Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-03-07T19:04:39Z No. of bitstreams: 1 lucasdiegomotameneses.pdf: 10631997 bytes, checksum: be72daf41245404c708aab9a8c58d9a1 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-03-10T12:23:50Z (GMT) No. of bitstreams: 1 lucasdiegomotameneses.pdf: 10631997 bytes, checksum: be72daf41245404c708aab9a8c58d9a1 (MD5) / Made available in DSpace on 2017-03-10T12:23:50Z (GMT). No. of bitstreams: 1 lucasdiegomotameneses.pdf: 10631997 bytes, checksum: be72daf41245404c708aab9a8c58d9a1 (MD5) Previous issue date: 2016-09-30 / Modelos computacionais de árvores arteriais são utilizados como substratos geométricos em simulações hemodinâmicas. A construção destes modelos é mandatória para adequada representação das redes vasculares periféricas devido à escassez de dados anatômicos destas redes. Os modelos relatados na literatura são classificados em: anatômico, a parâmetro condensado, fractal e otimizados. O crescimento dos modelos fractais e otimizados dependem de uma lei de bifurcação, que controla a relação entre os raios dos vasos envolvidos na bifurcação através de um expoente. Neste trabalho, investiga-se a construção de modelos otimizados inspirados no método CCO (Constrained Constructive Optimization) usando novas abordagens para a escolha do expoente da lei de bifurcação. Estas estratégias são formuladas com funções degrau e sigmoidal dependentes do número de bifurcações proximais. Os dados morfométricos dos modelos são comparados com outros experimentais e teóricos da literatura. Os resultados obtidos comprovam que o expoente de bifurcação influencia nas estruturas geométrica e topológica dos modelos. / Computational models of arterial trees are used as geometric substrates in hemodynamic simulations. The construction of these models is mandatory for appropriated representation of the peripheral vascular networks due to lack of anatomical data of these networks. The models reported in the literature are classified into: anatomical, lumped parameter, fractal and optimized. The growth of the fractal and optimized models depend on a bifurcation law, which controls the relationship between the radii of the vessels involved in the bifurcation through an exponent. This work investigates the construction of optimized models inspired by the CCO (Constructive Constrained Optimization) method using new approaches to the choice of the exponent of the bifurcation law. Theses strategies are formulated as step and sigmoid functions depend on number of proximal bifurcations. Morphometric data from models are compared with other experimental and theoretical data of the literature. The results obtained show that the bifurcation exponent influences the geometrical and topological structures of the models.

Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-02-13T11:12:52Z No. of bitstreams: 1 patriciafonsecadebrito.pdf: 15405226 bytes, checksum: d3d134135b13194c75ee40afae239681 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-02-13T16:45:56Z (GMT) No. of bitstreams: 1 patriciafonsecadebrito.pdf: 15405226 bytes, checksum: d3d134135b13194c75ee40afae239681 (MD5) / Made available in DSpace on 2017-02-13T16:45:56Z (GMT). No. of bitstreams: 1 patriciafonsecadebrito.pdf: 15405226 bytes, checksum: d3d134135b13194c75ee40afae239681 (MD5) Previous issue date: 2016-09-13 / FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais / Modelos de árvores arteriais têm sido utilizados com sucesso para obter uma melhor compreensão de todos os aspectos relacionados à hemodinâmica de regiões clinicamente relevantes do corpo humano, passando pelo diagnóstico e com aplicações no planejamento cirúrgico. A principal motivação para a construção desses modelos é a dificuldade em se obter dados anatômicos suficiêntes que permitam descrever em detalhes as estruturas geométrica e topológica de redes arteriais periféricas. Basicamente, os modelos podem ser classificados em: anatômico, parâmetro condensado, fractal e otimizado. Neste trabalho, foca-se na geração de modelos otimizados no contexto do método CCO (Constrained Constructive Optimization). Tal método é capaz de gerar modelos de árvores arteriais que reproduzem características de árvores coronarianas reais, como perfis de pressão, diâmetro dos vasos e distribuição dos ângulos de bifurcação. No entanto, este método não considera uma viscosidade sanguínea realística durante a geração dos modelos, ou seja, despreza o efeito Fahraeus-Lindqvist, o qual indica que a viscosidade sanguínea depende não linearmente do diâmetro do vaso no qual o sangue está escoando e da descarga de hematócrito. Neste contexto, no trabalho investiga-se um algoritmo inspirado no método CCO que leva em conta tal efeito durante a construção de modelos de árvores arteriais. Diversos cenários de simulações 2D/3D empregando este algoritmo foram realizados com intuito de estudar a influência da escolha da viscosidade sanguínea nas propriedades morfométricas e hemodinâmicas dos modelos. Os resultados obtidos nos indicam que a viscosidade sanguínea afeta a distribuição dos raios dos segmentos, a arquitetura e os perfis de pressão dos modelos gerados através de simulações no computador. Além disso, estes modelos in silico são condizentes com árvores arteriais coronarianas reais. / Arterial tree models have been successfully used to gain a better understanding of all hemodynamics aspects of clinically relevant regions of the human body, including diagnosis and applications in surgical planning. The main motivation for the construction of these models is the difficulty to obtain sufficient anatomical data to describe in detail the geometrical and topological structures of peripheral arterial networks. Basically, the models can be classified into: anatomical, lumped parameter, fractal and optimized. This work focuses on the generation of optimized models based on Constructive Constrained Optimization (CCO) method. CCO is capable of generating arterial tree models that reproduce characteristics of real coronary tree, such as pressure profiles, vessel diameter and bifurcation angle distribution. However, this method does not consider a realistic blood viscosity during the generation of models, i.e., it disregards the F˚ahraeus-Lindqvist effect, which indicates that the blood viscosity depends nonlinearly on diameter of the vessel in which blood is draining and on discharge of hematocrit. In this context, the work investigates an algorithm that takes into account this effect during the construction of models of arterial trees. Several scenarios of 2D/3D simulations using this algorithm were done in order to study the influence of the choice of blood viscosity on morphometric and hemodynamic properties of the models. The results indicate that the blood viscosity affects the distribution of vessel radii, the architecture and pressure profiles of the models generated through computer simulations. Furthermore, these in silico models are consistent with real coronary arterial trees.

The geometry of an organ’s vascular system determines the blood flow distribution to tissues for exchange of gas and nutrients by determining its vascular resistance. The importance of vascular geometry is evident in the placenta, where insufficient fetoplacental vascularity elevates vascular resistance thereby impairing perfusion, leading to one of the most common and severe pregnancy complications, intrauterine growth restriction (IUGR). The mouse is becoming a widely used model for human placental development due to the increasing availability of mouse models thought to have a placental defect. Vascular geometry can now be imaged and quantified using micro-computed tomography (micro-CT) and results used to estimate resistance to blood flow. This thesis first describes the implementation of contrast agent perfusion and micro-CT imaging of the mouse fetoplacental vasculature throughout late gestation. Application of a vascular segmentation technique is then described and evaluated for quantification of the arterial fetoplacental tree. Normal fetoplacental vascular development in late gestation is described for two common mouse strains, CD1 and C57Bl6 (B6). In B6 placentas, both late gestational capillary growth and thinning of the interhaemal membrane were blunted relative to CD1. Analysis of CD1 and B6 tree geometry revealed a constant number of arterial segments throughout late gestation in both strains but expansion of arterial diameters in B6 only, resulting in decreased B6 arterial resistance and shear stress in late gestation. Strain dependence shows the importance of genetics in fetoplacental vascular development. Quantification of the arterial tree in a mouse model of maternal pre-pregnancy exposure to chemicals commonly found in cigarettes revealed an increase in vascular tortuousity and a reduced number of arteriole sized vessels. This led to an increase in vascular resistance and a predicted decrease in blood flow, which could contribute to the observed reduction in fetal weights. In future studies, the methods described herein can be used in phenotyping numerous mouse models which currently are suspected to have a placental vascular defect.

The geometry of an organ’s vascular system determines the blood flow distribution to tissues for exchange of gas and nutrients by determining its vascular resistance. The importance of vascular geometry is evident in the placenta, where insufficient fetoplacental vascularity elevates vascular resistance thereby impairing perfusion, leading to one of the most common and severe pregnancy complications, intrauterine growth restriction (IUGR). The mouse is becoming a widely used model for human placental development due to the increasing availability of mouse models thought to have a placental defect. Vascular geometry can now be imaged and quantified using micro-computed tomography (micro-CT) and results used to estimate resistance to blood flow. This thesis first describes the implementation of contrast agent perfusion and micro-CT imaging of the mouse fetoplacental vasculature throughout late gestation. Application of a vascular segmentation technique is then described and evaluated for quantification of the arterial fetoplacental tree. Normal fetoplacental vascular development in late gestation is described for two common mouse strains, CD1 and C57Bl6 (B6). In B6 placentas, both late gestational capillary growth and thinning of the interhaemal membrane were blunted relative to CD1. Analysis of CD1 and B6 tree geometry revealed a constant number of arterial segments throughout late gestation in both strains but expansion of arterial diameters in B6 only, resulting in decreased B6 arterial resistance and shear stress in late gestation. Strain dependence shows the importance of genetics in fetoplacental vascular development. Quantification of the arterial tree in a mouse model of maternal pre-pregnancy exposure to chemicals commonly found in cigarettes revealed an increase in vascular tortuousity and a reduced number of arteriole sized vessels. This led to an increase in vascular resistance and a predicted decrease in blood flow, which could contribute to the observed reduction in fetal weights. In future studies, the methods described herein can be used in phenotyping numerous mouse models which currently are suspected to have a placental vascular defect.

It is known that there are many cardiovascular diseases caused by the alterations in the blood vessels, that affect most of the world population. The knowledge of the mechanobiological behavior of blood vessels is used for understanding how cardiovascular diseases could affect the human body. So, by studying the growth and remodeling (G&R) of the arterial tree, it is possible to predict how these diseases will develop and consequently, how they can be treated or even prevented. The human body naturally tries to find the optimum steady-state by changing either the production of the constituents of the arteries or the flow rate through blood vessels. This effect is the phenomenon that is going to be studied in this thesis and these three main factors have to be taken into account when reproducing the diseases’ effects: the so-called transmural pressure, the blood flow rate, and the biomechanics of the constituents which form the arterial wall. Therefore, through numerical simulations the variation of these factors can be predicted, although always with a reliability supported by experimental data. / Se sabe que hay muchas enfermedades cardiovasculares causadas por alteraciones en los vasos sanguíneos que afectan gran parte de la población mundial. El conocimiento del comportamiento mecanobiológico de los vasos sanguíneos se usa para entender cómo estas enfermedades puede afectar al cuerpo humano. Así, estudiando el crecimiento y desarrollo (G&R) del árbol arterial, es posible predecir cómo estas enfermedades se van a desarrollar y consecuentemente, cómo pueden tratarse o incluso prevenirse. El cuerpo humano tiende a buscar un estado de equilibrio óptimo de forma natural cambiando o bien la producción de los constituyentes de las arterias o bien el flujo de sangre que atraviesa los vasos sanguíneos. Este efecto es el fenómeno que va a ser estudiado en esta tesis y se ha de tener en cuenta tres factores principales cuando se quiere reproducir los efectos de dichas enfermedades: la presión transmural, el flujo de sangre y la biomecánica de los constituyentes que forman la pared arterial. Luego, a través de simulaciones numéricas la variación de estos factores puede ser predicha, aunque siempre con una veracidad aportada por datos experimentales. / Vascular occlusion, modelling, arteries, arterial tree, growth and remodelling, Murray, cerebrocardiovascular diseases, adaptation, thrombosis, calcification, anemia, polycythemia, isquemia, edema

This Mater's thesis deals with the evaluation of pulse wave velocity using multi-channel whole-body impedance cardiography. Data were taken from the group of healthy volunteers whose impedance changes were measured during rest, respiratory maneuvers, tilt and stress exercise. The result of this measurement are values of peaks of pulse wave time shifts towards R-wave. The velocity values towards the thorax electrodes were recalculated on the basis of knowledge about the pulse wave time shifts and the distances from the heart to the scanned locations, which were measured using the arterial segment's lengths.