O objetivo do presente estudo foi avaliar a efusão e o posicionamento do disco articular através de imagens por ressonância magnética nuclear (RMN) pré e pós-operatórios de duas técnicas de artrocentese da articulação temporomandibular. Foram incluídos 26 pacientes com deslocamento de o disco articular sem redução (DDSR), divididos aleatoriamente em dois grupos: artrocentese com 1 agulha com distensão do compartimento superior da ATM (A1) e artrocentese convencional com 2 agulhas (A2). Para comparação dos valores da efusão articular entre as intervenções nos diferentes momentos (antes e após um ano das artrocenteses), foi utilizado o teste qui-quadrado. Todas as análises foram realizadas com nível de significância de 5%. Em relação à efusão, após a realização dos tratamentos, foi observada uma diferença estatisticamente significativa entre as diferentes categorias de efusão (p=0,009), sendo essa diferença evidente no grupo de artrocentese convencional. Do total da amostra, apenas um caso não houve qualquer modificação do posicionamento do disco articular. Pode-se concluir que a artrocentese convencional foi capaz de alterar a variável efusão de maneira estatisticamente significativa, enquanto a artrocentese de agulha única e distensão do compartimento superior não. Ambas as técnicas foram responsáveis por alterar o posicionamento da cabeça mandibular, ou do complexo cabeça-disco, projetando-os nessa última situação para uma posição mais anterior o que pode ser verificado no exame de RMN final, com um aumento da distância interincisal máxima. O uso de artrocentese com emprego de uma única agulha é uma técnica mais simples, do que a artrocentese convencional o que possibilita um maior conforto para o paciente com menor tempo de procedimento e com resultados satisfatórios. / The aim of the present study was to evaluate the effusion and positioning of the articular disc through nuclear magnetic resonance imaging (NMRI) before and after two different arthrocentesis techniques for the temporomandibular joint. 26 patients with dislocation of the articular disc without reduction (ADDwoR) were included, and randomly divided into two groups: arthrocentesis using 1 needle with distention of the upper compartment of the TMJ (A1), and conventional arthrocentesis with 2 needles (A2). The chi-square test was used to compare the joint effusion values between the interventions at different moments (before and after one year of arthrocentesis). All analyzes were performed with a significance level of 5%. Regarding effusion, after the treatments, a statistically significant difference was observed between the different effusion categories (p = 0.009), which was evident in the conventional arthrocentesis group. Of the total sample, only one case did not have a modification of the position of the articular disc. It can be concluded that conventional arthrocentesis was able to change the effusion variable in a statistically significant way, whereas the single needle arthrocentesis and distention of the upper compartment did not. Both techniques were responsible for altering the position of the mandibular head, or the disc-head complex, projecting them in the latter situation, to a more anterior position with an increase in the maximum interincisal distance verified in the final NMRI examination. Arthrocentesis with a single needle is simpler than the conventional technique, for it allows greater comfort to the patient, a shorter procedure and satisfactory results.

Thesis (Ph. D.)--Carleton University, 2004. / Includes bibliographical references (p. 107-116). Also available in electronic format on the Internet.

O objetivo do presente estudo foi avaliar a efusão e o posicionamento do disco articular através de imagens por ressonância magnética nuclear (RMN) pré e pós-operatórios de duas técnicas de artrocentese da articulação temporomandibular. Foram incluídos 26 pacientes com deslocamento de o disco articular sem redução (DDSR), divididos aleatoriamente em dois grupos: artrocentese com 1 agulha com distensão do compartimento superior da ATM (A1) e artrocentese convencional com 2 agulhas (A2). Para comparação dos valores da efusão articular entre as intervenções nos diferentes momentos (antes e após um ano das artrocenteses), foi utilizado o teste qui-quadrado. Todas as análises foram realizadas com nível de significância de 5%. Em relação à efusão, após a realização dos tratamentos, foi observada uma diferença estatisticamente significativa entre as diferentes categorias de efusão (p=0,009), sendo essa diferença evidente no grupo de artrocentese convencional. Do total da amostra, apenas um caso não houve qualquer modificação do posicionamento do disco articular. Pode-se concluir que a artrocentese convencional foi capaz de alterar a variável efusão de maneira estatisticamente significativa, enquanto a artrocentese de agulha única e distensão do compartimento superior não. Ambas as técnicas foram responsáveis por alterar o posicionamento da cabeça mandibular, ou do complexo cabeça-disco, projetando-os nessa última situação para uma posição mais anterior o que pode ser verificado no exame de RMN final, com um aumento da distância interincisal máxima. O uso de artrocentese com emprego de uma única agulha é uma técnica mais simples, do que a artrocentese convencional o que possibilita um maior conforto para o paciente com menor tempo de procedimento e com resultados satisfatórios. / The aim of the present study was to evaluate the effusion and positioning of the articular disc through nuclear magnetic resonance imaging (NMRI) before and after two different arthrocentesis techniques for the temporomandibular joint. 26 patients with dislocation of the articular disc without reduction (ADDwoR) were included, and randomly divided into two groups: arthrocentesis using 1 needle with distention of the upper compartment of the TMJ (A1), and conventional arthrocentesis with 2 needles (A2). The chi-square test was used to compare the joint effusion values between the interventions at different moments (before and after one year of arthrocentesis). All analyzes were performed with a significance level of 5%. Regarding effusion, after the treatments, a statistically significant difference was observed between the different effusion categories (p = 0.009), which was evident in the conventional arthrocentesis group. Of the total sample, only one case did not have a modification of the position of the articular disc. It can be concluded that conventional arthrocentesis was able to change the effusion variable in a statistically significant way, whereas the single needle arthrocentesis and distention of the upper compartment did not. Both techniques were responsible for altering the position of the mandibular head, or the disc-head complex, projecting them in the latter situation, to a more anterior position with an increase in the maximum interincisal distance verified in the final NMRI examination. Arthrocentesis with a single needle is simpler than the conventional technique, for it allows greater comfort to the patient, a shorter procedure and satisfactory results.

O objetivo do presente estudo foi avaliar a efusão e o posicionamento do disco articular através de imagens por ressonância magnética nuclear (RMN) pré e pós-operatórios de duas técnicas de artrocentese da articulação temporomandibular. Foram incluídos 26 pacientes com deslocamento de o disco articular sem redução (DDSR), divididos aleatoriamente em dois grupos: artrocentese com 1 agulha com distensão do compartimento superior da ATM (A1) e artrocentese convencional com 2 agulhas (A2). Para comparação dos valores da efusão articular entre as intervenções nos diferentes momentos (antes e após um ano das artrocenteses), foi utilizado o teste qui-quadrado. Todas as análises foram realizadas com nível de significância de 5%. Em relação à efusão, após a realização dos tratamentos, foi observada uma diferença estatisticamente significativa entre as diferentes categorias de efusão (p=0,009), sendo essa diferença evidente no grupo de artrocentese convencional. Do total da amostra, apenas um caso não houve qualquer modificação do posicionamento do disco articular. Pode-se concluir que a artrocentese convencional foi capaz de alterar a variável efusão de maneira estatisticamente significativa, enquanto a artrocentese de agulha única e distensão do compartimento superior não. Ambas as técnicas foram responsáveis por alterar o posicionamento da cabeça mandibular, ou do complexo cabeça-disco, projetando-os nessa última situação para uma posição mais anterior o que pode ser verificado no exame de RMN final, com um aumento da distância interincisal máxima. O uso de artrocentese com emprego de uma única agulha é uma técnica mais simples, do que a artrocentese convencional o que possibilita um maior conforto para o paciente com menor tempo de procedimento e com resultados satisfatórios. / The aim of the present study was to evaluate the effusion and positioning of the articular disc through nuclear magnetic resonance imaging (NMRI) before and after two different arthrocentesis techniques for the temporomandibular joint. 26 patients with dislocation of the articular disc without reduction (ADDwoR) were included, and randomly divided into two groups: arthrocentesis using 1 needle with distention of the upper compartment of the TMJ (A1), and conventional arthrocentesis with 2 needles (A2). The chi-square test was used to compare the joint effusion values between the interventions at different moments (before and after one year of arthrocentesis). All analyzes were performed with a significance level of 5%. Regarding effusion, after the treatments, a statistically significant difference was observed between the different effusion categories (p = 0.009), which was evident in the conventional arthrocentesis group. Of the total sample, only one case did not have a modification of the position of the articular disc. It can be concluded that conventional arthrocentesis was able to change the effusion variable in a statistically significant way, whereas the single needle arthrocentesis and distention of the upper compartment did not. Both techniques were responsible for altering the position of the mandibular head, or the disc-head complex, projecting them in the latter situation, to a more anterior position with an increase in the maximum interincisal distance verified in the final NMRI examination. Arthrocentesis with a single needle is simpler than the conventional technique, for it allows greater comfort to the patient, a shorter procedure and satisfactory results.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. "January 1983"--Cover of photocopy. Two p. of original are reproduced on 1 p. of photocopy. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 151-152).

Current quantitative nuclear magnetic resonance (NMR) technics offer biomarkers that allow performing non-invasive longitudinal studies for the follow up of therapeutic trials in neuromuscular disorders (NMD). In contrast to fat degeneration, the mechanisms of inflammation/oedema/necrosis and fibrosis are characteristic signs of disease activity, which makes their quantification a promising source of crucial biomarkers for longitudinal studies. This thesis work consisted on the implementation of more precise quantitative NMR methods adapted to the clinical study of skeletal muscle (SKM) for : (i) detection and quantification of sites of disease activity by T2-mapping of muscle water ; (ii) investigation of the different pathophysiological mechanisms underlying T2 alterations ; and (iii) Detection and quantification of muscle fibrosis. We implemented two methods for T2 mapping of muscle water. The first one is based on a multi-spin-echo sequence du type CPMG. In this method the 1H-NMR signals from water and lipids are acquired simultaneously. The acquired data are fitted to a tri-exponential model, in which water and fat signals are separated by exploring the T2 difference between water and fat. This method allows extraction of muscle water T2-value in the presence of fat infiltration. The second method is based on a " partially spoiled steady state free precession " (pSSFP) sequence. In contrast to the first method, which demands a sophisticated post-treatment of images acquired at 17 different echo-times, with the pSSFP a T2-mapping is extracted from two 3D data sets. 3D acquisition is compatible with spectrally selective water excitation, which eliminates signal contribution from lipids. Both methods were validated experimentally on patients and healthy subjects. The results demonstrated their capacity to detect and quantify disease activity sites. This 2 works have been published in two international journals : Azzabou, de Sousa, Araujo, & Carlier, 2014. Journal of Magnetic Resonance Imaging. DOI 10.1002/jmri.24613 (in press); et de Sousa, Vignaud, Araujo, & Carlier . 2012. Magnetic Resonance in Medicine. 67:1379-1390. Although it was shown to reveal disease activity, mono-exponential T2 of muscle water is non-specific to what concerns the mechanisms underlying its alterations. It has been long known that T2 relaxation in SKM tissue is multi-exponential. This is currently accepted to reveal anatomical compartmentation of myowater. We implemented a method for localized spectroscopic CPMG acquisition. CPMG data respect echo-time sampling and signal to noise ration limits for allowing robust multiexponential analysis. This work allowed us to establish a compartmentation model that perfectly explains the multi-exponential T2 relaxation observed in SKM tissue. This work was published in the " Biophysical Journal " (Araujo, Fromes & Carlier 2014. New Insights on skeletal muscle tissue compartments revealed by T2 NMR relaxometry. (In press)). Pilot studies performed in patients show promising results and suggest potential application of the method in clinical studies. Fibrosis starts with an excessive accumulation of intramuscular connective tissue (IMCT). We have explored the " Ultrashort time to echo " (UTE) method with the aim to detect and characterize the signal from IMCT. In a first study we characterized in vivo a short T2 component (~500 µs) in SKM, and we collected evidences suggesting that this component might reflect IMCT. Then we implemented a methodology that allowed imaging this short component in SKM tissue for the first time.

A radioterapia de intensidade modulada (IMRT) é uma das mais modernas técnicas radioterapêuticas que permite a entrega de elevadas e complexas distribuição de doses ao volume tumoral, que necessita de novos métodos para o controle de qualidade dos procedimentos efetuados. Nos serviços de radioterapia costuma-se usar para o controle de qualidade do sistema de planejamento, a câmara de ionização para verificação pontual da dose e um dispositivo com diodos semicondutores (MapCHECK2) para a verificação bidimensional em um plano da fluência planejada, entretanto, para a verificação tridimensional dessas distribuições de doses ainda não há um dosímetro consolidado na rotina clínica. Nesse contexto, para a dosimetria tridimensional se destacam os géis poliméricos. Neste trabalho foram feitas a dosimetria convencional, pontual e bidimensional como se faz na rotina clínica e a dosimetria tridimensional utilizando o gel polimérico Magic-f, que apresenta a distribuição de dose volumétrica. Para este trabalho foi escolhido o tratamento de câncer de próstata, pois na atualidade é um dos tipos de cânceres mais comuns entre os homens. No contexto da dosimetria gel, para se obter a informação volumétrica é necessária uma técnica de imagem, no presente caso foram utilizadas imagens por ressonância magnética (magnetic resonance imaging, MRI). A partir dessas imagens é possível determinar as distribuições de doses processando-as em um software desenvolvido pelo grupo que determina as taxas de relaxação R2 associada à dose absorvida e posteriormente comparar as imagens obtidas com as imagens do sistema de planejamento. Para isso, se obteve dez cortes ao longo de cada simulador físico ou fantom em que sua comparação foi feita com a respectiva fatia do sistema de planejamento, na posição correspondente. Para uma avaliação quantitativa foi utilizado o conceito de índice gama, no critério padrão da radioterapia, 3% da dose e 3mm de distância de concordância. Os resultados obtidos com a dosimetria gel se mostram de acordo com os controles de qualidade convencionais e oferecem uma visão global da distribuição de dose no volume alvo. / The intensity modulated radiotherapy (IMRT) is one of the most modern radiotherapeutic technique that enables the delivery of high and complexes conformational doses to the tumor volume, that requires new methods for the quality assurance of the procedures performed. Radiotherapy services usually perform quality assurance of the planning system with the ionization chamber for spot-checking and an array of semiconductor diodes (MapCHECK2) to check on a two-dimensional plane, however for tridimensional dose verification does not exist an established dosimeter in the clinical routine. In this context, for three-dimensional dosimetry the polymeric gels were used. In This work the conventional one and two-dimensional dosimetry as employed in the clinical routine, and the three-dimensional dosimetry using polymer gel MAGIC- f, which provide the volumetric dose distribution. Prostate cancer clinical cases were chosen for this work because this kind of tumor is one of the most common cases in male individuals. In the context of dosimetry gel to obtain volumetric information an imaging technique is necessary, in this case the magnetic resonance imaging (MRI), was used to measure the dose. From these images it is possible to determine the distributions of doses processing them in a software developed by our research group that determines R2 relaxation rates associated with the absorbed dose and subsequently compare the images obtained with the images of the planning system. For this, ten slices were obtained along each phantom, and comparisons were made with the respective slice of the treatment planning system, in the corresponding position. For a quantitative evaluation of the gamma index , in the standard criterion in radiotherapy, 3 % dose and 3 mm distance to agreement was used. The results obtained shown that gel dosimetry agrees with the conventional quality controls and provide an overview of dose distribution in the target volume.

A radioterapia de intensidade modulada (IMRT) é uma das mais modernas técnicas radioterapêuticas que permite a entrega de elevadas e complexas distribuição de doses ao volume tumoral, que necessita de novos métodos para o controle de qualidade dos procedimentos efetuados. Nos serviços de radioterapia costuma-se usar para o controle de qualidade do sistema de planejamento, a câmara de ionização para verificação pontual da dose e um dispositivo com diodos semicondutores (MapCHECK2) para a verificação bidimensional em um plano da fluência planejada, entretanto, para a verificação tridimensional dessas distribuições de doses ainda não há um dosímetro consolidado na rotina clínica. Nesse contexto, para a dosimetria tridimensional se destacam os géis poliméricos. Neste trabalho foram feitas a dosimetria convencional, pontual e bidimensional como se faz na rotina clínica e a dosimetria tridimensional utilizando o gel polimérico Magic-f, que apresenta a distribuição de dose volumétrica. Para este trabalho foi escolhido o tratamento de câncer de próstata, pois na atualidade é um dos tipos de cânceres mais comuns entre os homens. No contexto da dosimetria gel, para se obter a informação volumétrica é necessária uma técnica de imagem, no presente caso foram utilizadas imagens por ressonância magnética (magnetic resonance imaging, MRI). A partir dessas imagens é possível determinar as distribuições de doses processando-as em um software desenvolvido pelo grupo que determina as taxas de relaxação R2 associada à dose absorvida e posteriormente comparar as imagens obtidas com as imagens do sistema de planejamento. Para isso, se obteve dez cortes ao longo de cada simulador físico ou fantom em que sua comparação foi feita com a respectiva fatia do sistema de planejamento, na posição correspondente. Para uma avaliação quantitativa foi utilizado o conceito de índice gama, no critério padrão da radioterapia, 3% da dose e 3mm de distância de concordância. Os resultados obtidos com a dosimetria gel se mostram de acordo com os controles de qualidade convencionais e oferecem uma visão global da distribuição de dose no volume alvo. / The intensity modulated radiotherapy (IMRT) is one of the most modern radiotherapeutic technique that enables the delivery of high and complexes conformational doses to the tumor volume, that requires new methods for the quality assurance of the procedures performed. Radiotherapy services usually perform quality assurance of the planning system with the ionization chamber for spot-checking and an array of semiconductor diodes (MapCHECK2) to check on a two-dimensional plane, however for tridimensional dose verification does not exist an established dosimeter in the clinical routine. In this context, for three-dimensional dosimetry the polymeric gels were used. In This work the conventional one and two-dimensional dosimetry as employed in the clinical routine, and the three-dimensional dosimetry using polymer gel MAGIC- f, which provide the volumetric dose distribution. Prostate cancer clinical cases were chosen for this work because this kind of tumor is one of the most common cases in male individuals. In the context of dosimetry gel to obtain volumetric information an imaging technique is necessary, in this case the magnetic resonance imaging (MRI), was used to measure the dose. From these images it is possible to determine the distributions of doses processing them in a software developed by our research group that determines R2 relaxation rates associated with the absorbed dose and subsequently compare the images obtained with the images of the planning system. For this, ten slices were obtained along each phantom, and comparisons were made with the respective slice of the treatment planning system, in the corresponding position. For a quantitative evaluation of the gamma index , in the standard criterion in radiotherapy, 3 % dose and 3 mm distance to agreement was used. The results obtained shown that gel dosimetry agrees with the conventional quality controls and provide an overview of dose distribution in the target volume.

Cette thèse est une contribution à la fois expérimentale, théorique et numérique à l'étude des écoulements bidimensionnels de fluides complexes dans une conduite cylindrique présentant des singularités et dans une géométrie annulaire à cylindres excentrés. Le fluide utilisé est une solution de xanthane à différentes concentrations présentant un caractère non newtonien rhéofluidifiant. L'objectif principal de cette thèse est la caractérisation de l'influence des propriétés rhéofluidifiantes sur le comportement des zones de recirculation, en terme de morphologie, de positionnement et d'intensité, par l'utilisation et le développement de techniques de mesures non intrusives et performantes. La première méthode expérimentale utilisée une technique laser classique: la vélocimétrie par images de particules. La seconde technique mise en oeuvre est une méthode originale: la vélocimétrie par imagerie par résonance magnétique. Elle est utilisée pour la première fois au laboratoire pour la mesure de champ de vitesse d'écoulement de fluides complexes en conduite cylindrique, représentant l'intérêt majeur de cette thèse. La première partie de notre travail consiste en une description rhéologique complète de nos fluides modèles avec la détermination de leur loi de comportement et la mise en évidence de leurs propriétés viscoélastiques, par ailleurs négligeables. Par la suite les mesures de champ de vitesse des écoulements bidimensionnels étudiés et la représentation des lignes de courant montrent que les propriétés rhéofluidifiantes influencent très fortement la structure et la morphologie de ces écoulements et le comportement des zones de recirculation. Par une étude fine nous observons qu'il existe une compétition entre les effets d'inertie et les effets rhéofluidifiants induisant un champ de contrainte variable qui modifie le positionnement et la taille de la zone de recirculation. Nous montrons également que l'augmentation du caractère rhéofluidifiant affaiblit son intensité de la zone de recirculation. Enfin, des simulations numériques utilisant la loi de comportement macroscopique déterminée par rhéométrie classique ont été réalisées avec le logiciel Fluent. Une bonne concordance est observée entre les résultats de ces simulations numériques et les expérimentaux. Cette comparaison permet ainsi de valider le code de calcul et la loi de comportement, utilisée pour les simulations numériques au travers de sa modélisation suivant la loi de Cross, pour les écoulements considérés / This thesis is an experimental and numerical study of structured fluids bidimensional flows in a cylindrical pipe with singularity and in an annular geometry with eccentric cylinders. The objective of this thesis is to characterize the influence of the shear thinning properties on the recirculation zones by using efficient and non-intrusive techniques: particle image velocimetry and velocimetry by nuclear magnetic resonance imaging. Materials are xanthane solutions at different concentrations. In the first part, we determine the rheological and viscoelastic properties of the fluids used. The second part concerns the measured velocity field. It is shown that the shear thinning behavior have a strongly influence on the structure and the morphology of these flows and the pattern of the recirculation zones. Simultaneously, numerical simulations performed by Fluent and using the rheological behavior. A good concordance is observed between the experimental and numerical results. For the flows considered here, this comparison allows to validate the computational code and the behavior law used in the numerical simulations and modelling by a Cross model

Actuellement, des méthodes quantitatives de résonance magnétique nucléaire (RMN) offrent des biomarqueurs qui permettent la réalisation d’études longitudinales pour le suivi de l’évolution des maladies neuromusculaires et des essais thérapeutiques de manière non-invasive. A la différence de la dégénérescence graisseuse, les processus d’inflammation/œdème/nécrose et fibrose sont des signes d’activité des maladies et leurs quantifications constitueraient ainsi de biomarqueurs parfaitement adaptés pour le suivi thérapeutique. Ce travail de thèse a consisté à mettre en place des méthodologies quantitatives plus précises et adaptées à l’étude clinique du muscle pour : (i) détecter et quantifier des sites d’activité de maladies par la cartographie T2 de l’eau ; (ii) identifier les différents processus pathophysiologiques qui sont à l’origine des altérations du T2 ; et (iii) détecter et quantifier la fibrose musculaire. Nous avons implémenté deux méthodes pour la quantification du T2 de l’eau dans le muscle. La première est basée sur une séquence d’écho de spin du type CPMG, où les signaux provenant des protons des lipides et de l’eau sont acquis simultanément et séparés à postériori par un traitement tri-exponentiel qui exploite la différence entre les T2 qui caractérisent les signaux de l’eau et de la graisse. La deuxième technique est basée sur une séquence de « partially spoiled steady state free precession (pSSFP) ». Différemment de la première technique qui nécessite un traitement assez élaboré sur des images acquises à 17 temps d’écho différents, dans la pSSFP la cartographie T2 est extraite à partir de deux séries de données 3D. L’acquisition 3D est compatible avec des techniques de sélection spectrale de l’eau, ce qui évite la contamination par les signaux des lipides. Les deux méthodes ont été validées expérimentalement chez des malades et des sujets sains et ont démontré leur capacité à détecter et quantifier des sites d’activité de maladies. Ces deux travaux font l’objet de deux publications dans des journaux scientifiques internationaux : Azzabou, de Sousa, Araujo, & Carlier, 2014. Journal of Magnetic Resonance Imaging. DOI 10.1002/jmri.24613 (in press); et de Sousa, Vignaud, Araujo, & Carlier . 2012. Magnetic Resonance in Medicine. 67:1379-1390. Malgré le fait de permettre la détection des sites d’activité de maladies, la mesure mono-exponentielle du T2 de l’eau par imagerie reste non-spécifique vis-à-vis des processus physiologiques à l’origine de l’augmentation du T2. Il est connu que la relaxation T2 du muscle squelettique n’est pas mono-exponentielle. Cela est interprété comme une conséquence de la compartimentation anatomique de l’eau tissulaire. Nous avons mis au point une méthode pour l’acquisition localisée de données CPMG. Cette technique permet l’acquisition des données dans des conditions nécessaires pour la réalisation de traitements multi-exponentiels précis. Ce travail nous a permis d’établir un modèle de compartimentation qui explique parfaitement la relaxation T2 dans le muscle. Il a fait l’objet d’un article publié dans le « Biophysical Journal » (Araujo, Fromes & Carlier 2014. New Insights on skeletal muscle tissue compartments revealed by T2 NMR relaxometry. (In press)). Les essais réalisés chez des sujets malades suggèrent un grand potentiel pour l’application de la méthode dans des études cliniques. La formation de la fibrose commence avec une accumulation excessive de tissu conjonctif intramusculaire (TCIM). Nous avons exploité la technique « Ultrashort Time-to-Echo » (UTE) pour essayer de détecter et caractériser le signal du TCIM. Dans une première étude, nous avons caractérisé in vivo une composante à T2 court (~500 µs) dans le muscle, et nous avons trouvé des indices qui suggèrent qu’elle représente le TCIM. Dans une deuxième étude, nous avons mis au point une méthodologie qui a permis d’imager cette composante à T2 court dans le muscle pour la première fois. / Current quantitative nuclear magnetic resonance (NMR) technics offer biomarkers that allow performing non-invasive longitudinal studies for the follow up of therapeutic trials in neuromuscular disorders (NMD). In contrast to fat degeneration, the mechanisms of inflammation/oedema/necrosis and fibrosis are characteristic signs of disease activity, which makes their quantification a promising source of crucial biomarkers for longitudinal studies. This thesis work consisted on the implementation of more precise quantitative NMR methods adapted to the clinical study of skeletal muscle (SKM) for : (i) detection and quantification of sites of disease activity by T2-mapping of muscle water ; (ii) investigation of the different pathophysiological mechanisms underlying T2 alterations ; and (iii) Detection and quantification of muscle fibrosis. We implemented two methods for T2 mapping of muscle water. The first one is based on a multi-spin-echo sequence du type CPMG. In this method the 1H-NMR signals from water and lipids are acquired simultaneously. The acquired data are fitted to a tri-exponential model, in which water and fat signals are separated by exploring the T2 difference between water and fat. This method allows extraction of muscle water T2-value in the presence of fat infiltration. The second method is based on a « partially spoiled steady state free precession » (pSSFP) sequence. In contrast to the first method, which demands a sophisticated post-treatment of images acquired at 17 different echo-times, with the pSSFP a T2-mapping is extracted from two 3D data sets. 3D acquisition is compatible with spectrally selective water excitation, which eliminates signal contribution from lipids. Both methods were validated experimentally on patients and healthy subjects. The results demonstrated their capacity to detect and quantify disease activity sites. This 2 works have been published in two international journals : Azzabou, de Sousa, Araujo, & Carlier, 2014. Journal of Magnetic Resonance Imaging. DOI 10.1002/jmri.24613 (in press); et de Sousa, Vignaud, Araujo, & Carlier . 2012. Magnetic Resonance in Medicine. 67:1379-1390. Although it was shown to reveal disease activity, mono-exponential T2 of muscle water is non-specific to what concerns the mechanisms underlying its alterations. It has been long known that T2 relaxation in SKM tissue is multi-exponential. This is currently accepted to reveal anatomical compartmentation of myowater. We implemented a method for localized spectroscopic CPMG acquisition. CPMG data respect echo-time sampling and signal to noise ration limits for allowing robust multiexponential analysis. This work allowed us to establish a compartmentation model that perfectly explains the multi-exponential T2 relaxation observed in SKM tissue. This work was published in the « Biophysical Journal » (Araujo, Fromes & Carlier 2014. New Insights on skeletal muscle tissue compartments revealed by T2 NMR relaxometry. (In press)). Pilot studies performed in patients show promising results and suggest potential application of the method in clinical studies. Fibrosis starts with an excessive accumulation of intramuscular connective tissue (IMCT). We have explored the « Ultrashort time to echo » (UTE) method with the aim to detect and characterize the signal from IMCT. In a first study we characterized in vivo a short T2 component (~500 µs) in SKM, and we collected evidences suggesting that this component might reflect IMCT. Then we implemented a methodology that allowed imaging this short component in SKM tissue for the first time.