L'imagerie par résonance magnétique (IRM) est une technique d'imagerie médicale très riche et en plein essor. Elle permet d'obtenir de hautes résolutions temporelle et spatiale, et une très bonne caractérisation tissulaire. Malheureusement, les activités physiologiques de la circulation et de la respiration induisent des mouvements qui interfèrent avec le processus d'acquisition, assez lent, générant des artéfacts. D'un côté, l'exploration par IRM des organes thoraco-abdominaux en est perturbée, mais d'un autre côté c'est un outil non-invasif et précis d'analyse. Ainsi, nous avons montré que la course du diaphragme était de l'ordre de 1 à 2 cm dans une population de patients atteints de mucoviscidose, comme chez les sujets normaux, et légèrement plus importante en postérieur qu'en antérieur. Au cours d'une autre étude, nous avons observé que les déplacements crânio-caudaux du rein étaient aussi importants chez le nourrisson que chez l'adulte, avec des conséquences en imagerie fonctionnelle. Les méthodes gestion de ces mouvements, comme l'apnée ou la synchronisation sur des capteurs externes ou internes, restent cependant imparfaites. Nous montrons comment améliorer la qualité des images pulmonaires chez les patients atteints de mucoviscidose par une technique de double synchronisation cardiaque et respiratoire développée au laboratoire, et comment nous avons pu réaliser des séquences de ciné-cardiaque de haute qualité en respiration libre par utilisation de l'algorithme GRICS. Enfin, nous présentons plusieurs études portant sur l'analyse cinétique des traceurs, illustrant les contraintes particulières à cette situation, et posons les conditions d'un recalage efficient. / Magnetic Resonance Imaging (MRI) has become a major medical Imaging technique thanks to high temporal and spatial resolution, as well as to its abilities to distinguish between tissues. On one hand, MRI examinations of thoracic and abdomino-pelvic organs are compromised by the motions induced by circulation and respiration, but on the other hand, MRI is a non-invasive and precise tool to study these displacements. We have shown, in a group of patients with cystic fibrosis (CF), that the diaphragmatic course was around 1 to 2cm, as it is in normal subjects. In another study, we have found that motions of the kidney was in the same range in infants and in adults, despite the difference in the size of this organ; this is a major cause of error when performing functional analysis. Managing these motions is based upon breath holding and synchronization, both remaining imperfect. Thus, we showed how an in-lab dual synchronization, both cardiac and respiratory, improved quality of lung images in the patients with CF, and how we managed realizing high quality cardiac cine-MRI using the GRICS algorithm. At last, we discuss the specific difficulties of kinetic imaging of contrast agents through a few studies, and explain the bases of an efficient registration method.

Made available in DSpace on 2016-12-06T17:07:07Z (GMT). No. of bitstreams: 1 PRE TEXTUAIS.pdf: 127112 bytes, checksum: 5eefcd8dfe8d7cdbbea6a7cc5e83298a (MD5) Previous issue date: 2004-02-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The aim of this work was to build and to validate an instrument to evaluate the breathing musculature through the difference of the thoracic and abdominal perimeter during the breathing and an evaluation procedure for the same. The study was characterized as experimental research and technological development. The collections were accomplished in the Laboratory of Biomechanics of CEFID/UDESC with 10 healthy individuals, students of CEFID, age between 20 and 30 years. Some of the procedures adopted for the process of validation were the theoretical validity, the experimental validity, the calibration of the sensor and the definition of the procedure to be used in the collections. The prototype was built being used a displacement encoder with digital processing and resolution of 5,9 points/mm. The acquisition of the data was made through the program AmLabII©, that is an acquisition system, processing and storage of signs and data, management events and it works in real time, availabling data in the digital and analogical form. Two collection procedures were accomplished, one in that the measures of PImáx. and PEmáx they were accomplished simultaneously with the measures of thoracic displacement, in spine decubitus, and other in that these measures were done separately, first the pressure measures, in the seated position, and after the displacement, in spine decubitus. To determine the validity and the trustworth of the equipment, being followed the principle of lineal measures; and to the measures of variation of the thoracic and abdominal perimeter obtained for the experimental validity, the descriptive statistics was used ( x , s and CV%). To verify if there was correlation among the measures of variation of the perimeter with the breathing pressures the correlation of Pearson it was applied, with p £ 0,05. The results found in the protocols 1 and 2 indicate that is necessary to reformulate the protocol that will be adopted, in way to optimize the method. In relation to the construction of the prototype, this met the expectations with relationship to the possibility of registering the variation of the width of the thoraco-abdominal movements for the difference of the perimeter. The system presented a high resolution and good linearity of the measures, however, it is needed to accomplish more tests to verify the repeatetibility of the measures and your consistence. With relationship to the procedures adopted in the protocols 1 and 2, it is believed that the instrument and the method are viable, however there is need to verify the number of repetitions adopted is enough and which assists the clinical needs better of the protocols. It was also observed the need of modifying the position adopted for collects of the measures of breathing pressures and of the variation of the thoracoabdominal perimeters, so that are possible more trustworthy comparisons with other methods of breathing evaluation. A correlation significant statiscly wasn´t obtained among the measures of breathing pressures with the variation of the thoraco-abdominal perimeter in the protocol 1, however, being traced the graphs of the pressure by the displacement obtained vii indications of the possibility of obtaining the indulgence. That idea was reinforced starting from the experimental calculation accomplished with a system that simulates the human breathing. However, it is needed more studies to arrive to the ideal number of repetitions and later how to obtain those parameters in humans. / O objetivo deste trabalho foi construir e validar um instrumento para avaliar a musculatura respiratória através da diferença do perímetro torácico e abdominal durante a respiração e um procedimento de avaliação para o mesmo. O estudo caracterizou-se como pesquisa experimental e de desenvolvimento tecnológico. As coletas foram realizadas no Laboratório de Biomecânica do CEFID/UDESC com 10 indivíduos saudáveis, estudantes do CEFID, com idades entre 20 e 30 anos. Alguns dos procedimentos adotados para o processo de validação do instrumento foram a validade teórica, a validade experimental, a calibração do sensor e a definição do procedimento a ser utilizado nas coletas. O protótipo foi construído utilizando-se um encoder de deslocamento linear com processamento digital e resolução de 5,9 pontos/mm. A aquisição dos dados foi feita através do programa AmLabII©, que é um sistema de aquisição, processamento e armazenamento de sinais e dados, gerencia eventos e trabalha em tempo real, disponibilizando dados na forma digital e analógica. Foram realizados dois procedimentos de coleta, um em que as medidas de PImáx. e de PEmáx foram realizadas simultaneamente com as medidas de deslocamento torácico, em decúbito dorsal, e outro em que estas medidas foram feitas separadamente, as medidas de pressão, na posição sentada, e em seguida as de deslocamento, em decúbito dorsal. Para determinar a validade e a fidedignidade do equipamento, seguindo-se o princípio de medidas lineares; e para as medidas de variação do perímetro torácico e abdominal, obtidas para a validade experimental, foi utilizada a estatística descritiva ( x , s e CV%). Para verificar se houve correlação entre as medidas de variação do perímetro com as pressões respiratórias foi aplicada a correlação de Pearson, com p £ 0,05. Os resultados encontrados nos protocolos 1 e 2 indicam que é preciso reformular o protocolo que será adotado, de forma a otimizar o método. Em relação à construção do protótipo, este correspondeu às expectativas quanto à possibilidade de registrar a variação da amplitude dos movimentos tóraco-abdominais pela diferença do perímetro. O sistema apresentou alta resolução e boa linearidade das medidas, contudo, necessita-se realizar mais testes para verificar a repetitibilidade das medidas e sua consistência. Quanto aos procedimentos adotados, acredita-se que o instrumento e o método são viáveis, porém há necessidade de verificar se o número de repetições adotado é suficiente e qual dos protocolos atende melhor as necessidades clínicas. Também se observou a necessidade de modificar a posição adotada para as coleta das medidas de pressões respiratórias e da variação dos perímetros tóraco-abdominais, para que sejam possíveis comparações mais fidedignas com outros métodos de avaliação respiratória. Não se obteve correlação estatisticamente significativa entre as medidas de pressões respiratórias com as de variação do perímetro tóraco-abdominal no protocolo 1, porém, traçando-se os gráficos da pressão pelo deslocamento obtivemos indícios da possibilidade de obter-se a complacência. Essa idéia foi reforçada a partir do cálculo experimental realizado com o sistema de simulação do sistema respiratório humano. Porém, necessita-se de mais estudos para chegar-se ao número ideal de repetições e posteriormente como obter esses parâmetros em humanos.

Les lésions traumatiques de la moelle épinière entraînent de graves conséquences d’un point de vue personnel, physique et social chez les individus qui en sont victimes. La prise en charge médicale et chirurgicale de ces patients évolue au fil de l’amélioration des connaissances sur ce qui favorise la récupération neurologique et la qualité de vie à long terme. Pour le chirurgien du rachis, les facteurs modifiables qui influencent de façon significative l’issue neurologique à long terme chez les blessés médullaires thoraco-lombaires sont peu explorés dans la littérature. Le délai entre le trauma et l’exécution du geste chirurgical est un de ces facteurs, mais la définition de chirurgie précoce chez cette population spécifique demeure à être objectivée. De plus, il n’y a pas de paramètres sur le scan préopératoire ayant été décrit pour aider la prise en charge en fonction de l’issue neurologique à long-terme. L’objectif général de ces travaux est de préciser ce qui influence la récupération neurologique chez les patients paraplégiques ayant subi une fracture dans la région thoraco-lombaire et évaluer l’impact de la morphologie de la fracture sur l’effet du délai entre le traumatisme et la chirurgie de décompression et de stabilisation de la colonne vertébrale. Le premier volet de ce mémoire concerne l’étude du seuil de délai chirurgical associé à une récupération neurologique optimale. Pour ce faire, une étude clinique rétrospective a été menée en évaluant plusieurs issues neurologiques à long terme chez une cohorte prospective de 35 patients blessés médullaires secondairement à un traumatisme vertébral de la région thoraco-lombaire. Déterminer de façon objective le seuil de délai optimal pour la récupération neurologique a été possible en utilisant une méthode statistique faisant intervenir des modèles de prédiction sous la forme d’arbres décisionnels élaborés par partition objective récursive. Cette méthode a démontré que la chirurgie de décompression et de stabilisation entreprise dans les 21 heures suivant le moment du traumatisme augmente la probabilité d’améliorer l’état neurologique 12 mois après le traumatisme, en termes de sévérité (grade) de la lésion et du niveau neurologique. Le deuxième volet du mémoire concerne l’étude de la morphologie de la fracture la plus commune de la région thoraco-lombaire, la fracture de type « burst ». De nombreux paramètres radiologiques sont connus et définissent ce type de fracture mais aucun n’a été bien évalué en fonction de la récupération neurologique à long terme. Une deuxième étude clinique rétrospective implique l’étude du scan préopératoire à la recherche de paramètres reliés à l’issue neurologique chez les blessés médullaires avec atteinte motrice sévère. Trois caractéristiques morphologiques fortement associées à la récupération ont été identifiées : la présence d’une fracture complète de la lame, le recul de plus de 4 mm de la portion inférieure du mur postérieur du corps vertébral et la présence de comminution du fragment de corps vertébral rétropulsé dans le canal spinal. Ces paramètres sont des facteurs de pronostic défavorable de récupération neurologique plus importants que l’atteinte neurologique initiale ou l’estimation du degré d’énergie impliquée durant le traumatisme. Puisque ces paramètres décrivent la géométrie du canal spinal endommagé lors d’une fracture de type « burst », ils offrent un reflet de l’énergie locale dissipée dans le canal spinal et transmise aux éléments neuraux. Le troisième volet du mémoire implique l’intégration des nouvelles connaissances issues des deux articles présentés, à la recherche de l’influence de certains paramètres morphologiques sur l’effet de la chirurgie précoce sur la récupération neurologique. Les analyses complémentaires effectuées sur la cohorte de patients atteints de fracture de type « burst » n’ont pas démontré que l’avantage procuré par une chirurgie de décompression et stabilisation précoce était modifié ou altéré par la présence d’un des paramètres démontrés comme importants d’un point de vue neurologique. Ces travaux permettent de mieux guider le chirurgien du rachis dans la planification du geste chirurgical de par une meilleure compréhension des facteurs prédictifs de l’issue neurologique à long terme. En déterminant un seuil de délai objectif optimal de 21 heures, ils permettent d’établir une recommandation pour la définition même de la chirurgie précoce chez le blessé médullaire thoraco-lombaire. Ils proposent également une base pour l’étude subséquente de nouveaux paramètres clés quantifiables sur le scan préopératoire, un examen essentiel et disponible chez tous les patients, et de leur relation potentielle avec le choix de l’approche chirurgicale idéale ainsi qu’avec de multiples issues neurologiques et non-neurologiques. / Traumatic spinal cord injury (TSCI) is a debilitating condition that leads to many adverse consequences on a personal, physical and social standpoint for the injured victim. Medical and surgical care evolved along with the progression of understanding regarding what factors lead to better neurological recovery and overall quality of life in paralyzed patients. With respect to surgical care, modifiable factors significantly related to neurological recovery in thoracolumbar TSCI are not well known. In this regard, the optimal timing threshold for surgical spinal decompression and stabilization has not been demonstrated objectively. Moreover, there are no radiological parameter on the pre-operative computed tomography scan (CT scan) that have been shown to predict long term neurological outcome. The main goal of the presented work is to provide precise identification of such factors, and therefore evaluate the impact of the spine fracture specific morphological features on the effect of early surgical care. The first part involves the assessment of the optimal surgical timing threshold for neurological recovery. A retrospective clinical study was conducted to evaluate several neurological outcome measures in a prospective cohort of 35 thoracolumbar TSCI patients. Thresholds were obtained from the elaboration of prediction models with the use of Classification And Regression Tree (CART) statistical analysis. The first article demonstrated that for optimal recovery of the neurological level of injury, a timing threshold of a maximum of 21 hours should ideally be respected between the traumatic event and the beginning of the surgical intervention. The second part encompasses the study of the morphology of the fractured vertebrae in thoracolumbar burst fractures. Many radiological descriptors are used to describe these severe spine compression injuries but few have been evaluated with regards to neurological recovery. A second retrospective clinical study was conducted and associated a thorough examination of the preoperative CT scan reconstructions to the assessment of long term neurological outcome. Three morphologic parameters were found to be linked to poor prognostic of neurological recovery: complete lamina fracture, comminution of the posteriorly retropulsed fragment and vertebral body postero-inferior corner translation of 4 mm or more. Such features, all three describing the disrupted anatomy of the spinal canal, could be potential indicators of the amount of energy locally dissipated to the neural elements. These parameters were found to be more important to predict neurological outcome than the initial neurologic examination and global trauma energy indicators. The third part integrates the notions derived from the two presented studies and aims to assess for the influence of the presence of specific fracture parameters on the effect of early surgery regarding neurological outcome. Additional analyses did not show that the advantage of early surgery, defined in the first article, was influenced by the presence of any of the relevant fracture features demonstrated in the second article. Therefore, this work emphasizes on the importance of early surgery for better neurological recovery and serves to guide the surgeon in planning the timing of the intervention. Defining the concept of early surgery is key in implementing future retrospective or prospective research protocols. It also highlights the importance of new morphological features of the most common type of thoracolumbar fracture. It sets standards for further research involving preoperative CT scan parameters and their potential relationship with surgical approach, neurological and non-neurological outcomes.