• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 59
  • 44
  • 34
  • 13
  • 5
  • 5
  • 4
  • 4
  • 4
  • 3
  • 3
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 190
  • 50
  • 24
  • 20
  • 20
  • 20
  • 18
  • 17
  • 17
  • 16
  • 16
  • 14
  • 14
  • 14
  • 13
  • 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.
111

Apprentissage statistique pour l'intégration de données omiques / Statistical learning for omics data integration

Mariette, Jérôme 15 December 2017 (has links)
Les avancées des nouvelles techniques de séquençage ont permis de produire des données hétérogènes, volumineuse, de grande dimension et à différentes échelles du vivant. L'intégration de ces différentes données représente un défi en biologie des systèmes, défi qu'il est critique d'aborder pour tirer le meilleur parti possible de l'accumulation d'informations biologiques pour leur interprétation et leur exploitation dans un but finalisé. Cette thèse regroupe plusieurs contributions méthodologiques utiles à l'exploration simultanée de plusieurs jeux de données omiques de natures hétérogènes. Pour aborder cette question, les noyaux et les méthodes à noyaux offrent un cadre naturel, car ils permettent de prendre en compte la nature propre de chacun des tableaux de données tout en permettant leur combinaison. Toutefois, lorsque le nombre d'observations à traiter est grand, les méthodes à noyaux souffrent d'un manque d'interprétabilité et d'une grande complexité algorithmique. Une première partie de mon travail a porté sur l'adaptation de deux méthodes exploratoires à noyaux : l'analyse en composantes principales (K-PCA) et les cartes auto- organisatrices (K-SOM). Les adaptations développées portent d'une part sur le passage à l'échelle du K-SOM et de la K-PCA au domaine des omiques et d'autre part sur l'amélioration de l'interprétabilité des résultats. Dans une seconde partie, je me suis intéressé à l'apprentissage multi-noyaux pour combiner plusieurs jeux de données omiques. L'efficacité des méthodes proposées est illustrée dans le contexte de l'écologie microbienne : huit jeux de données du projet TARA oceans ont été intégrés et analysés à l'aide d'une K-PCA. / The development of high-throughput sequencing technologies has lead to produce high dimensional heterogeneous datasets at different living scales. To process such data, integrative methods have been shown to be relevant, but still remain challenging. This thesis gathers methodological contributions useful to simultaneously explore heterogeneous multi-omics datasets. To tackle this problem, kernels and kernel methods represent a natural framework because they allow to handle the own nature of each datasets while permitting their combination. However, when the number of sample to process is high, kernel methods suffer from several drawbacks: their complexity is increased and the interpretability of the model is lost. A first part of my work is focused on the adaptation of two exploratory kernel methods: the principal component analysis (K-PCA) and the self-organizing map (K-SOM). The proposed adaptations first address the scaling problem of both K-SOM and K-PCA to omics datasets and second improve the interpretability of the models. In a second part, I was interested in multiple kernel learning to combine multiple omics datasets. The proposed methods efficiency is highlighted in the domain of microbial ecology: eight TARA oceans datasets are integrated and analysed using a K-PCA.
112

Relações tritróficas: Variedades de Citros x Diaphorina citri Kuwayama, 1908 (Hemiptera: Psyllidae) x Tamarixia radiata (Waterson, 1922) (Hymenoptera: Eulophidae) / Tritrophic Relationships: Citrus varieties x Diaphorina citri Kuwayama, 1908 (Hemiptera: Psyllidae) x Tamarixia radiata (Waterson, 1922) (Hymenoptera: Eulophidae)

Gustavo Rodrigues Alves 22 January 2013 (has links)
O objetivo do presente trabalho foi avaliar a influência de variedades comerciais de citros e de murta no desenvolvimento de Diaphorina citri Kuwayama, 1908 e a preferência do parasitoide Tamarixia radiata (Waterson, 1922) sobre o referido psilídeo, criado em diferentes variedades cítricas e na murta, por meio de estudos biológicos e comportamentais, para definir estratégias de controle da praga em programas de MIP em citros. Foram realizados testes de livre escolha e confinamento (sem chance de escolha) para avaliar o efeito de variedades de citros sobre a alimentação e fertilidade de D. citri, bem como a biologia da referida espécie de psilídeo em diferentes hospedeiros. Avaliou-se ainda o efeito da variedade de citros sobre o parasitismo de T. radiata, bem como sua biologia em D. citri criado em diferentes hospedeiros. Pode-se concluir que: D. citri preferiu ovipositar e se alimentar, em teste de livre escolha, em \'Natal\', sendo que no teste de confinamento (sem chance de escolha) a oviposição foi semelhante em \'Natal\', \'Valência\' e \'Pêra\'. Em ambos os tipos de teste, \'Hamlin\' foi a menos adequada para D. citri. Com base nos demais parâmetros biológicos avaliados, a análise de agrupamento separou os hospedeiros em três grupos distintos, sendo \'Valência\' e murta os hospedeiros mais adequados ao desenvolvimento de D. citri. No segundo grupo (\'Natal\', \'Pêra\' e \'Ponkan\') concentraram-se as variedades que proporcionaram um desenvolvimento intermediário ao psilídeo, sendo \'Hamlin\' a menos adequada ao desenvolvimento do inseto. Com base na tabela de vida de fertilidade, a taxa líquida de reprodução (Ro) de D. citri foi 2,5 vezes maior quando criado em \'Valência\' em relação a \'Hamlin\'. Os demais parâmetros (T, λ e rm) também favoreceram o inseto quando criado em \'Valência\'. Os hospedeiros estudados não afetaram o parasitismo e desenvolvimento de T. radiata sobre D. citri. Os resultados obtidos poderão fornecer subsídios ao planejamento do plantio de variedades de citros em pomares novos com vistas à incidência e manejo do HLB. / This research\'s aim was to evaluate the influence of commercial citrus varieties and orange jessamine on the development of Diaphorina citri Kuwayama, 1908 and the parasitoid Tamarixia radiata (Waterson, 1922) preference on the Asian Citrus Psyllid (ACP), reared on different citrus varieties and on orange jessamine, by the means of biological and behavioral studies, in order to establish strategies of pest control in Integrated Pest Management (IPM) citrus programs. Free-choice and nochoice tests were carried out to evaluate the citrus varieties effects on the feeding and fertility of D. citri, as well as the biology of this psyllid species on different hosts. It was evaluated the citrus variety effect on the T. radiata parasitization, as well as its biology with D. citri reared on different hosts. It can be concluded that: D. citri preferred laying eggs and feeding, in free-choice tests, on \'Natal\', while in the nochoice test, the laying-eggs behavior was the same on \'Natal\', \'Valência\' and \'Pêra\'. In the both tests, \'Hamlin\' was the least suitable for D. citri. According to the other biological characteristics evaluated, the grouping analysis identified 3 different groups, being \'Valência\' and orange jessamine the best hosts for D. citri development. In the second group (\'Natal\', \'Pêra\' e \'Ponkan\') are the varieties that provided a reasonable development to the psyllid, being \'Hamlin\' the least suitable for the insect development. According to the fertility life table, the reproduction net rate (Ro) of D. citri was 2,5 times bigger if reared on \'Valência\' compared to \'Hamlin\'. The other life table parameters (T, λ e rm) also supported the results when it was reared on \'Valência\'. The studied hosts did not affect the parasitization and the development of T. radiata on D. citri. The results obtained will provide information for planting planning of citrus varieties in new groves considering the HLB incidence and management.
113

Rozvojové aspekty liberalizace obchodu na příkladu vývoje vztahů EU se zeměmi AKT / Developement Aspects of Trade Liberalization : EU-ACP Relations

Svoboda, Štěpán January 2009 (has links)
The thesis deals with the trade liberalization among unequally developed partners and its development issues. At global level it refers to WTO development agenda, however, at regional level it focuses on north-south trade agreements, particularly on EU-ACP relations. The aim of the thesis is to analyze these relations and the way and scope of how they have contributed to economic growth and welfare of ACP states considering both static and dynamic effects. It also evaluates opportunities and threads of Economic Partnership Agreements.
114

Spectroscopie et imagerie Raman de matériaux inhomogènes / Spectroscopy and Raman imaging of inhomogeneous materials

Maslova, Olga A. 20 October 2014 (has links)
L’objet de cette thèse consiste en des développements de méthodes en spectroscopie et imagerie Raman. Après une revue des outils statistiques permettant de traiter de gros volumes de données (analyse multivariée, classification), l’étude est appliquée à deux familles de matériaux déjà bien connus, utilisés comme modèles pour tester les limites des développements mis en oeuvre. La première famille est une série de matériaux carbonés, traités à différentes températures, avec des inhomogénéités à l’échelle du nm, dont la taille est déduite d’une approche conjointe Raman-diffraction des rayons X. Un autre résultat concerne l’effet du polissage, qui induit des artefacts Raman conduisant à surestimer le désordre structural local, et une méthode basée sur la largeur de la bande G est proposée. L’autre classe de matériaux présente cette fois des inhomogénéités à des échelles supérieures au micromètre, il s’agit de céramiques d’oxyde d’uranium appauvri. L’imagerie Raman, particulièrement bien adaptée en termes d’échelle spatiale, est utilisée pour sonder les surfaces obtenues, Le traitement des données est effectué par un approche mêlant analyse multivariée (analyse en composantes principales), et ajustement classique par Lorentziennes. L’interprétation des données obtenues est soutenue par une analyse par electron backscattering diffraction (EBSD), permettant de séparer l’effet d’orientation des grains de céramiques, d’autres effets sous-jacents. Ceux-ci, principalement localisés aux joints de grains, avec l’existence d’un mode Raman caractéristique, paraissent liés à des variations de stoechiométrie en oxygène ou d’impuretés, ou à des inhomogénéités de contrainte. Les perspectives de ce travail portent notamment sur la mise en oeuvre d’autres méthodes mathématiques, et pour l’aspect matériaux, sur l’analyse fine d’endommagements par irradiation des UO2, (effets d’anisotropie, rôle des joints de grains. / This thesis is aimed at developing methodologies in Raman spectroscopy and imaging. After reviewing the statistical instruments which allow treating giant amount of data (multivariate analysis and classification), the study is applied to two families of well-known materials which are used as models for testing the limits of the implemented developments. The first family is a series of carbon materials pyrolyzed at various temperatures and exhibiting inhomogeneities at a nm scale which is suitable for Raman--X-ray diffraction combination. Another results concern the polishing effect on carbon structure. Since it is found to induce Raman artifacts leading to the overestimation of the local structural disorder, a method based on the use of the G band width is therefore proposed in order to evaluate the crystallite size in both unpolished and polished nanographites. The second class of materials presents inhomogeneities at higher (micrometric) scales by the example of uranium dioxide ceramics. Being well adapted in terms of spatial scale, Raman imaging is thus used for probing their surfaces. Data processing is implemented via an approach combining the multivariate (principal component) analysis and the classical fitting procedure with Lorentzian profiles. The interpretation of results is supported via electron backscattering diffraction (EBSD) analysis which enables us to distinguish the orientation effects of ceramic grains from other underlying contributions. The last ones are mainly localized at the grain boundaries, that is testified by the appearance of a specific Raman mode. Their origin seems to be caused by stoichiometric oxygen variations or impurities, as well as strain inhomogeneities. The perspectives of this work include both the implementation of other mathematical methods and in-depth analysis of UO2 structure damaged by irradiation (anisotropic effects, role of grain boundaries).
115

EU-ACP economic agreements and WTO/GATT compatibility : options for ACP countries under Cotonou Agreement

Ojiambo, Colbert 04 October 2010 (has links)
The member states of European Union (EU) and a group of African, Caribbean and Pacific (ACP) states are currently negotiating for new trading agreements compatible with World Trade Organization‘s (WTO) rules. Whereas both the EU and the ACP states are in agreement that the new trading arrangements must be WTO compatible, there is no consensus on the format of the new trading agreements. The EU has insisted that the new trading arrangements should be in the form of free trade agreements, established under Article XXIV of General Agreement on Tariffs and Trade (GATT). Unlike the previous EU – ACP trade agreements which were non – reciprocal, Article XXIV requires that the new trading agreements should be reciprocal. Consequently the EU has gone ahead to negotiate for reciprocal Economic Partnership Agreements (EPAs) with some of the ACP states. Some ACP countries which are opposed to reciprocity have proposed that the new trading arrangements should be established under the provisions of Enabling Clause. Others have suggested that EU should attempt to apply for a WTO waiver. The Cotonou Agreement, under which the new trading agreements are being negotiated, provides that in case of those countries which are not ready to negotiate for EPAs, the EU should examine alternative possibilities, in order to provide these countries with a new framework for trade which is equivalent to their existing situation and in conformity with WTO rules. So far no alternative trading arrangements have been proposed. Although some ACP countries have agreed to negotiate for Economic Partnership Agreements under article XXIV of GAAT, there is no consensus on the interpretation of key provisions of Article XXIV. Under Article XXIV, the parties are required to remove substantially all trade barriers between themselves within reasonable time. The meaning of the phrases 'substantially all' and 'reasonable time‘ has remained controversial with each party giving an interpretation that favours its interests. Lack of consensus on the meaning of these phrases has hindered the conclusion of negotiations for EPAs. In a nutshell, the question of WTO compatibility presents the biggest hurdle to the conclusion of the new trading arrangements between the EU and the ACP group. This paper is an evaluation of the options available to the ACP countries to conclude WTO compatible trading arrangements with the EU. Chapter one of this paper is an introductory chapter which offers an overview of the entire paper. Chapter two sets out in details the historical background of the economic relationship between the EU and the ACP states. This chapter illustrates the historical background from which the new trading agreements have evolved to help the reader understand certain key features of the current economic partnership agreements. Chapter three looks at the GATT/WTO provisions relevant to the establishment of WTO compatible trading arrangements between EU and ACP countries. Particular emphasis is placed on Article XXIV, the Enabling Clause and the WTO waiver. Chapter four is the main chapter in which the paper explores the possibilities of concluding WTO compatible trading agreements under Article XXIV, Enabling clause and the WTO waiver. Chapter five draws the conclusions of this paper. / Dissertation (LLM)--University of Pretoria, 2010. / Centre for Human Rights / unrestricted
116

[pt] ANÁLISE MULTIELEMENTAR COMO FERRAMENTA PARA A DIFERENCIAÇÃO ENTRE MARCAS DE CIGARROS COMERCIALIZADAS NO BRASIL / [en] MULTI-ELEMENT ANALYSIS AS A TOOL FOR DIFFERENTIATING BETWEEN CIGARETTE BRANDS SOLD IN BRAZIL

LUCAS SOARES RODRIGUES 03 October 2022 (has links)
[pt] A presença de metais-traço nos cigarros oferece uma fonte de informação potencial do ponto de vista forense e criminológico, na determinação e classificação de marcas de tabaco, com o intuito de diferenciar as marcas legalizadas das contrabandeadas. Por isso, neste trabalho, almejou-se desenvolver e validar métodos para determinação metais e semimetais presentes nos cigarros, com o intuito de avaliar a viabilidade de discriminação entre as diferentes marcas, analisando as amostras após o processo de calcinação e dissolução ácida. Estes métodos englobam as análises químicas por técnicas espectrométricas (CV-AAS, ICP-OES e DRC-ICP-MS) e posterior interpretação de dados por ACP (Análise dos Componentes Principais) e AAH (Análise de Agrupamento Hierárquico). As concentrações de metais e semimetais (As, Ba, B, Cd, Co, Cu, Fe, Mn, Hg, Ni, Sr e Zn) foram estudadas para dez diferentes marcas de cigarros, obtidas em tabacarias e lojas locais, representando as marcas mais consumidas no país. A utilização da ACP indicou a presença de quatro componentes principais que, em conjunto, explicavam mais de 80 por cento da variabilidade dos dados amostrais. Esses resultados comprovaram a existência de diferenças significativas entre as marcas de tabaco em seus conteúdos elementares, possibilitando a diferenciação entre marcas ilegais e marcas legalizadas e o agrupamento das marcas legalizadas de acordo com as empresas de tabaco as quais pertencem, sendo corroborado pela AAH, feita pelo método da distância média de ligação (UPGMA). Os teores de umidade, cinzas totais e pH de cada marca também foram determinados, no entanto não contribuíram efetivamente para a diferenciação entre as marcas estudadas. A AAH foi utilizada para a interpretação de possíveis similaridades entre os elementos, e em conjunto com o teste de correlação linear de Pearson, indicou similaridades entre os elementos Ba e Sr . Agrupamentos entre Fe e Zn com o Sr e Co com o Mn também foram detectados. / [en] The presence of trace metals in cigarettes offers potential source of information from a forensic and criminological point of view, which deals with the determination and classification of tobacco brands, with the aim of differentiating legal brands from smuggled brands. Therefore, this work aimed to develop and validate methods for determining the metallic content present in cigarettes, in order to assess the feasibility of discrimination between different brands, analyzing cigarettes after the process of calcination and acid digestion. These methods include chemical analysis by spectrometric techniques (CV-AAS, ICP-OES and DRC-ICPMS) and subsequent data interpretation by PCA (Principal Component Analysis) and HCA (Hierarchical Cluster Analysis). The concentration of metals and semimetals (As, Ba, B, Cd, Co, Cu, Fe, Mn, Hg Ni, Sr and Zn) were studied for ten different brands of cigarettes, obtained in tobacconists and local stores, representing the brands most consumed in the country. The analysis of PCA indicated the presence of four principal components that together explained more than 80 percent of the variability of the sample data. These results proved the existence of significant differences between tobacco brands in their elemental content, allowing the differentiation between illegal brands and legalized brands and the grouping of legal brands according to the tobacco companies to which they belong, being corroborated by the HCA performed by the average link distance method (UPGMA). The moisture content, total ash and pH of each brand were also determined, however they did not contribute effectively to the differentiation between the brands studied. The HCA used for the interpretation of possible similarities between the elements, and interpreted together with Pearson s linear correlation test indicated similarities between the elements Ba, Sr, in addition to indicating the proximity between the Mn and the Cd. Clusters between Fe and Zn with Sr and Co with Mn were also detected.
117

EPA’s & Problematizing Development: Discourse, Design, Values

Olausson, Justine January 2009 (has links)
This thesis investigates and problematizes the notion of development in the context of the EU-ACP EPA agreements with a particular focus on Kenya. Official statements, documents, empirical observation and qualitative interviews conducted in Nairobi and Kagwe, Kenya in April of 2009 provide empirical data. Applying the concepts of international trade theory, capacity developments complex adaptive systems approach and supplementing these concepts with an underlying thread of axiology, this paper seeks to explore the drastically divided and widely differing definitions of the situation, world views and casual beliefs in viewing the EPA development tool for what it is vs. what it means. By problematizing the notion of development, the findings suggest that it seems as though much of the dissonance between what constitutes development, what the ‘problem’ is, why it exists, and what the ‘solution’ is, is the result of a clash between theoretical models and the informal concepts of how things get done in a particular context. Thus, it is difficult seeing the EPAs functioning as a tool for a form of development that would suit the values, norms, and voices involved in conceptualizing development.
118

Portál univerzálního protokolu řízení přístupu / Portal of the universal access control protocol

Čepelák, Tomáš January 2014 (has links)
The paper focuses on the issue of access control. It presents an universal bilateral protocol of access control of ACP. The paper describes the messages and its sequences that AC portals uses for communication. It describes the functions and features of the modules from which the portal is composed. The paper suggests the concept of a modular AC portal solutions including the design of basic modules. It also outlines possible test scenarios. Under this proposal is generated functional AC portal on the .NET Framework platform using the C\# programming language. The portal provides access to local assets or to the assets on other computers in the local network. Created application is tested according to the scenarios proposed in both the network version and the local version of the AC portal. Test results are objectively evaluated and commented.
119

L'accord de Cotonou et les contradictions du droit international : l'intégration des règles de l'Organisation mondiale du commerce et des droits humains dans la coopération ACP-CE

Gallie, Martin January 2006 (has links)
"Thèse présentée à la Faculté des études supérieures de l'Université de Montréal en vue de l'obtention du grade de Docteur en Droit (LL.D.) Et à A la faculté de droit Jean Monnet en vue de l'obtention du doctorat en Sciences Juridiques" / Ce travail poursuit deux objectifs principaux: un objectif juridique et un objectif d'ordre épistémologique. Il s'agit tout d'abord de rendre compte d'un point de vue juridique et empirique les implications du passage des Conventions de Lomé à l'Accord de Cotonou. Nous examinons les implications de la redéfinition des accords de coopération sur les politiques de développement des Etats ACP, et plus précisément l'évolution des obligations à la charge des deux groupes de pays dans les domaines du commerce international et des droits humains. Dans un premier temps, nous montrons que la non réciprocité des obligations commerciales entre les deux groupes de pays qui caractérisait les Conventions de Lomé est définitivement écartée au profit d'obligations réciproques et identiques pour les deux groupes de pays en conformité des dispositions de l'Organisation mondiale du commerce. Le principe de l'inégalité compensatrice est abandonné au profit de la libéralisation commerciale. Le traitement spécial et différencié, pourtant consacré dans l'Accord instituant l'OMC, apparaît ainsi dépourvu d'une grande partie de son intérêt. Dans un deuxième temps, ce sont les obligations relatives au respect des droits humains qui retiennent notre attention. L'élargissement du champ de la coopération à des questions considérées depuis l'indépendance comme des questions relevant de la compétence interne des Etats, se traduit par une remise en cause de la souveraineté des Etats ACP. Le principe de non-ingérence dans les affaires intérieures, héritage de la décolonisation, est ainsi remis en question. Mais surtout, nous établissons que tous les droits humains ne sont pas concernés par cet élargissement. Le deuxième objectif de ce travail est d'ordre épistémologique. Il VIse à démontrer le caractère heuristique d'une analyse constructiviste du droit pour la compréhension de notre objet mais aussi l'intérêt de ce type d'approche au regard des débats qui structurent le champ disciplinaire sur les rapports entre les droits humains et le droit du commerce international. A travers l'étude de l'Accord de Cotonou, nous tentons de mettre en lumière le fait que les droits humains et règles de l'OMC n'évoluent ni de manière complémentaire ni séparément et qu'il ne suffit pas de raisonner en termes de «rattrapage» et de correctifs ponctuels afin d'harmoniser ces deux champs de règles. En conclusion nous constatons que cinq ans ont suffi aux institutions européennes pour réaliser un véritable «exploit» politique. Elles ont réussi à renverser l'ensemble des obligations économiques qui étaient à la charge des deux groupes de pays, à supprimer les protocoles produits en faveur des ACP, à faire adopter un programme de libéralisation commercial qui va au-delà de tout ce qui a été négocié jusqu'ici au niveau multilatéral et ce, sous couvert de mise en conformité avec les dispositions de l'ÜMC. Enfin, l'DE a fragilisé le Groupe ACP en le morcelant en six régions, dont certaines n'ont aucune existence institutionnelle, avec lesquelles elle négocie actuellement un vaste programme de libéralisation commerciale. En ce qui a trait au respect des droits humains on constate qu'à la différence des normes de l'OMC qui font l'objet de négociations permanentes et structurent le cadre institutionnel et le fond de la coopération, le respect des droits humains ne fait pas ou peu l'objet de négociations entre les deux groupes de pays. De plus, s'ils occupent désormais une place centrale dans le discours des institutions communautaires en charge du développement, le seul mécanisme mis en oeuvre pour sanctionner leurs violations est utilisé d'une manière partiale et sélective. Seule l'DE peut l'utiliser et elle ne choisit de le faire que quand la sanction infligée à un pays ACP ne met pas en péril ses propres intérêts. Bref, l'intégration des droits humains dans le cadre de la coopération contribue davantage aujourd'hui à une remise en cause de l'égalité souveraine des Etats qu'à la promotion des Pactes de 1966, au respect des normes de l'OIT ou du droit des réfugiés. / This work pursues two aims. The first one is to seek to understand and to explain the stakes and the implications of the transformation of the Lomé convention into the Cotonou agreement, from a constructive approach of law. It is then a question of contributing to the legal thought concerning the degree of complimentary and coherence between the two fields of the internationallaw, human rights and international trade law. The second aim led us to look into the question of the real integration, which proved to be selective, of the standards coming from these two fields of law into the Cotonou Agreement. In the cooperation, the breach of human rights, as the OMC standards, is appreciated in a subjective and unilateral way by the E.U. Far from contributing to a complementary approach, the cooperation reinforces the dichotomy between these two fields of internationallaw, by treating them on a hierarchical basis.
120

Développement d'algorithmes temps réel de traitement de séquences d'images animées biomédicales pour la thermothérapie guidée par IRM

Maclair, Grégory 05 December 2008 (has links)
L'hyperthermie locale guidée par IRM s'est développée en pratique clinique au cours des dernières années. Le principe repose sur la destruction des cellules tumorales grâce à une élévation de température pendant une durée suffisante. L'acquisition d'images IRM simultanément au chauffage permet un monitorage en ligne de la température et un contrôle de la destruction cellulaire induite par l'hyperthermie appliquée aux tissus.Le principal objectif de cette thèse est de mettre en oeuvre des stratégies permettant de corriger les artefacts induits par la respiration ou le battement cardiaque pour les organes mobiles (foie, rein, coeur) et pour les organes non-mobiles (seins). La contribution principale de ce travail de thèse consiste à proposer une méthode de modélisation des champs de déplacements à l'aide d'une Analyse en Composantes Principales (ACP) en s'appuyant sur le caractère périodique des phénomènes physiologiques observés. / During the last years MR-guided lo cal hyp erthermia has b een develop edfor the clinical practice. Hyp erthermia is based on the destruction of tumorcells due to an increased temp erature over a sufficient amount of time. The si-multaneous acquisition of MR images during the heating pro cess allows on-linemonitoring of the temp erature and a control of the tissue destruction inducedby the hyp erthermia treatment. The on-line calculation of the temp erature isnot a trivial problem. This is b ecause the physical and physiological pheno-mena like the respiration disturb the temp erature measurement. Hence, it isnecessary to develop strategies for real-time correction in order to deliver pre-cise temp erature maps. In this work, we prop ose several algorithms for imagetreatment enabling the correction of artefacts related to motion and magneticsusceptibility effects. These corrections will provide a reliable estimation of theefficiency of the hyp erthermia treatment.

Page generated in 0.0347 seconds