Les lésions de la moelle épinière ont un impact significatif sur la qualité de la vie car elles peuvent induire des déficits moteurs (paralysie) et sensoriels. Ces déficits évoluent dans le temps à mesure que le système nerveux central se réorganise, en impliquant des mécanismes physiologiques et neurochimiques encore mal connus. L'ampleur de ces déficits ainsi que le processus de réhabilitation dépendent fortement des voies anatomiques qui ont été altérées dans la moelle épinière. Il est donc crucial de pouvoir attester l'intégrité de la matière blanche après une lésion spinale et évaluer quantitativement l'état fonctionnel des neurones spinaux. Un grand intérêt de l'imagerie par résonance magnétique (IRM) est qu'elle permet d'imager de façon non invasive les propriétés fonctionnelles et anatomiques du système nerveux central. Le premier objectif de ce projet de thèse a été de développer l'IRM de diffusion afin d'évaluer l'intégrité des axones de la matière blanche après une lésion médullaire. Le deuxième objectif a été d'évaluer dans quelle mesure l'IRM fonctionnelle permet de mesurer l'activité des neurones de la moelle épinière. Bien que largement appliquées au cerveau, l'IRM de diffusion et l'IRM fonctionnelle de la moelle épinière sont plus problématiques. Les difficultés associées à l'IRM de la moelle épinière relèvent de sa fine géométrie (environ 1 cm de diamètre chez l'humain), de la présence de mouvements d'origine physiologique (cardiaques et respiratoires) et de la présence d'artefacts de susceptibilité magnétique induits par les inhomogénéités de champ, notamment au niveau des disques intervertébraux et des poumons. L'objectif principal de cette thèse a donc été de développer des méthodes permettant de contourner ces difficultés. Ce développement a notamment reposé sur l'optimisation des paramètres d'acquisition d'images anatomiques, d'images pondérées en diffusion et de données fonctionnelles chez le chat et chez l'humain sur un IRM à 3 Tesla. En outre, diverses stratégies ont été étudiées afin de corriger les distorsions d'images induites par les artefacts de susceptibilité magnétique, et une étude a été menée sur la sensibilité et la spécificité de l'IRM fonctionnelle de la moelle épinière. Les résultats de ces études démontrent la faisabilité d'acquérir des images pondérées en diffusion de haute qualité, et d'évaluer l'intégrité de voies spinales spécifiques après lésion complète et partielle. De plus, l'activité des neurones spinaux a pu être détectée par IRM fonctionnelle chez des chats anesthésiés. Bien qu'encourageants, ces résultats mettent en lumière la nécessité de développer davantage ces nouvelles techniques. L'existence d'un outil de neuroimagerie fiable et robuste, capable de confirmer les paramètres cliniques, permettrait d'améliorer le diagnostic et le pronostic chez les patients atteints de lésions médullaires. Un des enjeux majeurs serait de suivre et de valider l'effet de diverses stratégies thérapeutiques. De telles outils représentent un espoir immense pour nombre de personnes souffrant de traumatismes et de maladies neurodégénératives telles que les lésions de la moelle épinière, les tumeurs spinales, la sclérose en plaques et la sclérose latérale amyotrophique. / Spinal cord injury has a significant impact on quality of life since it can lead to motor (paralysis) and sensory deficits. These deficits evolve in time as reorganisation of the central nervous system occurs, involving physiological and neurochemical mechanisms that are still not fully understood. Given that both the severity of the deficit and the successful rehabilitation process depend on the anatomical pathways that have been altered in the spinal cord, it may be of great interest to assess white matter integrity after a spinal lesion and to evaluate quantitatively the functional state of spinal neurons. The great potential of magnetic resonance imaging (MRI) lies in its ability to investigate both anatomical and functional properties of the central nervous system non invasively. To address the problem of spinal cord injury, this project aimed to evaluate the benefits of diffusion-weighted MRI to assess the integrity of white matter axons that remain after spinal cord injury. The second objective was to evaluate to what extent functional MRI can measure the activity of neurons in the spinal cord. Although widely applied to the brain, diffusion-weighted MRI and functional MRI of the spinal cord are not straightforward. Various issues arise from the small cross-section width of the cord, the presence of cardiac and respiratory motions, and from magnetic field inhomogeneities in the spinal region. The main purpose of the present thesis was therefore to develop methodologies to circumvent these issues. This development notably focused on the optimization of acquisition parameters to image anatomical, diffusion-weighted and functional data in cats and humans at 3T using standard coils and pulse sequences. Moreover, various strategies to correct for susceptibility-induced distortions were investigated and the sensitivity and specificity in spinal cord functional MRI was studied. As a result, acquisition of high spatial and angular diffusion-weighted images and evaluation of the integrity of specific spinal pathways following spinal cord injury was achieved. Moreover, functional activations in the spinal cord of anaesthetized cats was detected. Although encouraging, these results highlight the need for further technical and methodological development in the near-future. Being able to develop a reliable neuroimaging tool for confirming clinical parameters would improve diagnostic and prognosis. It would also enable to monitor the effect of various therapeutic strategies. This would certainly bring hope to a large number of people suffering from trauma and neurodegenerative diseases such as spinal cord injury, tumours, multiple sclerosis and amyotrophic lateral sclerosis.

Women exhibit greater habituation to painful stimuli than men. The neural mechanism underlying this sex difference is unknown. However, pain habituation has been associated with pain-evoked activity of the subgenual anterior cingulate cortex (sgACC), implicating a connection between the sgACC and the descending pain antinociceptive system. Therefore, the thesis hypothesis was that women have stronger connectivity than men between the sgACC and the descending antinociceptive system. Healthy subjects provided informed consent. 3T MRI images included anatomical diffusion-weighted imaging for structural connectivity analyses (SC) with probabilistic tractography and resting-state functional images for functional connectivity (FC) analyses. Women had stronger sgACC FC with nodes of the descending pain modulation system (raphe, PAG) and the medial thalamus. In contrast, men had stronger sgACC FC with nodes of the salience/attention network (anterior insula, TPJ) and stronger sgACC SC with the hypothalamus. These findings implicate a mechanism for pain habituation and its associated sex differences.

Women exhibit greater habituation to painful stimuli than men. The neural mechanism underlying this sex difference is unknown. However, pain habituation has been associated with pain-evoked activity of the subgenual anterior cingulate cortex (sgACC), implicating a connection between the sgACC and the descending pain antinociceptive system. Therefore, the thesis hypothesis was that women have stronger connectivity than men between the sgACC and the descending antinociceptive system. Healthy subjects provided informed consent. 3T MRI images included anatomical diffusion-weighted imaging for structural connectivity analyses (SC) with probabilistic tractography and resting-state functional images for functional connectivity (FC) analyses. Women had stronger sgACC FC with nodes of the descending pain modulation system (raphe, PAG) and the medial thalamus. In contrast, men had stronger sgACC FC with nodes of the salience/attention network (anterior insula, TPJ) and stronger sgACC SC with the hypothalamus. These findings implicate a mechanism for pain habituation and its associated sex differences.

Diffusion Tensor Imaging (DTI) is a well-established magnetic resonance technique that can non-invasively interpret tissue geometry and track neural pathways by sampling the diffusion of water molecules in the brain tissue. However, it is currently limited to tracking large nerve fiber bundles and fails to faithfully resolve thinner fibers. Conventional DTI studies use a diffusion time, t[subscript diff] of 30 ms - 55 ms for diffusion measurements. This work proposes the use of DTI at long t[subscript diff] to enhance the sensitivity of the method towards regions of low diffusion anisotropy and improve tracking of smaller fibers. The Stimulated Echo Acquisition Mode (STEAM) sequence was modified to allow DTI measurements at long t[subscript diff] (approximately 200 ms), while avoiding T2 signal loss. For comparison, DTI data was acquired using STEAM at the shorter value of t[subscript diff] and with the standard Double Spin Echo sequence with matched signal-to-noise ratio. This approach was tested on phantoms and fixed monkey brains and then translated to in vivo studies in rhesus macaques. Qualitative and quantitative comparison of the techniques was based on fractional anisotropy, diffusivity, three-phase plots and directional entropy. Tensor-field maps and probabilistic connectivity fronts were evaluated for all three acquisitions. Comparison of the tracked nerve pathways showed that fibers obtained at long t[subscript diff] were much longer. Further, the optic tract was tracked in ex vivo fixed rhesus brains for cross validation. The optic tract, traced at long t[subscript diff], conformed to the well documented anatomical description, thus confirming the accuracy of tract tracing at long t[subscript diff]. The benefits of DTI at long t[subscript diff] indeed help to realize the potential of tensor based tractography towards studying neural development and diagnosing neuro-pathologies, albeit the improvement is more significant ex vivo than in vivo.

Introduction Optimal nutrition is vital in the management of infants born preterm. Dietary fat in infancy is fundamental for the provision of energy for growth and development. Essential fatty acids, specifically Long Chain Polyunsaturated Fatty Acids (LC-PUFAs) such as docosahexaenoic acid (DHA), have been under investigation by several international research groups in the past decade. Essential fatty acids are critical in neurodevelopment as DHA is found in high proportions in structural lipids of cell membranes, particularly in the central nervous system (CNS). The accumulation of essential fatty acids and particularly DHA in the brain and retina occurs most rapidly during the perinatal period, therefore preterm infants are of particular concern (Singer, 2001). Current scientific consensus is that the optimum growth rate for preterm infants is equal to the in utero growth rate throughout the last trimester, however, failure to achieve the optimum intrauterine growth rate is common in preterm infants (Olhager and Forsum, 2003). Preterm infants require large amounts of energy and nutrients with which many infants are not provided or are not able to absorb, due to immature gastrointestinal and metabolic systems and other medical complications (Olhager and Forsum, 2003). There are a number of unresolved issues regarding optimal growth rate and total energy requirements (ER) for preterm infants. Hypotheses/Objectives This study is a “side study” to a double blind randomised controlled trial (RCT) of DHA supplementation in preterm infants. The hypothesis of this “side study” is that increased DHA during the neonatal period would increase total energy expenditure (TEE) and improve neurodevelopmental outcome. Specifically, at term postconceptual age (PCA) it was hypothesised that preterm infants receiving higher intake of DHA would have higher TEE’s due to the acceleration in brain maturation. Also, it was hypothesised that preterm infants receiving high levels of DHA would have TEE’s equivalent to term born infants due to their same brain maturation status. Other hypothesised effects of DHA supplementation include an accelerated maturation of the visual cortical pathways, and accelerated white matter (WM) tract development aiding in brain maturation. The first objective of this study was to measure TEE and ER in very preterm infants when they reached an age of 31-33 weeks post conceptional age (PCA). The effects of DHA supplementation on TEE, at simulated in utero levels, in very preterm infants (born < 33 weeks PCA), when assessed at term equivalent (40 weeks PCA) were studied. Another objective was to compare WM brain tissue volume at term PCA between two preterm groups and then with the term born infants. Visual latency was also compared between the two preterm infant groups and then with the term born infants. Methods TEE was measured using the doubly labelled water (DLW) method which is based on the differential elimination of 2H (deuterium) and 18O from the body subsequent to a loading dose of these isotopes. TEE was measured at the preterm age between 31-33 weeks PCA and again at term PCA. TEE measurements are made at term PCA in a term born control group. Brain assessment was by Magnetic Resonance Imaging and (MRI) and Visual Evoked Potential (VEP). Magnetic resonance imaging quantitatively measured brain volumes and WM. Visual evoked potential would provide information on visual latency and amplitude. Results The cohort consisted of 38 infants. The TEE of the very preterm infant group was measured at 31-33 weeks PCA. The mean (±standard deviation) (SD) TEE was calculated at 80(±27) kcal/kg/d, and using data in the literature for foetal energy accretion of 28kcal/kg/d, the mean ER was calculated to be 108(±27) kcal/kg/d. At term PCA TEE was calculated for the preterm DHA supplemented group to be 56(±19) kcal/kg/d and for the non-DHA supplemented group 70(±39) kcal/kg/d. These measurements were not statistically different. Flash VEP conducted on preterm given different amounts of DHA tested at term PCA found no statistically different measurements. When combining these results and comparing them to measurements of term born infants at term PCA, the right eye measurements showed that preterm infants had statistically greater latencies than term infants. When combining the left and right eye measurements the latencies no statistical significance was found. Amplitude was also not statistically significant between the groups. MRI measures at term PCA were not statistically different DHA supplemented and the non-DHA supplemented preterm infant group. When the preterm infant cohort was combined and compared to the term born infant group, the results showed that preterm infants imaged at term PCA had reduced WM development in a number of frontal lobe projections, and anterior and posterior commissarial pathways of the corpus callosum and corona radiata. Discussion The TEE and ER measurements in this study represent the largest preterm infant cohort to date. The ER values reported here are of value in allowing the calculation of appropriate feeding and nutritional strategies for preterm infants. Although no differences in TEE between the DHA and non DHA supplemented groups were found this may have been due to the small sample size. With regard to the latency outcomes, it can be speculated that if measurements were conducted at a later PCA the correlations may have been stronger and significant. Several other factors may have also affected the results, including alertness of the infant at the time of testing, thickness of the cranium, and other health factors could not be controlled for. This study contains the youngest cohort to be compared via Flash VEP. The MRI data did not find significant differences in brain volume and WM between the DHA supplemented and the non-DHA supplemented groups. The infant CNS is rapidly developing and there are multiple environmental factors which may have affected outcomes. The data did however find differences in WM development between the preterm and term infants. The reduced WM development found in the preterm infants compared to term born infants may provide some explanation for the correlation between preterm birth and poorer cognitive and functional outcomes. Larger studies which extend beyond the first months of life are recommended in order to investigate the long-term relationships between DHA supplementation, TEE and brain maturation.

No description available.

INTRODUÇÃO: Epilepsia do lobo temporal mesial (ELTM) por esclerose hipocampal (EH) é a forma de epilepsia focal mais comum na idade adulta e a causa mais frequente de refratariedade ao tratamento clínico. Apesar de se tratar de uma patologia da substância cinzenta, alguns estudos, por meio da imagem por tensor de difusão (diffusion tensor imaging-DTI), têm demonstrado alteração da substância branca temporal e extratemporal nestes pacientes. O corpo caloso (CC) é a maior comissura cerebral conectando áreas corticais homólogas de ambos os hemisférios cerebrais e tem sido implicado na propagação da atividade epiléptica. O objetivo principal do presente estudo foi avaliar possíveis alterações no CC de pacientes com ELTM-EH pela técnica de DTI e verificar se essas dependem da lateralidade da EH e da concordância entre os exames de ressonância magnética (RM) e os exames de vídeo-eletroencefalograma (EEG). Como objetivo secundário, também avaliou-se se estas alterações se correlacionavam com alguma variável clínica ou com as medidas volumétricas do CC. MÉTODOS: 42 pacientes com ELTM-EH (idades: 20-54 anos) e 30 voluntários saudáveis como grupo controle (idades: 18-53 anos) realizaram exame de RM de crânio, sendo obtidas sequências de DTI com 32 direções de gradiente e imagens volumétricas ponderadas em T1. Os pacientes foram também divididos em subgrupos: EH à direita e EH à esquerda, e em pacientes concordantes e discordantes. Os valores de anisotropia fracionada (AF), difusividade média (DM), difusividade axial (DA), difusividade radial (DR) e os dados volumétricos foram extraídos a partir de cinco segmentos obtidos automaticamente na secção sagital do CC. Foram realizadas comparações dos parâmetros de DTI no CC entre os grupos de pacientes e controles, e entre os subgrupos de pacientes. Foram investigadas correlações entre os parâmetros do tensor de difusão e as variáveis clínicas. As alterações volumétricas no CC dos pacientes com ELTM-EH bem como a correlação dessas alterações com as anormalidades de difusão também foram avaliadas. Considerou-se um valor de p < 0,05 como estatisticamente significativo. RESULTADOS: Nas regiões anterior, médio-posterior e posterior do CC dos pacientes, observaram-se redução da AF e aumento da DM e da DR, em relação aos controles. A DA manteve-se inalterada. Não foram demonstradas diferenças nos padrões de alteração de difusão entre os pacientes com EH à direita e com EH à esquerda, nem entre pacientes concordantes e discordantes. Não foram observadas correlações significativas entre os parâmetros do tensor de difusão com a idade ao evento inicial, idade de início da epilepsia, tempo de doença, tempo de epilepsia, período de latência e frequência de crises. No entanto, pacientes que apresentaram crise febril como evento precipitante inicial exibiram maior intensidade e extensão das alterações de difusão. Observou-se redução volumétrica difusa do CC, sendo demonstrada correlação negativa significativa entre DM e DR, e o volume nos segmentos central, médio-posterior e posterior, e, ainda, entre DA e volume do segmento posterior. Nós observamos, ainda, correlação negativa significativa entre o volume e o tempo de epilepsia, e o tempo de doença. CONCLUSÕES: Houve alteração dos parâmetros de DTI em áreas específicas do CC e redução volumétrica difusa desta estrutura. Tais anormalidades parecem ser secundárias à propagação das crises epilépticas ao longo de vias específicas anatômica ou funcionalmente relacionadas aos lobos temporais promovendo alterações secundárias na substância branca cerebral. O histórico de crise febril está relacionado a maior intensidade e extensão de acometimento do CC / INTRODUCTION: Mesial temporal lobe epilepsy (MTLE) with hippocampal sclerosis (HS) is the most common form of focal epilepsy in adults and it is frequently associated with refractoriness to medical treatment. Although epilepsy is considered a grey-matter disease, abnormalities in the temporal and extra-temporal white matter have been identified in these patients with diffusion tensor imaging (DTI). The corpus callosum (CC) is the major white matter tract connecting both cerebral hemispheres and has been implicated as an important route of spread of epileptic activity. The first goal of this study was to detect DTI abnormalities in specific areas of the CC in patients with MTLE-HS and to verify if these abnormalities depend on the laterality of the HS and on the concordance between the magnetic resonance imaging (MRI) and video-electroencephalogram (EEG). As a second goal we assessed if DTI results were correlated with any clinical variable or volumetric changes of the CC. METHODS: 42 patients (age: 20-54 years) and 30 healthy controls (age:18-53 years) were submitted to brain MRI. DTI sequences with 32 gradient encoding directions and volumetric T1-weighted images were obtained. Additionally, we grouped the patients in left sided and right sided HS and in concordant and discordant HS. Mean values of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD) and volumetric results were extracted from five segments at the midsagittal section of the CC obtained through automatic segmentation. Comparisons of DTI parameters of the CC were performed between patients and controls and between subgroups of patients. Correlations between DTI parameters and clinical findings were calculated. We also evaluated volume abnormalities of the CC in MTLE-HS patients and the correlations between these abnormalities and DTI changes. We considered a value of p <0.05 statistically significant. RESULTS: Our study showed that, when HS patients was compared to controls, the FA was lowest in the anterior, mid-posterior and posterior subregions of the CC. MD and RD were higher in these same segments. No changes were observed in AD. No differences in the CC DTI parameters were detected between right-sided HS and left-sided HS or between concordant and discordant HS patients. Age at initial event, age at epilepsy onset, duration of disease, duration of epilepsy, latency period and seizure frequency were not significantly correlated with the DTI parameters. However, patients who had febrile seizures as initial event exhibited greater intensity and extent of DTI changes. All segments demonstrated volume reduction compared to controls. Significant negative correlation was demonstrated between MD and RD and the volume in the central, midposterior and posterior segments of the CC, and between AD and volume of the posterior segment. We also demonstrated negative correlation between volume and duration of disease and duration of epilepsy. CONCLUSIONS: This study showed diffusion abnormalities in specific areas of the CC and diffuse atrophy in patients with unilateral HS, which may be secondary to seizures propagation along specific pathways leading to secondary changes in brain white matter. The history of febrile seizure is related to greater involvement of the CC

A esquizofrenia é um transtorno mental de alta complexidade e até o presente momento nenhuma teoria conseguiu explicar completamente sua etiologia. Uma dessas teorias acredita que a transferência de informações entre os hemisférios de pacientes com esquizofrenia, que ocorre através do corpo caloso, comissura anterior e posterior, pode estar comprometida. Os objetivos do nosso estudo foram avaliar se existem alterações de conectividade inter-hemisférica (IH) e se essas alterações sofrem influência do gênero, em pacientes portadores de esquizofrenia quando comparados com seus parentes em primeiro grau e controles saudáveis, utilizando-se da imagem de ressonância magnética por tensor de difusão (IRMTD). Participaram do estudo 30 pacientes portadores de esquizofrenia, diagnosticados pelos critérios do Manual diagnóstico e estatístico das doenças mentais em sua quarta edição, os quais foram selecionados entre os pacientes do grupo de medicações atípicas do ambulatório de esquizofrenia e da enfermaria psiquiátrica do Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo; 30 parentes em primeiro grau desses pacientes; e 30 voluntários saudáveis. Todos os sujeitos do estudo foram submetidos a um exame de ressonância magnética, realizado no Centro de Ciências das Imagens e Física Médica de nossa instituição, onde foram adquiridas as sequências volumétricas e difusionais utilizadas em nosso estudo. Em posse das imagens de ressonância magnética dos 90 sujeitos do estudo, realizamos o pós-processamento dessas imagens, utilizando o software BrainVoyager QX® versão 2.4, com o intuito de obtermos, por meio dos dados provenientes da IRMTD, os mapas de anisotropia fracional (AF) e difusibilidade média (DM). Com esses mapas em mãos, procedemos à análise estatística do estudo, denominada de análise de covariância voxel a voxel (VANCOVA), no cérebro todo. Nessa análise, utilizamos a idade como covariável e verificamos a influência do gênero nos resultados encontrados. Nossos resultados 6 evidenciaram que os pacientes portadores de esquizofrenia apresentaram valores de AF e DM alterados em estruturas homólogas ao corpo caloso e áreas frontais adjacentes. Assim, podemos afirmar que descobrimos perda de conectividade IH nesses mesmos pacientes. Por meio de nosso estudo, descobrimos também a influência do gênero nos valores de AF e DM encontrados e então, consequentemente, podemos dizer que a conectividade IH de pacientes portadores de esquizofrenia sofreu influência do sexo. A idade também mostrou influenciar a conectividade IH de nossos pacientes. Com o atual conceito de que alterações de AF e DM podem ser encaradas como indicativos de comprometimento da mielina, e sabendo que a mielina participa diretamente das reações neuroquímicas do sistema glutamatérgico cerebral, também podemos dizer que o sistema glutamatérgico que participa da conectividade IH desses pacientes encontrava-se comprometido. / Schizophrenia is a highly complex mental disorder and no theory to date was able to fully explain the etiology of this disorder. One of the existing theories advocates that interhemispheric communication, which occurs through the corpus callosum and the anterior and posterior commissures, might be impaired in schizophrenia. Our study was designed to investigate whether there are interhemispheric connectivity (IC) alterations in schizophrenia and whether these alterations are influenced by gender through the comparison of schizophrenia patients with their first-degree relatives and healthy controls using diffusion tensor imaging (DTI). We enrolled 30 schizophrenia patients diagnosed according to the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders and selected from the Group of Atypical Medications of the Schizophrenia Outpatient Clinic and the psychiatric ward of the Ribeirão Preto Medical School University Hospital, 30 first-degree relatives of these patients and 30 healthy volunteers. All subjects underwent magnetic resonance imaging (MRI) scans for the acquisition of volumetric and diffusion sequences. The images were post-processed using BrainVoyager QX® version 2.4 to create fractional anisotropy (FA) and mean diffusivity (MD) maps from DTI data. The resulting data were analyzed using voxel-to- voxel analysis of covariance (VANCOVA) for the whole brain. In this analysis, we used age as a co-variable and assessed the influence of gender. Our results showed that schizophrenia patients had altered FA and MD values in structures homologous to the corpus callosum and adjacent frontal areas, suggestive of IC loss in the patients. We also found that gender influenced FA and MD values and, therefore, that IC in schizophrenia patients is influenced by gender. Age was also found to influence IC in our patients. Based on the current conception that FA and MD alterations may indicate myelin impairment and knowing that myelin participates directly in neurochemical reactions of the glutamatergic system in the brain, we can infer that the glutamatergic system, which is implicated in IC, is affected in schizophrenia and is influenced by gender.

L'environnement sous-marin compliqué et la pauvre vision sous-marine font le robot câblé sous-marin super-mini-à peine pour être contrôlés. Traditionnellement, la méthode de contrôle manuelle par les opérateurs est adoptée par cette sorte de robots. Malheureusement, les robots peuvent à peine travailler normalement dans ces circonstances pratiques. Donc, pour surmonter ces manques et améliorer les capacités de ces robots câblés sous-marins, ce papier propose plusieurs améliorations, en incluant le design de système, le design de contrôleur de mouvement, la reconnaissance d'obstacle en trois dimensions et les technologies de reconstruction de sentier en trois dimensions etc. (1) Super-mini sous-marins de conception système de robot: plusieurs programmes d'amélioration et d'idées de conception importants sont étudiés pour la super-mini robot sous-marin (2) La conception du contrôleur de mouvement du robot sous-marin dans des circonstances compliquées est étudiée. Un nouveau réseau de neurones adaptatif coulissantes contrôleur de mode avec le contrôleur paramètre équilibrée est proposé. Basé sur la théorie de la gestion adaptative floue contrôleur de mode coulissant , un algorithme amélioré est également proposé et appliqué à l'robot sous-marin. (3) Recherche de reconstructions d'environnement sous-marines en trois dimensions : les algorithmes et les expériences de reconstructions d'environnement sous-marines sont enquêtés. L'algorithme de traitement d'image de DT-MRI et la théorie de reconstructions d'obstacle en trois dimensions sont adoptés et améliorés pour l'application du robot sous-marin. / The complicated underwater environment and the poor underwater vision make super-mini underwater cable robot hardly to be controlled. Traditionally, the manual control method by operators is adopted by this kind of robots. Unfortunately, the robots can hardly work normally in these practical circumstances. Therefore, to overcome these shortcomings and improve the abilities of these underwater cable robots, this paper proposes several improvements, including the system design, the motion controller design, three dimensional obstacle recognition and three dimensional path reconstruction technologies etc. The details are displayed as follow: (1) Super-mini underwater robot system design: several improvement schemes and important design ideas are investigated for the super-mini underwater robot.(2) Super-mini robot motion controller design: The motion controller design of underwater robot in complicated circumstance is investigated. A new adaptive neural network sliding mode controller with balanced parameter controller (ANNSMB) is proposed. Based on the theory of adaptive fuzzy sliding mode controller (AFSMC), an improved algorithm is also proposed and applied to the underwater robot. (3)Research of three dimensional underwater environment reconstructions: The algorithms and the experiments of underwater environment reconstructions are investigated. DT-MRI image processing algorithm and the theory of three dimensional obstacle reconstructions are adopted and improved for the application of the underwater robot. (4) The super-mini underwater robot path planning algorithms are investigated.

Cette thèse "Tractographie cardiaque optimale utilisant l'IRM du tenseur de diffusion" à pour but de proposer et d'étudier une nouvelle formulation globale de la tractographie cardiaque à partir d'images de tenseur de diffusion synthétisant les données pondérées en diffusion. Les raisons sous-jacentes ayant conduits à une nouvelle formulation sont multiples. Les méthodes existantes sont pour la plupart locales comme les algorithmes de « streamline » (ligne de champ) et sont sujettes à de nombreuses imperfections, en particulier, leur faible robustesse par rapport au bruit dans les données. Un autre problème de ce type d'approches basé sur la résolution d'équations différentielles est leur dépendances quant à l'initialisation, ce dont notre méthode s'est totalement affranchit. L'autre but de cette thèse est de déterminer un ou plusieurs critères numériques pour comparer et qualifier les objets fibres. En effet, même s'il semble facile de caractériser qualitativement les fibres de façon visuelle, la création de mesures pour caractériser les fibres soit dans l'absolue, soit en comparaison aux données ou à d'autres fibre relève d'une toute autre approche. / This thesis "Optimal cardiac tractography using DT-MRI" offers and studies a new formulation of cardiac tractography based on the use of diffusion tensor images that synthetize the information of the diffusion weighted images. The underlying reasons that led to a new formulation are manifold. Existing methods are mostly based on local data, such as the streamlining algorithms, and thus are subject to many imperfections, especially they are not robust to noise in the data. Another problem with this type of approach based on solving differential equations is their dependency on initialization, unlike the method under study. The other aim of this thesis is to determine one or more numerical criteria to compare and qualify fibers. Even though it seems easy to qualitatively characterize fibers based on the visualization, creating measures to characterize the fibers, either in absolute or in comparison to the data or other fibers, is actually challenging.