Escoamento pulsado do sangue na região das ramificações renais da artéria aorta abdominal: estudo de caso
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2017-11-17
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O conhecimento das relações entre os valores de alguns índices hemodinâmicos e o aparecimento de lesões nas paredes da artéria aorta é importante para o desenvolvimento de ferramentas que permitam diagnosticar atempadamente doenças que frequentemente surgem nestas zonas. Nesta dissertação apresenta-se um estudo hemodinâmico numa porção da artéria aorta que engloba a bifurcação nas artérias renais e a artéria abdominal infrarrenal. O estudo foi realizado recorrendo a simulações computacionais do escoamento sanguíneo em dois modelos tridimensionais da porção da artéria em estudo, obtidos por dois processos de reconstrução diferentes. Os modelos tridimensionais foram reconstruídos a partir de imagens médicas bidimensionais obtidas por tomografia computadorizada. Foram realizadas duas simulações em cada um dos modelos, numa das simulações assume-se que a viscosidade do sangue apresenta um comportamento newtoniano descrito pelo modelo de Lee & Steinman, na outra simulação a viscosidade do sangue apresenta um comportamento não newtoniano descrito pelo modelo de Carreau. Analisam-se os resultados de um conjunto de índices hemodinâmicos baseados nas tensões de corte desenvolvidas nas paredes da artéria. Verificou-se que as diferenças geométricas existentes entre os dois modelos tridimensionais reconstruídos podem induzir alterações significativas nas variáveis hemodinâmicas estudadas. Investigou-se também a influência das geometrias nos efeitos não newtonianos para as condições do presente estudo. As soluções obtidas permitiram identificar que as zonas próximas da bifurcação da artéria renal direita são mais suscetíveis ao aparecimento de algumas doenças cardiovasculares que tipicamente surgem nestas zonas. É possível constatar que os índices OSI e RRT são os mais sensíveis às diferenças geométricas resultantes do processo de reconstrução das artérias. Estes índices hemodinâmicos são também os mais suscetíveis aos efeitos não newtonianos.
The knowledge of the relationship between the values of some hemodynamic indexes and the appearance of lesions on the walls of the aorta artery is important in order to develop tools that allow early diagnosis of diseases that frequently arise in these areas. This dissertation presents a hemodynamic study in a portion of the aorta artery that includes the bifurcation in the renal arteries and the infrarenal abdominal artery. The study was carried out using computational simulations of the blood flow in two three-dimensional models of the portion of the artery under study, obtained by two different reconstruction processes. The threedimensional models were reconstructed from two-dimensional medical images obtained by computed tomography. Two simulations were performed in each of the models, in one of the simulations, it is assumed that the blood viscosity presents a Newtonian behavior described by the model of Lee & Steinman, in the other simulation the blood viscosity presents a nonNewtonian behavior described by the Carreau model. The results of a set of hemodynamic indexes based on the wall shear stress developed on the walls of the artery are analyzed. It was verified that the geometric differences between the two reconstructed three-dimensional models can induce significant changes in the studied hemodynamic variables. The influence of the geometries on the non-Newtonian effects was also investigated for the conditions of the present study. The obtained solutions allowed to identify that the zones near the bifurcation of the right renal artery are more susceptible to the appearance of some cardiovascular diseases that typically appear in these zones. It is possible to verify that the OSI and RRT indexes are the most sensitive to the geometric differences resulting from the reconstruction processes of the arteries. These hemodynamic indexes are also the most susceptible to the non-Newtonian effects.
The knowledge of the relationship between the values of some hemodynamic indexes and the appearance of lesions on the walls of the aorta artery is important in order to develop tools that allow early diagnosis of diseases that frequently arise in these areas. This dissertation presents a hemodynamic study in a portion of the aorta artery that includes the bifurcation in the renal arteries and the infrarenal abdominal artery. The study was carried out using computational simulations of the blood flow in two three-dimensional models of the portion of the artery under study, obtained by two different reconstruction processes. The threedimensional models were reconstructed from two-dimensional medical images obtained by computed tomography. Two simulations were performed in each of the models, in one of the simulations, it is assumed that the blood viscosity presents a Newtonian behavior described by the model of Lee & Steinman, in the other simulation the blood viscosity presents a nonNewtonian behavior described by the Carreau model. The results of a set of hemodynamic indexes based on the wall shear stress developed on the walls of the artery are analyzed. It was verified that the geometric differences between the two reconstructed three-dimensional models can induce significant changes in the studied hemodynamic variables. The influence of the geometries on the non-Newtonian effects was also investigated for the conditions of the present study. The obtained solutions allowed to identify that the zones near the bifurcation of the right renal artery are more susceptible to the appearance of some cardiovascular diseases that typically appear in these zones. It is possible to verify that the OSI and RRT indexes are the most sensitive to the geometric differences resulting from the reconstruction processes of the arteries. These hemodynamic indexes are also the most susceptible to the non-Newtonian effects.
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hemodinâmica , artéria aorta abdominal , artérias renais , índices hemodinâmicos , modelos de viscosidade , processos de reconstrução