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Stress-Strain Analysis of Aortic Aneurysms
Polzer, Stanislav ; Holeček, Miroslav (oponent) ; Horný, Lukáš (oponent) ; Burša, Jiří (vedoucí práce)
This thesis deals with abdominal aortic aneurysms and the possibility of using finite element method in assessment of their rupture risk. First part of the thesis is dedicated to an introduction into the problem, description of human cardiovascular system where the abdominal aorta, its anatomy, physiology and pathology is emphasized. There Processes leading to formationing of abdominal aortic aneurysms are also discussed. Risk factors contributing to creation of aneurysms are discussed next. Finally, an analysis of current clinical criteria which determine rupture risk of an abdominal aortic aneurysm is presented and compared with the new maximum stress criterion being currently in development. Main part of the thesis deals with the identification of relevant factors which affect stress and deformation of aneurysmal wall. This is connected with proposals of new approaches leading to predicting the rupture risk more accurately by using finite element stress-strain analysis. The impact of geometry is analyzed first with the conclusion that patient-specific geometry is a crucial input in the computational model. Therefore its routine reconstruction has been managed. Attention is then paid to the branching arteries which were neglected so far although they cause a stress concentration in arterial wall. The necessity of knowing the unloaded geometry of aneurysm is then emphasized. Therefore a macro has been written in order to be able to find the unloaded geometry for any patient-specific geometry of aneurysm. Mechanical properties of both aneurysmal wall and intraluminal thrombus were also experimentally tested and their results were fitted by an isotropic material model. The effect of the material model itself has been also investigated by comparing whole stress fields of several aneurysms. It has been shown that different models predict completely different stresses due to different stress gradients in the aneurysmal wall. The necessity of known collagen fiber distribution in arterial wall is also emphasized. A special program is then presented enabling us to obtain this information. Effect of intraluminal thrombus on the computed wall stress is analyzed in two perspectives. First the effect of its failure on wall stress is shown and also the impact of its poroelastic structure is analyzed. Finally the residual stresses were identified as an important factor influencing the computed wall stress in aneurysmal wall and they were included into patient-specific finite element analysis of aneurysms. Further possible regions of investigation are mentioned as the last part of the thesis.
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Stress-Strain Analysis of Aortic Aneurysms
Polzer, Stanislav ; Holeček, Miroslav (oponent) ; Horný, Lukáš (oponent) ; Burša, Jiří (vedoucí práce)
This thesis deals with abdominal aortic aneurysms and the possibility of using finite element method in assessment of their rupture risk. First part of the thesis is dedicated to an introduction into the problem, description of human cardiovascular system where the abdominal aorta, its anatomy, physiology and pathology is emphasized. There Processes leading to formationing of abdominal aortic aneurysms are also discussed. Risk factors contributing to creation of aneurysms are discussed next. Finally, an analysis of current clinical criteria which determine rupture risk of an abdominal aortic aneurysm is presented and compared with the new maximum stress criterion being currently in development. Main part of the thesis deals with the identification of relevant factors which affect stress and deformation of aneurysmal wall. This is connected with proposals of new approaches leading to predicting the rupture risk more accurately by using finite element stress-strain analysis. The impact of geometry is analyzed first with the conclusion that patient-specific geometry is a crucial input in the computational model. Therefore its routine reconstruction has been managed. Attention is then paid to the branching arteries which were neglected so far although they cause a stress concentration in arterial wall. The necessity of knowing the unloaded geometry of aneurysm is then emphasized. Therefore a macro has been written in order to be able to find the unloaded geometry for any patient-specific geometry of aneurysm. Mechanical properties of both aneurysmal wall and intraluminal thrombus were also experimentally tested and their results were fitted by an isotropic material model. The effect of the material model itself has been also investigated by comparing whole stress fields of several aneurysms. It has been shown that different models predict completely different stresses due to different stress gradients in the aneurysmal wall. The necessity of known collagen fiber distribution in arterial wall is also emphasized. A special program is then presented enabling us to obtain this information. Effect of intraluminal thrombus on the computed wall stress is analyzed in two perspectives. First the effect of its failure on wall stress is shown and also the impact of its poroelastic structure is analyzed. Finally the residual stresses were identified as an important factor influencing the computed wall stress in aneurysmal wall and they were included into patient-specific finite element analysis of aneurysms. Further possible regions of investigation are mentioned as the last part of the thesis.
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Stress-strain analysis of aortic aneurysms
Polzer, Stanislav ; Burša, Jiří (vedoucí práce)
This thesis deals with abdominal aortic aneurysms and the possibility of using finite element method in assessment of their rupture risk. First part of the thesis is dedicated to an introduction into the problem, description of human cardiovascular system where the abdominal aorta, its anatomy, physiology and pathology is emphasized. There Processes leading to formationing of abdominal aortic aneurysms are also discussed. Risk factors contributing to creation of aneurysms are discussed next. Finally, an analysis of current clinical criteria which determine rupture risk of an abdominal aortic aneurysm is presented and compared with the new maximum stress criterion being currently in development. Main part of the thesis deals with the identification of relevant factors which affect stress and deformation of aneurysmal wall. This is connected with proposals of new approaches leading to predicting the rupture risk more accurately by using finite element stress-strain analysis. The impact of geometry is analyzed first with the conclusion that patient-specific geometry is a crucial input in the computational model. Therefore its routine reconstruction has been managed. Attention is then paid to the branching arteries which were neglected so far although they cause a stress concentration in arterial wall. The necessity of knowing the unloaded geometry of aneurysm is then emphasized. Therefore a macro has been written in order to be able to find the unloaded geometry for any patient-specific geometry of aneurysm. Mechanical properties of both aneurysmal wall and intraluminal thrombus were also experimentally tested and their results were fitted by an isotropic material model. The effect of the material model itself has been also investigated by comparing whole stress fields of several aneurysms. It has been shown that different models predict completely different stresses due to different stress gradients in the aneurysmal wall. The necessity of known collagen fiber distribution in arterial wall is also emphasized. A special program is then presented enabling us to obtain this information. Effect of intraluminal thrombus on the computed wall stress is analyzed in two perspectives. First the effect of its failure on wall stress is shown and also the impact of its poroelastic structure is analyzed. Finally the residual stresses were identified as an important factor influencing the computed wall stress in aneurysmal wall and they were included into patient-specific finite element analysis of aneurysms. Further possible regions of investigation are mentioned as the last part of the thesis.
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