Abdominal aortic aneurysms are common and responsible for many deaths. They are treated increasingly by EndoVascular Aneurysm Repair (EVAR) rather than conventional surgery. Approximately 25% of EVAR patients require re-intervention to prevent aneurysm enlargement which can rupture despite previous repair. All EVAR patients undergo life-long surveillance for complications such as stent-graft migration or endoleak. Computed Tomography (CT) has been the ‘gold-standard’ for surveillance accounting for 65% of EVAR costs, and exposes patients to cumulative radiation and nephrotoxic contrast. Duplex Ultrasound Scanning (DUS) has been proposed as an alternative for surveillance with lesser cost and patient risk. However, clinical studies have reported varying results. The addition of microbubble contrast significantly improves endoleak detection rates, making it comparable with CT. The physical properties that affect endoleak detection with DUS have not been determined. It is also unknown specifically which endoleaks’ detection are improved by Contrast Enhanced Aortic Duplex UltraSound Scanning (CEADUSS). To investigate the physical properties of endoleaks, I constructed an EVAR phantom model with a simulated endoleak of variable velocity (fast/slow), position (near/far) and plane (anterior/lateral/posterior). Preliminary studies investigated the behavior of microbubble contrast in the phantom system, and then laboratory experiments tested subjects over 36 variable endoleaks using DUS and CEADUSS. These laboratory experiments were translated clinically with a pilot study of CEADUSS in 10 patients with endoleaks on CT not detected by DUS, undefined endoleak type or origin, or a sac enlargement with no endoleak present. My experiments reveal an insight into factors influencing ultrasound endoleak detection. With this knowledge, the use of these modalities for surveillance protocols can be increased, reducing current CT burden, radiation and nephrotoxic contrast exposure, and overall EVAR cost. Clinical assessment of an endoleak, specifically noting physical characteristics (plane, position and velocity) will improve detection and surveillance.

Aneurismas são dilatações permanentes iguais ou superiores a 50% do diâmetro original de uma artéria ou do diâmetro proximal da mesma, de acordo com consenso publicado pela Sociedade de Cirurgia Vascular da América do Norte e Sociedade Internacional de Cirurgia Cardiovascular em 1991 (Vliet e Boll, 1997). Aneurisma de aorta é uma doença vascular que afeta mais de 5% da população masculina com mais de 55 anos de idade (How et al., 2005). Desde 1991 um novo método vem sendo utilizado como tratamento deste quadro clínico. Este novo método é considerado menos invasivo e com menor comorbidade, uma vez que se trata da instalação de uma endoprótese por meio de catéter através da artéria femoral. Neste trabalho, será verificado o escoamento através de três aneurismas de aorta abdominal (AAA) e das endopróteses indicadas para o tratamento de cada um dos aneurismas. Foram feitas simulações computacionais afim de se obter as pressões, as velocidades do escoamento sanguíneo e as tensões de cisalhamento na parede das geometrias, usando pulsos de pressão e velocidade fisiológico de um individuo adulto, normotenso, em repouso. No modelo de escoamento simulado, foi adotado o sangue como fluido Newtoniano, incompressível e homogêneo. Foi usado um modelo de turbulência K-, com interpolador upwind de 2ª ordem e tratamento de parede nas geometrias, para que se fosse possível obter resultados satisfatórios (das camadas próximas à parede, e de todos os vórtices). Os resultados obtidos no trabalho foram satisfatórios, uma vez que eles expressaram de forma realista o comportamento do escoamento sanguíneo pelos aneurismas e endopróteses. Foi possível justificar com esse trabalho a instalação de endopróteses em pacientes, quando necessário, com o objetivo de diminuir significativamente a degradação do vaso, causando a ruptura do aneurisma. / Aneurisms are permanently dilatation higher than 50% of the original diameter of an artery or of the proximal diameter of them, according to the published consensus of the Vascular Surgery Society of North America and International Society of Cardiovascular Surgery on 1991 (Vliet and Boll, 1997). Aortas Aneurism is a vascular disease that affects more than 5% of the male population, with more than 55 years old (How et al, 2005). Since 1991, a new method is used in the treatment of these diseases. This new method is less invasive and has less comorbidity. This method is provided by the installation of an endoprosthesis through the catheter through the femoral artery. In this work, the flow will be verified through three abdominal aortic aneurysms (AAA) and the endoprosthesis indicated for the treatment of each of the aneurysms. Computational simulations were made in order to obtain the pressures, velocities of the blood flow and the shear stresses on the wall of geometries, using a pulse pressure and velocity of an individual physiological adult normotensive at rest. For the fluid simulations, it was adopted the blood as Newtonian fluid, incompressible and homogeneous. In simulations, it was used a K- model of turbulence, with 2nd order upwind interpolator and wall geometry treatment in order to obtain satisfied results (on the layers near the walls, and all the vortices). The results obtained in this work were satisfied, once they expressed the realistic behavior of the blood flow through the aneurysm and the endoprosthesis. It was possible to justify with this work the installation of an endoprosthesis inside patients, when it is necessary, in order to decrease significantly the vessels degradation, causing the aneurysm rupture.

Aneurismas são dilatações permanentes iguais ou superiores a 50% do diâmetro original de uma artéria ou do diâmetro proximal da mesma, de acordo com consenso publicado pela Sociedade de Cirurgia Vascular da América do Norte e Sociedade Internacional de Cirurgia Cardiovascular em 1991 (Vliet e Boll, 1997). Aneurisma de aorta é uma doença vascular que afeta mais de 5% da população masculina com mais de 55 anos de idade (How et al., 2005). Desde 1991 um novo método vem sendo utilizado como tratamento deste quadro clínico. Este novo método é considerado menos invasivo e com menor comorbidade, uma vez que se trata da instalação de uma endoprótese por meio de catéter através da artéria femoral. Neste trabalho, será verificado o escoamento através de três aneurismas de aorta abdominal (AAA) e das endopróteses indicadas para o tratamento de cada um dos aneurismas. Foram feitas simulações computacionais afim de se obter as pressões, as velocidades do escoamento sanguíneo e as tensões de cisalhamento na parede das geometrias, usando pulsos de pressão e velocidade fisiológico de um individuo adulto, normotenso, em repouso. No modelo de escoamento simulado, foi adotado o sangue como fluido Newtoniano, incompressível e homogêneo. Foi usado um modelo de turbulência K-, com interpolador upwind de 2ª ordem e tratamento de parede nas geometrias, para que se fosse possível obter resultados satisfatórios (das camadas próximas à parede, e de todos os vórtices). Os resultados obtidos no trabalho foram satisfatórios, uma vez que eles expressaram de forma realista o comportamento do escoamento sanguíneo pelos aneurismas e endopróteses. Foi possível justificar com esse trabalho a instalação de endopróteses em pacientes, quando necessário, com o objetivo de diminuir significativamente a degradação do vaso, causando a ruptura do aneurisma. / Aneurisms are permanently dilatation higher than 50% of the original diameter of an artery or of the proximal diameter of them, according to the published consensus of the Vascular Surgery Society of North America and International Society of Cardiovascular Surgery on 1991 (Vliet and Boll, 1997). Aortas Aneurism is a vascular disease that affects more than 5% of the male population, with more than 55 years old (How et al, 2005). Since 1991, a new method is used in the treatment of these diseases. This new method is less invasive and has less comorbidity. This method is provided by the installation of an endoprosthesis through the catheter through the femoral artery. In this work, the flow will be verified through three abdominal aortic aneurysms (AAA) and the endoprosthesis indicated for the treatment of each of the aneurysms. Computational simulations were made in order to obtain the pressures, velocities of the blood flow and the shear stresses on the wall of geometries, using a pulse pressure and velocity of an individual physiological adult normotensive at rest. For the fluid simulations, it was adopted the blood as Newtonian fluid, incompressible and homogeneous. In simulations, it was used a K- model of turbulence, with 2nd order upwind interpolator and wall geometry treatment in order to obtain satisfied results (on the layers near the walls, and all the vortices). The results obtained in this work were satisfied, once they expressed the realistic behavior of the blood flow through the aneurysm and the endoprosthesis. It was possible to justify with this work the installation of an endoprosthesis inside patients, when it is necessary, in order to decrease significantly the vessels degradation, causing the aneurysm rupture.