Diffusion Tensor Imaging (DTI) can quantify tissue integrity in normal-appearing white matter (NAWM). NAWM abnormalities present at the earliest time point implicate neurodegeneration operative from the outset of multiple sclerosis (MS). DTI scans were obtained at first attacks from 6 children later diagnosed with MS and 6 children with monophasic demyelination, and from 6 controls, matched for age. DTI scans were also obtained from 22 children with established MS with clinical onset before age 12 years and compared to age-matched controls. Atlas- and tractography-based image processing methods were utilized. DTI metrics distinguished MS patients from patients with monophasic demyelination and from controls at the first attack. Differences in NAWM between children with established early-onset MS and controls were only notable when DTI was obtained in adolescence. DTI provides valuable insights into NAWM in children with MS, although in the youngest patients such changes may require time to develop.

Paediatric posterior fossa tumors are often effectively controlled with a combination of radiation, chemotherapy and surgery. However, therapeutic craniospinal radiation has been associated with widespread cognitive late effects. Working memory is one such cognitive ability that has yet to be fully examined in this clinical population. Bilateral tracts connecting the cerebellum with the DLPFC were delineated using DTI tractography in all participants, replicating the cerebrocerebellar pathway outlined in an animal model. There were observable differences in white matter integrity (quantified by DTI measures of anisotropy, and mean, axial, and radial diffusivity) of the cerebellum-DLPFC pathway in patients versus controls. Additionally, working memory deficits that were found in patients were correlated with DTI indices pertaining to the cerebellum-DLPFC pathway. Therefore, this thesis is the first to explore the possible relations between white matter integrity of this pathway following treatment for paediatric posterior fossa tumors and working memory function.

L'objectif de cette thèse est de développer des méthodes IRM permettant d'étudier l'impact d'une ischémie focale transitoire sur le cerveau de rat nouveau-né. Les techniques utilisées sont l'imagerie à contraste renforcé par le manganèse (MEMRI), l'imagerie du tenseur de diffusion (DTI) ainsi que de façon préliminaire l'imagerie Q-ball (QBI). Le MEMRI après injection intra cérébrale a été utilisé afin d'étudier de manière dynamique le tractus cortico-thalamique, en parallèle le DTI a servi de marqueur de la structuration cérébrale. Les résultats ont montré une atteinte du tractus cortico-thalamique ipsi-latéral, sept et quatorze jours après ischémie. De manière générale le DTI a montré une structuration ralentie à la suite de l'ischémie. A partir de ces résultats la faisabilité d'une méthode d'acquisition rapide et de traitement de données Q-ball a été établie puis testée sur un animal immature. Les méthodes mises en place se sont révélées efficaces dans le suivi de la maturation cérébrale dans des conditions normales ainsi que pathologiques, ouvrant des perspectives d'études liées au développement cérébral.

Background: Gliomas are neuroepithelial tumours classified by cell type and grade. In adults, low-grade gliomas are comprised mainly of astrocytomas and oligodendrogliomas grade II. The aim was to non-invasively characterise suspected low-grade gliomas through use of 11C-methionine-PET and physiological MRI in order to facilitate treatment decisions. Materials and methods: Patients with suspected low-grade glioma were prospectively and consecutively included after referral to the Neurosurgical Department, Uppsala University Hospital, between February 2010 and February 2014. All patients underwent morphological MRI, perfusion MRI, diffusion MRI and 11C-methionine PET. The institutional review board approved the study, and written informed consent was obtained prior to participation from each patient. Results: 11C-methionine PET hot spot regions corresponded spatially with regions of maximum relative cerebral blood volume in dynamic susceptibility contrast (DSC) perfusion MRI. The skewness of the transfer constantin dynamic contrast-enhanced (DCE) perfusion MRI, and the standard deviation of relative cerebral blood flow in DSC perfusion MRI could most efficiently discriminate between glioma grades II and III. In diffusion MRI, tumour fractional anisotropy differed between suspected low-grade gliomas of different neuropathological types. Quantitative diffusion tensor tractography was applicable for the evaluation of tract segment infiltration. Conclusion: PET and physiological MRI are able to characterise low-grade gliomas and are promising tools for guiding therapy and clinical decisions before neuropathological diagnosis has been obtained.

No description available.

Diffusion tensor imaging (DTI) is a structural magnetic resonance imaging (MRI) technique to record incoherent motion of water molecules and has been used to detect micro structural white matter alterations in clinical studies to explore certain brain disorders. A variety of DTI based techniques for detecting brain disorders and facilitating clinical group analysis have been developed in the past few years. However, there are two crucial issues that have great impacts on the performance of those algorithms. One is that brain neural pathways appear in complicated 3D structures which are inappropriate and inaccurate to be approximated by simple 2D structures, while the other involves the computational efficiency in classifying white matter tracts. The first key area that this dissertation focuses on is to implement a novel computing scheme for estimating regional white matter alterations along neural pathways in 3D space. The mechanism of the proposed method relies on white matter tractography and geodesic distance mapping. We propose a mask scheme to overcome the difficulty to reconstruct thin tract bundles. Real DTI data are employed to demonstrate the performance of the pro- posed technique. Experimental results show that the proposed method bears great potential to provide a sensitive approach for determining the white matter integrity in human brain. Another core objective of this work is to develop a class of new modeling and clustering techniques with improved performance and noise resistance for separating reconstructed white matter tracts to facilitate clinical group analysis. Different strategies are presented to handle different scenarios. For whole brain tractography reconstructed white matter tracts, a Fourier descriptor model and a clustering algorithm based on multivariate Gaussian mixture model and expectation maximization are proposed. Outliers are easily handled in this framework. Real DTI data experimental results show that the proposed algorithm is relatively effective and may offer an alternative for existing white matter fiber clustering methods. For a small amount of white matter fibers, a modeling and clustering algorithm with the capability of handling white matter fibers with unequal length and sharing no common starting region is also proposed and evaluated with real DTI data.

Over the past few years there has been an explosion of appetite for entrepreneurship, more particularly from women. Given the numerous barriers faced especially by women entrepreneurs today, there is a pressing need to initiate empowerment programmes to enable them to succeed in their endeavours. There is a need to empower women economically and to create employment opportunities and income generating activities to enable them to survive, prosper and provide support for their families. For the development of women–to–women business potential, women entrepreneurs require support in the form of training in strategic business development, access to credit funds, assistance with marketing skills and product design and development. Starting a firm of one's own may be one way for women to avoid the 'glass ceiling' that has sometimes been argued to exist in established organisations, providing one attractive way for entrepreneurial women to realise their full potential. Small business owners have more freedom to plan their personal schedules and to jungle them to suit their work and family demands which is often an important consideration for women. Entrepreneurs must be flexible and creative to meet the challenges which come along with running their businesses. The importance of a strong, entrepreneurial vision that can lead towards a successful enterprise is often underestimated. Women are disadvantaged by their lower levels of financial literacy and awareness. Access barriers are significant. Opportunities for financial services companies who can provide affordable, appropriate and accessible products to meet the needs of self–employed women are thus limited. Women entrepreneurs are still to overcome key challenges like access to training in international trade issues, operations management and marketing, as well as access to good mentors and mentorship programs. The study concludes that women confront barriers because of their gender and the author or investigator cites previous research that argues that these barriers are a result of socialisation practices, educational experiences, family roles, and networking. Government and all other relevant stakeholders should promote public awareness and ensure that resources for programs to foster entrepreneurship are decentralised. Women entrepreneurs should examine the role that the education system could play in developing entrepreneurial skills and attitudes. In Ekurhuleni region there is an increasing number of women who are required to steer their own businesses, and many are struggling to achieve success. This paper explores women entrepreneurship in the construction and engineering sectors. According to the responses obtained from the study, there are specific skills that entrepreneurs must posses in order to operate and succeed in construction and engineering industries within the Ekurhuleni region and these are communication skills, administration skills, financial skills and interpersonal skills. / Thesis (M.B.A.)--North-West University, Potchefstroom Campus, 2012.

Over the past few years there has been an explosion of appetite for entrepreneurship, more particularly from women. Given the numerous barriers faced especially by women entrepreneurs today, there is a pressing need to initiate empowerment programmes to enable them to succeed in their endeavours. There is a need to empower women economically and to create employment opportunities and income generating activities to enable them to survive, prosper and provide support for their families. For the development of women–to–women business potential, women entrepreneurs require support in the form of training in strategic business development, access to credit funds, assistance with marketing skills and product design and development. Starting a firm of one's own may be one way for women to avoid the 'glass ceiling' that has sometimes been argued to exist in established organisations, providing one attractive way for entrepreneurial women to realise their full potential. Small business owners have more freedom to plan their personal schedules and to jungle them to suit their work and family demands which is often an important consideration for women. Entrepreneurs must be flexible and creative to meet the challenges which come along with running their businesses. The importance of a strong, entrepreneurial vision that can lead towards a successful enterprise is often underestimated. Women are disadvantaged by their lower levels of financial literacy and awareness. Access barriers are significant. Opportunities for financial services companies who can provide affordable, appropriate and accessible products to meet the needs of self–employed women are thus limited. Women entrepreneurs are still to overcome key challenges like access to training in international trade issues, operations management and marketing, as well as access to good mentors and mentorship programs. The study concludes that women confront barriers because of their gender and the author or investigator cites previous research that argues that these barriers are a result of socialisation practices, educational experiences, family roles, and networking. Government and all other relevant stakeholders should promote public awareness and ensure that resources for programs to foster entrepreneurship are decentralised. Women entrepreneurs should examine the role that the education system could play in developing entrepreneurial skills and attitudes. In Ekurhuleni region there is an increasing number of women who are required to steer their own businesses, and many are struggling to achieve success. This paper explores women entrepreneurship in the construction and engineering sectors. According to the responses obtained from the study, there are specific skills that entrepreneurs must posses in order to operate and succeed in construction and engineering industries within the Ekurhuleni region and these are communication skills, administration skills, financial skills and interpersonal skills. / Thesis (M.B.A.)--North-West University, Potchefstroom Campus, 2012.

The aim of this thesis was to investigate the neural underpinnings of persistent developmental stuttering. We explored neural systems important for speech-motor integration and focused on subcortical control systems: the basal ganglia and cerebellum. A secondary aim of this work was to distinguish effects related to general traits of the disorder from those reflecting specific states of stuttered speech. To address these aims we used a variety of neuroimaging methodologies as well as an extensive neuropsychological and empirical test battery. Our examination of neural pathway microstructure using diffusion-tensor imaging replicated previous findings of widespread disorganisation of white matter in people who stutter. This disruption included all major white matter pathways leading in and out of the cerebellum. In our second, third, and fourth studies we examined functional activity at rest and during different types of speech. The brain networks used by people who stutter and controls largely overlapped. The brain regions that distinguished general traits and specific states of stuttering were somewhat task-specific. Subcortical activation in the basal ganglia and cerebellum was related to the frequency of dysfluent speech in the scanner. In our final study we examined performance on a variety of classical tasks of motor learning. We observed evidence of delayed learning in response to changes in environmental feedback in the stuttering group relative to controls. Within people who stutter, subgroups who differ according to heritability of the disorder may also differ in the balance of dopamine in the basal ganglia. Overall, we concluded that cerebellar alterations contribute to the general trait of stuttering, while basal ganglia disruption may reflect specific effects within stuttering. Our work supports a broader role of the subcortical system in speech production, generally.

O transtorno bipolar (TB) é uma das doenças psiquiátricas mais comuns e com altas taxas de morbimortalidade. Existe uma busca de um modelo neurofisiológico que poderia fornecer medidas objetivas para o diagnóstico desta doença, bem como fornecer parâmetros fisiológicos para monitorar a progressão, quantificar o dano causado pela mesma e prever a resposta ao tratamento na tentativa de direcionar a terapêutica adequada a cada estágio e evitar sua progressão. Kapczinski et al (2014) propôs um modelo de estadiamento do TB baseado em sintomas interepisódio, biomarcadores (inflamatórios e neuroplásticos) e dano cognitivo. Na última década, técnicas de neuroimagem e de genética proliferaram e vem se tornando promissoras ferramentas para se estabelecer a base de modelos neurofisiológicos do TB. Embora o prejuízo cognitivo já esteja bem descrito na literatura, o conhecimento sobre as alterações de conectividade em estudos de neuroimagem associadas a esta condição ainda é escasso. A atual pesquisa se propos a investigar os mecanismos fisiopatológicos do transtorno do humor bipolar com enfoque na substância branca (SB) cerebral. Primeiramente foi feita uma revisão sistemática da literatura internacional de estudos que correlacionaram o TB e estudo de tensor de difusão (DTI) por ressonância magnética (RM). Foram incluidos 18 trabalhos que fechavam com os critérios da pesquisa. Os trabalhos mostraram nas análises de DTI alterações na integridade da SB entre o os pacientes com TB em comparação com os controles normais. Essas alterações foram encontradas especialmente nos tratos de SB implicados em conectar uma ampla gama de redes neurais, incluindo as regiões estriatais ventrais e fronto-temporais. A maioria dos estudos mostrou valores de anisotropia fracionada (FA) reduzidos em tratos comissurais inter-hemisféricos e de associação frontolímbicos, com destaque para o corpo caloso que foi a estrutura mais acometida nos diferentes estudos. Estes achados são concordantes com a "síndrome de desconexão" que é encontrada em pacientes com TB. O segundo propósito desta tese foi fazer uma comparação dos volumes de substância branca total, do volume do corpo caloso e do volume total de substância cinzenta entre pacientes com TB em estagio inicial e avançado em relação aos seus respectivos controles normais pareados para sexo, idade, hemisfério dominante e nível de escolaridade. A análise de volumetria das estruturas corticais e subcorticais foi feita por meio de método de segmentação automatizada pelo software Freesurfer. Foram avaliados 55 sujeitos, sendo 29 pacientes com TB e 26 controles normais. A análise volumétrica encontrou redução da SB total e do volume do corpo caloso tanto em pacientes com TB no estagio inicial quanto tardio da doença. O volume de susbtância cinzenta (SC) total estava reduzido somente nos pacientes com TB em estágio tardio. Estes achados são inéditos na literatura e podem explicar a síndrome desconectiva dos pacientes com TB desde os estágios iniciais e o declínio cognitivo acentuado dos pacientes em estágios mais avançados da doença. Podem propor uma pista para achados de biomarcadores em populações em risco para desenvolver TB. / Bipolar disorder (BD) is one of the most common psychiatric disorders and with high morbidity and mortality rates. There is a search for a neurophysiological model that could provide objective measurements for diagnosis of this disease, as well as providing physiological parameters to monitor the progression, quantify the damage caused by it and predict response to treatment in an attempt to direct the appropriate therapy for each stage and prevent its progression. Kapczinski et al. (2014) proposed a staging BD model based on interepisode symptoms, biomarkers (inflammatory and neuroplastic) and cognitive impairment. In the last decade, techniques of neuroimaging and genetic proliferated and are becoming promising tools to settle the basis of neurophysiological models of BD. Although cognitive impairment is already well described in the literature, knowledge of the connectivity changes in neuroimaging studies associated with this condition is still scarce. Current research is proposed to investigate the pathophysiological mechanisms of bipolar disorder focusing on white matter (WM) brain. It was first made a systematic review of the literature studies that correlated the BD and diffusion tensor imaging (DTI). We found 18 published DTI studies that identified WM changes in subjects with bipolar disorder. The studies showed changes in the integrity of DTI WM between BD patients compared with normal controls. These changes were found especially in the treatment of WM connecting implicated in a wide range of neural networks, including ventral striatal regions and frontotemporal. Most studies showed reduced FA values in commissural inter-hemispheric and fronto-limbic association tracts, especially the corpus callosum which was the most affected structure in different studies. These findings are consistent with the "disconnection syndrome" which is found in patients with TB. The second purpose of this thesis was to compare the total white matter volume, the corpus callosum volume and total volume of gray matter in patients with BD in early and advanced stage in relation to their normal controls matched for sex, age, dominant hemisphere and education level. The volumetric analysis of cortical and subcortical structures was performed by automated segmentation method by FreeSurfer software. We evaluated 55 subjects, 29 BD patients and 26 normal controls. Volumetric analysis found reduced total WM and the corpus callosum volume both in BD patients at the early stage and late disease. The volume of total gray matter (GM) was reduced only in patients with late-stage BD. These findings are unprecedented in the literature and may explain the disconnection syndrome that is present in patients from the early stages and the marked cognitive decline of patients in more advanced stages of the disease. These findings may offer a clue to biomarker findings in populations at risk to develop BD.