce um fator significativo no desenvolvimento e ruptura de AI, porém, esses fatores não estão totalmente compreendidos. Nesse sentido, o objetivo principal deste trabalho é o de estudar o comportamento hemodinâmico durante o escoamento de fluidos análogos do sangue no interior de um AI e determinar a sua influência na evolução da patologia. Para tal, foram realizados estudos experimentais e numéricos, utilizando um modelo de AI real obtido por meio de uma angiografia computadorizada. Na abordagem experimental foi necessário, na fase inicial, desenvolver e fabricar biomodelos a partir de imagens médicas de um aneurisma real. No fabrico dos biomodelos foram utilizadas duas técnicas: a prototipagem rápida e o vazamento por gravidade. Os materiais utilizados para a obtenção dos biomodelos foram de baixo custo. Após a fabricação, os biomodelos foram comparados entre si quanto à sua transparência e estrutura final e verificou-se serem adequados para testes de visualizações do fluxo. Os estudos numéricos foram realizados com recurso ao software Ansys Fluent, utilizando a dinâmica dos fluidos computacional (CFD), através do método dos volumes finitos. Posteriormente, foram realizados testes de escoamento experimentais e numéricos, utilizando caudais determinados a partir da curva de velocidades do ensaio doppler de um paciente. Os testes experimentais e numéricos, em regime permanente, possibilitaram a visualização do comportamento tridimensional do fluxo no interior do aneurisma, identificando as zonas de vórtices criadas ao longo do ciclo cardíaco. Correlacionando os resultados obtidos nas duas análises, foi possível identificar que as áreas de vórtices são caracterizadas por uma baixa velocidade e com o aumento do caudal os vórtices posicionam-se mais próximos da parede. Essas características apresentadas estão associadas com a ruptura de aneurisma intracraniano. Verificou-se, também, uma boa correlação qualitativa entre os resultados numéricos e experimentais.
蔡嘉瑋. "Numerical Simulation on Structure Stress and Hemodynamics of Intracranial Fusiform Aneurysms with Rigid and Flexible Walls." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/57727033583695863842.
Herdade, Ana Santos Silva 1979. "Microcirculation and inflammation in a numerical simulation approach." Doctoral thesis, 2016. http://hdl.handle.net/10451/42628.
蔡宗翰. "Study on the Intra-Aneurysmal Hemodynamics in the Internal Carotid Artery Using Image Reconstruction Method, Numerical Simulation, and Flow Visualization." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/53207416776620578065.
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.
Deep, Debanjan. "A study of blood flow in normal and dilated aorta." Thesis, 2013. http://hdl.handle.net/1805/4440.
Atherosclerotic lesions of human beings are common diagnosed in regions of arte- rial branching and curvature. The prevalence of atherosclerosis is usually associated with hardening and ballooning of aortic wall surfaces because of narrowing of flow path by the deposition of fatty materials, platelets and influx of plasma through in- timal wall of Aorta. High Wall Shear Stress (WSS) is proved to be the main cause behind all these aortic diseases by physicians and researchers. Due to the fact that the atherosclerotic regions are associated with complex blood flow patterns, it has believed that hemodynamics and fluid-structure interaction play important roles in regulating atherogenesis. As one of the most complex flow situations found in cardio- vascular system due to the strong curvature effects, irregular geometry, tapering and branching, and twisting, theoretical prediction and in vivo quantitative experimental data regarding to the complex blood flow dynamics are substantial paucity. In recent years, computational fluid dynamics (CFD) has emerged as a popular research tool to study the characteristics of aortic flow and aim to enhance the understanding of the underlying physics behind arteriosclerosis. In this research, we study the hemo- dynamics and flow-vessel interaction in patient specific normal (healthy) and dilated (diseased) aortas using Ansys-Fluent and Ansys-Workbench. The computation con- sists of three parts: segmentation of arterial geometry for the CFD simulation from computed tomography (CT) scanning data using MIMICS; finite volume simulation of hemodynamics of steady and pulsatile flow using Ansys-Fluent; an attempt to perform the Fluid Structure Simulation of the normal aorta using Ansys-Workbench. Instead of neglecting the branching or smoothing out the wall for simplification as a lot of similar computation in literature, we use the exact aortic geometry. Segmen- tation from real time CT images from two patients, one young and another old to represent healthy and diseased aorta respectively, is on MIMICS. The MIMICS seg- mentation operation includes: first cropping the required part of aorta from CT dicom data of the whole chest, masking of the aorta from coronal, axial and saggital views of the same to extract the exact 3D geometry of the aorta. Next step was to perform surface improvement using MIMICS 3-matic module to repair for holes, noise shells and overlapping triangles to create a good quality surface of the geometry. A hexahe- dral volume mesh was created in T-Grid. Since T-grid cannot recognize the geometry format created by MIMICS 3-matic; the required step geometry file was created in Pro-Engineer. After the meshing operation is performed, the mesh is exported to Ansys Fluent to perform the required fluid simulation imposing adequate boundary conditions accordingly. Two types of study are performed for hemodynamics. First is a steady flow driven by specified parabolic velocity at inlet. We captured the flow feature such as skewness of velocity around the aortic arch regions and vortices pairs, which are in good agreement with open data in literature. Second is a pulsatile flow. Two pulsatile velocity profiles are imposed at the inlet of healthy and diseased aorta respectively. The pulsatile analysis was accomplished for peak systolic, mid systolic and diastolic phase of the entire cardiac cycle. During peak systole and mid-systole, high WSS was found at the aortic branch roots and arch regions and diastole resulted in flow reversals and low WSS values due to small aortic inflow. In brief, areas of sudden geometry change, i.e. the branch roots and irregular surfaces of the geom- etry experience more WSS. Also it was found that dilated aorta has more sporadic nature of WSS in different regions than normal aorta which displays a more uniform WSS distribution all over the aorta surface. Fluid-Structure Interaction simulation is performed on Ansys-WorkBench through the coupling of fluid dynamics and solid mechanics. Focus is on the maximum displacement and equivalent stress to find out the future failure regions for the peak velocity of the cardiac cycle.