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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Desenvolvimento de tecnologia de biofabricação com laser infravermelho para recobrimento de próteses articulares com hidrogel / Development of biofabrication technology with Infrared laser to coating of articular prostheses with hydrogel

Passos, Marcele Fonseca, 1986- 19 August 2018 (has links)
Orientador: Passos, Marcele Fonseca / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-19T02:23:46Z (GMT). No. of bitstreams: 1 Passos_MarceleFonseca_M.pdf: 15093576 bytes, checksum: fc209e9f43b60067bf5b99f169881ea4 (MD5) Previous issue date: 2011 / Resumo: Na área dos materiais, um campo em crescente expansão é o desenvolvimento de hidrogéis poliméricos para aplicações biomédicas. Entre a grande classe de hidrogéis poliméricos estudados, o poli 2-hidróxi etil metacrilato (pHEMA) recebe especial atenção, devido a sua biocompatibilidade, alta hidrofilicidade e fácil preparação. Para aplicação como substituinte da cartilagem articular natural em próteses articulares, as quais, normalmente apresentam como principal componente (substrato) o polietileno de ultra alto peso molecular (PEUAPM), a adesão do sistema (hidrogel - substrato) ainda é um parâmetro a ser avaliado. Modificações adequadas no material e considerações de projeto, no entanto, podem melhorar a aderência do conjunto, via embricamento mecânico. Dentro de um grupo multidisciplinar e em ascensão, Instituto Nacional de C&T em Biofabricação - BIOFABRIS, este projeto, teve como objetivo, desenvolver novos biomateriais, usando técnicas de engenharia para obtenção de dispositivos biomédicos (próteses e órteses ortopédicas). Foi desenvolvida uma tecnologia de biofabricação visando melhorar as propriedades mecânicas dos hidrogéis de pHEMA, bem como obter uma adesão adequada entre este polímero e a superfície articular artificial, a fim de minimizar o desgaste sofrido pelos componentes que constituem os dispositivos ortopédicos, um dos principais fatores que geram sua falência. Usando a técnica de biofabricação, foi possível obter hidrogéis de pHEMA desde a simulação do produto até a caracterização final, para aplicações específicas: cartilagem articular artificial, foco principal da dissertação; e, como cartilagem reconstrutiva, atuando como suporte ao crescimento de células (hidrogéis porosos). A avaliação do mecanismo de polimerização e reticulação do pHEMA, o calor específico e a condutividade térmica da solução do 2-hidróxi etil metacrilato (HEMA) foram obtidos via técnica de Calorimetria Exploratória Diferencial. Tais parâmetros serviram de subsídio para a simulação computacional, a qual permitiu estimar os parâmetros do processo de reticulação do pHEMA, como potência do laser a 30 W e tempo reacional de 120 segundos, na temperatura de 399 K. As propriedades térmicas, como temperatura de transição vítrea e degradação, apresentaram valores similares aos dados encontrados na literatura, na faixa de 109 e 118 ºC, e na faixa de 354 e 376 ºC, respectivamente. Os resultados obtidos do coeficiente de atrito do par tribológico PEUAPM-pHEMA apresentaram valores altos, contudo, a tecnologia de biofabricação desenvolvida neste projeto, mostrou-se uma importante ferramenta para a obtenção de biomateriais para aplicações diversificadas / Abstract: In the materials field, a rapidly expanding field is the development of polymeric hydrogels for biomedical applications. Among the large class of polymeric hydrogels studied, poly 2-hydroxy ethyl methacrylate (pHEMA) receives special attention. For application as replacements of natural articular cartilage in articular prostheses, which usually present as a main component (substrate) the polyethylene of ultra high molecular weight (UHMWPE), the adhesion of system (hydrogel - substrate) is still a parameter to be evaluated. Appropriate modifications in the material and design considerations, however, can improve the adhesion of the set by embrication mechanic. Within a multidisciplinary group and on the rise, National Institute of C & T in Biofabrication -BIOFABRIS, this project aims to develop new biomaterials using engineering techniques for obtaining biomedical devices (prostheses and orthoses, orthopedic). It was developed a technology aiming to both improve the mechanical properties of pHEMA hidrogel as well as to obtain proper adhesion between this polymer and the artificial articular surface in order to minimize the wear suffered by the components that constitute the orthopedic devices, one of the main factors that cause bankruptcy. Using the technique of biofabrication was possible to obtain hydrogels pHEMA from the simulation of the product until the final characterization, for specific applications: artificial articular cartilage, the main focus of the dissertation, and as a reconstructive cartilage, acting as a support cell growth (porous hydrogels). The evaluation of the mechanism of polymerization and crosslinking of pHEMA, the specific heat and thermal conductivity of the solution of 2-hydroxy ethyl methacrylate (HEMA) were obtained by the technique of Differential Scanning Calorimetry. These parameters served as input to the computer simulation, which allowed to estimate the process parameters of pHEMA crosslinking, such as laser power 30 W and the reaction time of 120 seconds at a temperature of 399 K. The thermal properties and glass transition temperature and degradation, showed values similar to those found in the literature, to know, in the range of 109 and 118 °C, and in the range of 354 and 376 °C, respectively. The obtained results of the friction coefficient for the tribological pair UHMWPE-pHEMA have demonstrated high values, however, the biofabrication technology developed in this project, was important a tool for obtaining biomaterials for different applications / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química
2

Harnessing osteopontin and other natural inhibitors to mitigate ectopic calcification of bioprosthetic heart valve material /

Ohri, Rachit. January 2003 (has links)
Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 104-125).
3

Electrospinning controlled architecture scaffolds for tissue engineering & the effect of scaffold mechanical properties on collagen synthesis in tissue engineered mitral valves /

Mitchell, Stuart B. January 2004 (has links)
Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (p. 123-133).
4

Aortic valve replacement with stentless bioprostheses : prospective long-term studies of the Biocor and the Toronto SPV /

Dellgren, Göran, January 2002 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst., 2002. / Härtill 6 uppsatser.
5

Análise semiquantitativa da reação inflammatória e quantitativa da deposição colágena de telas de polipropileno monofilamentar recobertas com matriz polimérica eluidora de S-nitrosoglutationa implantadas no subcutãneo de ratas adultas / Semi quantitative analysis of inflammatory reaction and quantitative collagen deposition evaluation of monofilament polypropylene mesh coated with S-nitrosoglutathione-releasing poly (vinyl alcohol) film implanted in subcutneous o female rats

Santos, Alessandro Corrêa Prudente dos, 1978- 16 August 2018 (has links)
Orientadores: Cássio Luís Zanettini Riccetto, Marcelo Ganzarolli de Oliveira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-16T02:05:33Z (GMT). No. of bitstreams: 1 Santos_AlessandroCorreaPrudentedos_M.pdf: 2396933 bytes, checksum: 15e0ba5362fd0f6648c8ca4f6aea3f8c (MD5) Previous issue date: 2010 / Resumo: Introdução: A introdução de telas de polipropileno no reparo de incontinência urinária e distopias genitais diminuiu a recorrência do problema, mas também trouxe o inconveniente de complicações como extrusões vaginais. O óxido nítrico (NO) tem propriedades vasodilatadoras e moduladoras dos processos inflamatórios. Assim, o recobrimento das telas com matriz polimérica eluidora de um carreador de NO pode modificar a resposta tecidual ao implante em organismos biológicos. Objetivo: Estudar o efeito do recobrimento com matriz polimérica eluidora do carreador de NO, S-nitrosoglutationa (GSNO), na resposta biológica tecidual de telas de polipropileno (PP) monofilamentar implantadas no subcutâneo de ratas adultas. Materiais e Métodos: Utilizaram-se 20 ratas fêmeas da raça Wistar (peso médio= 250 g). Cada animal recebeu o implante de 4 fragmentos de tela medindo 10 x 10 mm no subcutâneo. As amostras obtidas dos animais foram divididas em 7 grupos, designados como: grupo PP - tela de PP sem recobrimento (grupo controle) (n=20); grupo PVA -tela de PP com recobrimento de poli(alcool vinílico) (n=10); grupo PVA/PVP - tela de PP com recobrimento de blenda de poli(alcool vinílico)/poli(vinil pirrolidona) (n=10); grupo PVA/GSNO 1 - tela de PP com recobrimento de poli(alcool vinílico), contendo GSNO 1 mM (n=10); grupo PVA/GSNO 10 - tela de PP com recobrimento de poli(alcool vinílico) contendo GSNO 10mM (n= 10), grupo PVA/PVP/GSNO 1 - tela de PP com recobrimento de poli(álcool vinílico)/poli(vinil pirrolodona), contendo GSNO 1mM (n=10); grupo PVA/PVP/GSNO 10 - tela de PP com recobrimento de poli(alcool vinílico)/poli(vinil pirrolodona) contendo GSNO 10mM (n= 10). Dez ratas foram eutanasiadas após 2 dias e outras dez após 21 dias do procedimento cirúrgico. Após a eutanásia, uma excisão em bloco da parede abdominal foi feita para análises microscópicas. Infiltrado inflamatório, edema e angiogênese foram avaliados em lâminas coradas com Hematoxilina-Eosina (HE). A deposição colágena foi avaliada em lâminas coradas com Picrosirius Red. As variáveis estudadas nas lâminas HE foram categorizadas em ausente, leve, moderado ou intenso. A formação colágena foi quantificada com método estereológico. Todas as avaliações foram feitas pelo mesmo pesquisador, que não sabia de que animal ou fragmento se tratava a lâmina que estava analisando. Resultados: Nas ratas eutanasiadas após dois dias do procedimento, não se identificou diferença estatística entre os diversos tratamentos. No entanto, naquelas estudadas após 21 dias do implante, observou-se menor edema (p=0.0039) tecidual e maior angiogênese (p=0.0031) no grupo PVA/GSNO 1. O grupo PVA também demonstrou maior formação vascular que o controle (p=0.0027). Além disso, ratas eutanasiadas aos 21 dias apresentaram maior infiltrado inflamatório (p= 0,0474) e menor edema (p=0,0064) quando comparadas àquelas aos 2 dias. Na quantificação de fibras colágenas, não houve diferença significativa entre os fragmentos. Conclusões: O recobrimento com PVA e PVA contendo GSNO modificou a resposta biológica tecidual de telas de PP monofilamentar implantadas no subcutâneo de ratas adultas. O recobrimento com PVA, isoladamente ou contendo GSNO 1mM demonstrou efeito angiogênico. O grupo PVA/GSNO 1 apresentou, ainda, redução do edema. Não houve diferenças significativas da deposição colágena / Abstract: Introduction: The use of polypropylene (PP) mesh to repair urinary incontinence and vaginal prolapse has decreased recurrence. However, it has also been related to specific complications such as vaginal erosions. Nitric oxide (NO) can produce vasodilatation and modulate inflammatory reaction. The NO containing (S-nitrosoglutathione - GSNO) eluted from a polymeric coating could modify tissue response of meshes. Objective: To study the effect of a NO containing (S-nitrosoglutathione - GSNO) eluted from a polymeric coating in the tissue response of monofilament polypropylene mesh implanted in subcutaneous of rats. Materials and Methods: Twenty adult female Wistar rats were used (mean weight: 250g). Four mesh fragments measuring 10 x 10 mm were implanted in subcutaneous tissue of each rat. The samples were divided in 7 groups: PP group - PP mesh without coating (control) (n=20); PVA group - PP mesh coated with poly(vinyl alcohol) (PVA) (n=10); PVA/PVP group - PP mesh coated with a solution of poly(vinyl alcohol) and poly(vinyl pyrrolidone) (PVA/PVP) (n=10); PVA/GSNO 1 group - PP mesh coated with PVA containing GSNO 1mM (n=10); PVA/GSNO 10 group - PP mesh coated with PVA containing GSNO 10mM (n=10); PVA/PVP/GSNO 1 group - PP mesh coated with PVA/PVP containing GSNO 1mM (n=10); PVA/PVP/GSNO 10 group - PP mesh coated with PVA/PVP containing GSNO 10mM (n=10);. Ten rats were euthanized at 2 days and the other at 21 days postoperatively. Abdominal wall was excised en bloc for microscopic analyses. Inflammatory infiltrate, edema and angiogenesis were analyzed in hematoxilin-eosin (HE) slices and categorized as absent, mild, moderate or severe. The collagen deposition was stained with Picrosirius red and quantified using stereological method. The same researcher did all evaluations without knowing what fragment he was analyzing. Results: No statistical difference was identified among treatments in euthanized rats at two days after the implants. However, in rats studied at 21 days, less edema (p=0.0039) and greater angiogenesis (p=0.0031) were observed for PVA/GSNO 1 group. PVA group also was related to induced a higher angiogenesis (p=0.0027). Furthermore, euthanized rats at 21 days demonstrated a greater inflammatory infiltrate (p= 0,0474) and less edema (p= 0,0064) than those at two days. In collagen deposition analyses no statistical difference was identified among treatments. Conclusion: Coating monofilament PP meshes with GSNO-containing PVA modified the tissue response when implanted in subcutaneous of rats. The PVA alone or with GSNO 1 showed angiogenic effect. The PVA/GSNO1 group presented less edema too. There were not effects in collagen deposition / Mestrado / Cirurgia / Mestre em Cirurgia
6

Estudo experimental de escoamento pulsátil através de biopróteses valvulares cardíacas mitrais a partir do desenvolvimento de um simulador do lado esquerdo do coração. / Experimental study pulsatile flow through mitral heart bioprosthesis based on the development of a left human heart cardiac simulator.

Ovandir Bazan 26 March 2014 (has links)
Uma vez que a maioria das complicações relacionadas ao funcionamento das próteses de válvulas cárdicas é devida aos distúrbios de escoamento, a sua caracterização hidrodinâmica é um auxílio útil no projeto de novas válvulas. Simulações do escoamento pulsátil através de próteses de válvulas cardíacas começaram há cerca de 60 anos, por meio do desenvolvimento de diferentes simuladores cardíacos, melhorando a interpretação dos resultados clínicos. Para o presente estudo, um simulador cardíaco foi desenvolvido completamente na Escola Politécnica da Universidade de São Paulo, no Departamento de Engenharia Mecânica, para estudar o fluxo através de próteses mitrais e aórticas. A sua concepção é baseada na geometria e na fisiologia do lado esquerdo do coração humano, no estado da arte desses simuladores e na norma ISO 584:2010. Neste trabalho, o simulador cardíaco desenvolvido foi aplicado para estudar experimentalmente o fluxo pulsátil através de próteses cardíacas mitrais biológicas de pericárdio bovino. Para tanto, após a validação do simulador para algumas freqüências cardíacas, as biopróteses foram submetidas a ensaios de velocimetria não invasiva, por meio de um equipamento Particle Image Velocimetry (PIV). Os experimentos, que se concentraram principalmente logo após o começo da diástole, mostraram qualitativamente uma diferença significativa no escoamento intraventricular em função de dois posicionamentos das biopróteses, defasadas entre si de 180º no sentido do seu eixo longitudinal. Além disso, produziram significativas mudanças no escoamento próximo à prótese aórtica considerada. Com a continuidade deste estudo, os resultados poderão induzir a um dado procedimento clínico. / Since most complications related to the operation of prosthetic heart valves are due to disturbances of flow, their hydrodynamic characterization is a useful aid in the design of new prostheses. Simulations of pulsatile flow in cardiac prostheses began nearly 60 years ago, through the development of different mock human circulatory systems, improving the clinical results interpretation. A complete design of a cardiac simulator was developed at Polytechnic School of USP, Mechanical Engineering Department, to study mitral and aortic prosthetic heart valves. The simulator design is based on the both geometry and physiology of the left side of the human heart, on state-of-art studies and also considering the ISO 584:2010 standard. The cardiac simulator was applied to pulsatile flow testing of bovine pericardium mitral prosthetic valves. For this, after the cardiac simulator validation for some heart rates, the bioprostheses were assayed by noninvasive velocimetry technics, i.e., a Particle Image Velocimetry (PIV) system. The testing, which mainly were focused on just after the beginning of diastole, qualitatively have showed a significant difference in the intraventricular flow according two different positions for the bioprostheses, dephased of 180° in the direction of their longitudinal axis. Moreover, they produced significant changes in flow close to the aortic prosthesis considered. Future works may lead to a particular medical procedure.
7

Avalia??o anatomopatologica de rins, f?gado e ba?o de camundongos submetidos ao reparo de ferida cir?rgica em parede abdominal com fragmentos de peric?rdio bovino conservado com glicerina e glutaralde?do. / Histopathological evaluation of kidneys, liver and spleen of mice undergoing repair of surgical wound in the abdominal wall with pieces bovine pericardium preserved with glycerin and glutaraldehyde

Martins, Caroline Rodrigues Pereira 29 October 2009 (has links)
Made available in DSpace on 2016-04-28T20:18:34Z (GMT). No. of bitstreams: 1 Caroline Rodrigues Pereira Martins.pdf: 1134388 bytes, checksum: fa8d41a81a1364e1de4a2a59b34737ed (MD5) Previous issue date: 2009-10-29 / The use of bovine pericardium as a biological membrane is widespread in surgical repair because of the low cost, good applicability and it is easily obtained. Glycerin 98% is the chemical agent most used as a biological tissue preservative in veterinary medicine, but studies show it is ineffective in eliminating viruses. Glutaraldehyde is a biological tissue preservative widely used in 0.5% and 0.625% concentrations. However, the persistence of rabies virus in samples of mice pericardium preserved in 0.625% glutaraldehyde was proven, and probably higher concentrations are required for virucidal action. Given its toxic capacity, this study aims to evaluate macro-and microscopically kidney, liver and spleen of 65 mice, 60 of whom underwent implantation of bovine pericardium preserved in glycerin 98% and 0.625%, 1% and 1.5% glutaraldehyde, and 5 non-implanted mice served as controls. The animals implanted, the same used in other research to evaluate local reaction on the abdominal wall implants, were euthanized after 7, 14 and 30 days after implantation of the pericardium, and the spleens, livers and kidneys were assessed as to their macro and microscopic features. Fragments of these organs were collected, fixed in buffered formalin 10%, processed by usual histopathologic methods and stained with hematoxylin and eosin. There was no macro or microscopic changes that could be related to the toxicity of these substances / O emprego de peric?rdio bovino, como membrana biol?gica, ? bastante difundido em t?cnicas de reparos cir?rgicos devido ? facilidade de aquisi??o, baixo custo e boa aplicabilidade. A glicerina 98% ? o agente qu?mico mais utilizado como conservante de tecidos biol?gicos em medicina veterin?ria, por?m estudos comprovam sua inefic?cia na elimina??o viral. O glutaralde?do ? um conservante de tecidos biol?gicos e suas concentra??es mais difundidas s?o de 0,5% e 0,625%. Entretanto, a persist?ncia do v?rus r?bico em amostras de peric?rdio de camundongos conservadas em glutaralde?do 0,625% foi comprovada, sendo, provavelmente, necess?rias concentra??es mais altas para a??o virucida. Sabendo-se da sua capacidade t?xica, este estudo teve como objetivo, avaliar macro e microscopicamente rins, f?gado e ba?o de 65 camundongos, dos quais 60 foram submetidos a implante de peric?rdio bovino conservado em glicerina 98% e glutaralde?do a 0,625%, 1% e 1,5% e 5 camundongos n?o implantados que serviram como controles. Os animais implantados, os mesmos utilizados em outra pesquisa para avalia??o das caracter?sticas reacionais locais nas paredes abdominais aos implantes, foram eutanasiados ap?s 7, 14 e 30 dias ap?s a implanta??o do peric?rdio; e os ba?os, f?gados e rins foram avaliados quanto ?s caracter?sticas macro e microsc?picas. Fragmentos desses ?rg?os foram coletados, fixados em formol a 10% tamponados, processados pelos m?todos usuais para histopatologia e corados pela hematoxilina e eosina. N?o foram evidenciadas altera??es macro ou microsc?picas que pudessem estar relacionadas ? toxicidade destas subst?ncias.
8

Processing and exploration of CT images for the assessment of aortic valve bioprostheses

Wang, Qian 09 December 2013 (has links) (PDF)
The aim of the study was to assess the feasibility of CT based 3D analysis of degenerated aortic bioprostheses to make easier their morphological assessment. This could be helpful during regular follow-up and for case selection, improved planning and mapping of valve-in-valve procedure. The challenge was represented by leaflets enhancement because of highly noised CT images. Contrast-enhanced ECG-gated CT scan was performed in patients with degenerated aortic bioprostheses before reoperation (in-vivo images). Different methods for noise reduction were tested and proposed. 3D reconstruction of bioprostheses components was achieved using stick based region segmentation methods. After reoperation, segmentation methods were applied to CT images of the explanted prostheses (exvivo images). Noise reduction obtained by improved stick filter showed best results in terms of signal to noise ratio comparing to anisotropic diffusion filters. All segmentation methods applied to the best phase of in-vivo images allowed 3D bioprosthetic leaflets reconstruction. Explanted bioprostheses CT images were also processed and used as reference. Qualitative analysis revealed a good concordance between the in-vivo images and the bioprostheses alterations. Results from different methods were compared by means of volumetric criteria and discussed. A first approach for spatiotemporal visualization of 3D+T images of valve bioprosthesis has been proposed. Volume rendering and motion compensation techniques were applied to visualize different phases of CT data. Native valve was also considered. ECG-gated CT images of aortic bioprostheses need a preprocessing to reduce noise and artifacts in order to enhance prosthetic leaflets. Stick based methods seems to provide an interesting approach for the morphological characterization of degenerated bioprostheses.
9

Processing and exploration of CT images for the assessment of aortic valve bioprostheses / Traitement et exploration d'images TDM pour l'évaluation des bioprothèses valvulaires aortiques

Wang, Qian 09 December 2013 (has links)
Le but de cette étude est d’évaluer la faisabilité de l’analyse tomodensitométrique 3D des bioprothèses aortiques pour faciliter leur évaluation morphologique durant le suivi et d’aider la sélection de cas et améliorer la planification d’une procédure valvein-valve. Le challenge était représenté par le rehaussement des feuillets valvulaires, en raison d’images très bruitées. Un angio-scanner synchronisé était réalisé chez des patients porteurs d’une bioprotèses aortique dégénérée avant réintervention (images in-vivo). Différentes méthodes pour la réduction du bruit étaient proposées. La reconstruction tridimensionnelle des bioprothèses était réalisée en utilisant des méthodes de segmentation de régions par "sticks". Après réopération ces méthodes étaient appliquées aux images scanner des bioprothèses explantées (images ex-vivo) et utilisées comme référence. La réduction du bruit obtenue par le filtre stick modifié montrait meilleurs résultats en rapport signal/bruit en comparaison aux filtres de diffusion anisotropique. Toutes les méthodes de segmentation ont permis une reconstruction 3D des feuillets. L’analyse qualitative a montré une bonne concordance entre les images obtenues in-vivo et les altérations des bioprothèses. Les résultats des différentes méthodes étaient comparés par critères volumétriques et discutés. Les bases d'une première approche de visualisation spatio-temporelle d'images TDM 3D+T de la prothèse valvulaire ont été proposés. Elle implique des techniques de rendu volumique et de compensation de mouvement. Son application à la valve native a aussi été envisagée. Les images scanner des bioprothèses aortiques nécessitent un traitement de débruitage et de réduction des artéfacts de façon à permettre le rehaussement des feuillets prothétiques. Les méthodes basées sticks semblent constituer une approche pertinente pour caractériser morphologiquement la dégénérescence des bioprothèses. / The aim of the study was to assess the feasibility of CT based 3D analysis of degenerated aortic bioprostheses to make easier their morphological assessment. This could be helpful during regular follow-up and for case selection, improved planning and mapping of valve-in-valve procedure. The challenge was represented by leaflets enhancement because of highly noised CT images. Contrast-enhanced ECG-gated CT scan was performed in patients with degenerated aortic bioprostheses before reoperation (in-vivo images). Different methods for noise reduction were tested and proposed. 3D reconstruction of bioprostheses components was achieved using stick based region segmentation methods. After reoperation, segmentation methods were applied to CT images of the explanted prostheses (exvivo images). Noise reduction obtained by improved stick filter showed best results in terms of signal to noise ratio comparing to anisotropic diffusion filters. All segmentation methods applied to the best phase of in-vivo images allowed 3D bioprosthetic leaflets reconstruction. Explanted bioprostheses CT images were also processed and used as reference. Qualitative analysis revealed a good concordance between the in-vivo images and the bioprostheses alterations. Results from different methods were compared by means of volumetric criteria and discussed. A first approach for spatiotemporal visualization of 3D+T images of valve bioprosthesis has been proposed. Volume rendering and motion compensation techniques were applied to visualize different phases of CT data. Native valve was also considered. ECG-gated CT images of aortic bioprostheses need a preprocessing to reduce noise and artifacts in order to enhance prosthetic leaflets. Stick based methods seems to provide an interesting approach for the morphological characterization of degenerated bioprostheses.
10

Caracterização In Vitro e In Vivo do pericárdio bovino reticulado com acetais do glutaraldeído para manufatura de biopróteses valvulares cardíacas. / Characterization in vitro and in vivo of bovine pericardium cross-linked with glutaraldehyde acetals for the manufacture of cardiac valve bioprostheses.

Sergio Akinobu Yoshioka 02 June 2000 (has links)
Este trabalho descreve a reação de reticulação alternativa do pericárdio bovino com os acetais do glutaraldeído, preparados a partir da solução de glutaraldeído na presença do etanol em meio ácido. Os acetais difundem para dentro da matriz colagênica, e a reticulação ocorre após a desproteção dos grupos aldeídicos com uma amina terciária. O material obtido sob estas condições mostrou as propriedades biológicas e mecânicas similares ou superiores àqueles descritos para o pericárdio bovino reticulado pelo procedimento convencional com glutaraldeído, e provavelmente, com resultados de uma distribuição e natureza química mais homogênea das reticulações formadas, devido à ausência das reticulações polímeros de glutaraldeído. As biopróteses manufaturadas com pericárdio reticulado com acetais do glutaraldeído, também mostraram durabilidade superior e foi menos suscetível ao processo de calcificação, como determinado em implantes subcutâneos em ratos. Resultados preliminares de teste à fadiga e performance hidrodinâmica foram caracterizados por um comportamento similar àqueles materiais tratados convencionalmente sugerindo que, o pericárdio reticulado com acetais do glutaraldeído pode ser um procedimento alternativo e mais eficiente na manufatura das biopróteses, particularmente com respeito à calcificação, um dos maiores problemas encontrados pós-implante. / This work describes the cross-linking of bovine pericardium with glutaraldehyde acetals, which are its protected forms. The acetals, prepared from a glutaraldehyde solution in the presence of ethanol in acidic media was al/owed to diffuse within the collagen matrix, and cross-linking achieved by deprotection with a tertiary amine. The material obtained under this conditions showed biological and mechanical properties similar or superior to those described for bovine pericardium crosslinked by conventional procedure with glutaraldehyde, and probably, as a results of a more homogeneous distribution and chemical nature of the formed crosslinks, that is the absence of polymeric cross-links. Bioprostheses manufactured with glutaraldehyde acetals cross-linked bovine pericardium, also showed higher durability and was less susceptible to calcification process, as determined in subcutaneous implant in rats. Preliminary results on fatigue test and hydrodynamic performance were characterized by a behavior similar to those observed for conventional/y treated materials suggesting that, glutaraldehyde acetals crosslinked bovine pericardium may be an alternate and more efficient procedure in the manufacture of bioprostheses, particularly in respect to calcification, one of the major problems found post-implantation.

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