Hemodinâmica da bifurcação da artéria aorta abdominal: análise de índices hemodinâmicos
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2017-09-13
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O conhecimento do comportamento da hemodinâmica na zona da bifurcação da artéria aorta abdominal (AAA) é de elevada importância para o melhor entendimento e diagnóstico precoce de algumas doenças cardiovasculares características da artéria aorta.
O trabalho desenvolvido foca-se no estudo de caso da hemodinâmica da artéria aorta abdominal, tendo como base um modelo geométrico realista 3D da bifurcação da artéria aorta abdominal reconstruído a partir de imagens médicas 2D de um paciente real com problemas associados a uma elevada viscosidade sanguínea.
Os perfis da velocidade do batimento cardíaco do paciente, na aorta abdominal e nas ilíacas, foram obtidos com recurso a imagens de ultrassonografia Doppler. O perfil do escoamento sanguíneo na aorta abdominal foi usado como condição fronteira, nas simulações computacionais, para a entrada do sangue na bifurcação da artéria aorta abdominal. Os resultados das simulações computacionais permitiram a análise de algumas variáveis hemodinâmicas tais como a distribuição da velocidade, da pressão, da taxa de deformação e das tensões de corte nas paredes da artéria. Foram analisados alguns índices hemodinâmicos e relacionados entre si, bem como, com o risco de desenvolvimento de aterosclerose, trombose e eventual degradação do endotélio. Foi ainda feita uma análise comparativa entre as soluções numéricas obtidas para duas condições fronteira na entrada diferentes; uma com o perfil de velocidade parabólico e outra com perfil constante.
Nesta investigação, o escoamento sanguíneo durante um ciclo cardíaco foi considerado em regime laminar, sendo utilizado o modelo newtoniano da viscosidade do sangue proposto por Lee e Steinman (2007). As equações de Navier-Stokes que governam o escoamento, durante um ciclo cardíaco, foram resolvidas numericamente pelo método dos volumes finitos. As soluções obtidas para os índices hemodinâmicos estudados permitiram identificar zonas da artéria com maior probabilidade de desenvolverem doenças cardiovasculares.
The knowledge of the hemodynamic behaviour of the abdominal aorta artery bifurcation is of great importance for the better understanding and early diagnosis of some frequent cardiovascular diseases of the aorta artery. The work developed focuses on the case study of the abdominal aorta artery hemodynamic, based on a realistic 3D geometric model of the abdominal aorta artery bifurcation reconstructed from 2D medical images of a real patient with problems associated with a high blood viscosity. The velocity profiles of the patient's heart beat, in the abdominal aorta and iliacs, were obtained using Doppler ultrasonography images. The blood flow profile in the abdominal aorta was used, in the computational simulations, as inlet boundary condition of blood in the bifurcation of the abdominal aorta. The results of the computational simulations allowed the analysis of some hemodynamic variables such as velocity, pressure, strain rate and wall shear stress. Some hemodynamic indices were analysed and related, as well as the risk of developing atherosclerosis, thrombosis and eventual endothelium degradation. A comparative analysis was also performed between the numerical solutions obtained for two different inlet conditions; one with a parabolic velocity profile and the other with a constant velocity profile. In this investigation, the blood flow during a cardiac cycle was considered in laminar regime, using the newtonian blood viscosity model proposed by Lee and Steinman (2007). The Navier-Stokes equations governing flow, corresponding to a cardiac cycle, were solved numerically by the finite volume method. The solutions obtained for the hemodynamic indices allowed to identify the artery zones most likely to develop cardiovascular diseases.
The knowledge of the hemodynamic behaviour of the abdominal aorta artery bifurcation is of great importance for the better understanding and early diagnosis of some frequent cardiovascular diseases of the aorta artery. The work developed focuses on the case study of the abdominal aorta artery hemodynamic, based on a realistic 3D geometric model of the abdominal aorta artery bifurcation reconstructed from 2D medical images of a real patient with problems associated with a high blood viscosity. The velocity profiles of the patient's heart beat, in the abdominal aorta and iliacs, were obtained using Doppler ultrasonography images. The blood flow profile in the abdominal aorta was used, in the computational simulations, as inlet boundary condition of blood in the bifurcation of the abdominal aorta. The results of the computational simulations allowed the analysis of some hemodynamic variables such as velocity, pressure, strain rate and wall shear stress. Some hemodynamic indices were analysed and related, as well as the risk of developing atherosclerosis, thrombosis and eventual endothelium degradation. A comparative analysis was also performed between the numerical solutions obtained for two different inlet conditions; one with a parabolic velocity profile and the other with a constant velocity profile. In this investigation, the blood flow during a cardiac cycle was considered in laminar regime, using the newtonian blood viscosity model proposed by Lee and Steinman (2007). The Navier-Stokes equations governing flow, corresponding to a cardiac cycle, were solved numerically by the finite volume method. The solutions obtained for the hemodynamic indices allowed to identify the artery zones most likely to develop cardiovascular diseases.
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Dissertação de Mestrado em Engenharia Biomédica
Palavras-chave
Hemodinâmica , Artéria aorta abdominal , Bifurcação , Fluxo pulsado , Tensões de corte nas paredes