Framework para a análise da microestrutura do corpo caloso ao longo de sua extensão

Orientador: Roberto de Alencar LotufoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: O corpo caloso é de grande interesse para a comunidade médica e de pesquisa, e suas características têm sido associadas a muitos distúrbios psicológicos e doenças cerebrais. A análise localizada de suas características é um procedimento usual, particularmente para o diagnóstico de esclerose múltipla e outras doenças inflamatórias. Neste trabalho, propomos um framework para extrair características da microestrutura ao longo da extensão do corpo caloso em uma função de assinatura, permitindo que análises globais e localizadas sejam realizadas no domínio 1--D da assinatura, em vez do domínio 3--D de a imagem original. Nossa solução é uma sucessão de vários métodos especializados, que foram projetados para resolver partes específicas do pipeline de geração de assinatura, incluindo a definição de um plano de simetria local para as fibras internas do corpo caloso, realizar a segmentação do corpo caloso, traçar o eixo médio da estrutura e extrair as características ao longo do eixo médio. Um dataset com imagens de 80 aquisições distintas de indivíduos saudáveis foi usado para avaliar tanto o plano de simetria da fibra quanto as assinaturas geradas. Os resultados mostram que o plano predito pelo nosso método é significativamente distinto dos planos preditos pelos métodos tradicionais de estimativa do plano sagital médio, com uma diferença maior na inclinação em relação ao plano axial, de cerca de 2 graus em média. As assinaturas apresentam um padrão similar na maioria dos casos, mas retêm características individuais. Em uma análise de agrupamento, verificamos que existe um único aglomerado maior que tem seu tamanho reduzido drasticamente apenas quando todas as arestas são removidas, exceto aquelas com pelo menos 90% de similaridade. As assinaturas geradas pelo nosso framework proposto fornecem uma maneira inédita de realizar a análise das características da microestrutura do corpo caloso, que é inerentemente localizada e independente da morfologia da estrutura. Nossa solução abre novas possibilidades no campo para pesquisa e desenvolvimento futuros relacionadosAbstract: The corpus callosum is of great interest for the medical and research community, and its characteristics have been associated with many psychological disorders and brain diseases. Localized analysis of its features is a usual procedure, particularly for the diagnosis of multiple sclerosis and other inflammatory diseases. In this work, we propose a framework for extracting microstructure features along the corpus callosum extent into a signature function, allowing global and localized analyses to be performed in the 1--D domain of the signature, instead of the 3--D domain of the original image. Our solution is a succession of several specialized methods, which were designed to solve specific parts of the signature generation pipeline, including defining a plane of local symmetry for the corpus callosum internal fibers, perform the corpus callosum segmentation, trace the structure median axis, and extract the features along the median axis. A dataset with images from 80 distinct acquisitions from healthy subjects was used to evaluate both, the fiber's symmetry plane, and the generated signatures. Results show that the plane predicted by our method is significantly distinct from the planes predicted by traditional mid--sagittal plane estimation methods, with a larger difference on the inclination relative to the axial plane, of about 2 degrees on average. The signatures present a similar pattern in most cases but retain individual characteristics. In a clustering analysis, we verified that there is one single larger cluster that has its size reduced dramatically only when all edges are removed, except for the ones with at least 90% of similarity. The signatures generated by our proposed framework provide an unprecedented way to perform the analysis of the corpus callosum microstructure features, which is inherently localized, and independent from the structure morphology. Our solution open new possibilities for future related research and development in the fieldDoutoradoEngenharia de ComputaçãoDoutor em Engenharia Elétrica2012/23059-8FAPES

AUTOMATIC 3D DEFORMED MIDSAGITTAL SURFACE LOCALIZATION BY CONSTRAINED MONTE CARLO OPTIMIZATION

AUTOMATIC 3D DEFORMED MIDSAGITTAL SURFACE LOCALIZATION BY CONSTRAINED MONTE CARLO OPTIMIZATIO

Employing Symmetry Features for Automatic Misalignment Correction in Neuroimages

A novel method to automatically compute the symmetry plane and to correct the 3D orientation of neuro-images is presented. In acquisition of neuroimaging scans, the lack of perfect alignment of a patient's head makes it challenging to evaluate brain images. By deploying a shape-based criterion, the symmetry plane is defined as a plane that best matches external surface points on one side of the head, with their counterparts on the other side. In our method, the head volume is represented as a re-parameterized surface point cloud, where each location is parameterized by its elevation (latitude), azimuth (longitude), and radius. The search for the best matching surfaces is implemented in a multi-resolution paradigm, and the computation time is significantly decreased. The algorithm was quantitatively evaluated using in both simulated data and in real T1, T2, Flair magnetic resonance patient images. This algorithm is found to be fast (< 10s per MR volume), robust and accurate (< .6 degree of Mean Angular Error), invariant to the acquisition noise, slice thickness, bias field, and pathological asymmetries

Towards the “Baby Connectome”: Mapping the Structural Connectivity of the Newborn Brain

Defining the structural and functional connectivity of the human brain (the human “connectome”) is a basic challenge in neuroscience. Recently, techniques for noninvasively characterizing structural connectivity networks in the adult brain have been developed using diffusion and high-resolution anatomic MRI. The purpose of this study was to establish a framework for assessing structural connectivity in the newborn brain at any stage of development and to show how network properties can be derived in a clinical cohort of six-month old infants sustaining perinatal hypoxic ischemic encephalopathy (HIE). Two different anatomically unconstrained parcellation schemes were proposed and the resulting network metrics were correlated with neurological outcome at 6 months. Elimination and correction of unreliable data, automated parcellation of the cortical surface, and assembling the large-scale baby connectome allowed an unbiased study of the network properties of the newborn brain using graph theoretic analysis. In the application to infants with HIE, a trend to declining brain network integration and segregation was observed with increasing neuromotor deficit scores

Brain structural and functional asymmetry in human situs inversus totalis

Magnetic resonance imaging was used to investigate brain structural and functional asymmetries in 15 participants with complete visceral reversal (situs inversus totalis, SIT). Language-related brain structural and functional lateralization of SIT participants, including peri-Sylvian gray and white matter asymmetries and hemispheric language dominance, was similar to those of 15 control participants individually matched for sex, age, education, and handedness. In contrast, the SIT cohort showed reversal of the brain (Yakovlevian) torque (occipital petalia and occipital bending) compared to the control group. Secondary findings suggested different asymmetry patterns between SIT participants with (n = 6) or without (n = 9) primary ciliary dyskinesia (PCD, also known as Kartagener syndrome) although the small sample sizes warrant cautious interpretation. In particular, reversed brain torque was mainly due to the subgroup with PCD-unrelated SIT and this group also included 55% left handers, a ratio close to a random allocation of handedness. We conclude that complete visceral reversal has no effect on the lateralization of brain structural and functional asymmetries associated with language, but seems to reverse the typical direction of the brain torque in particular in participants that have SIT unrelated to PCD. The observed differences in asymmetry patterns of SIT groups with and without PCD seem to suggest that symmetry breaking of visceral laterality, brain torque, and language dominance rely on different mechanisms

Thalamocortical Sensorimotor Circuit in Multiple Sclerosis: An Integrated Structural and Electrophysiological Assessment

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Form in Darkness: Linking Visual Cortex Structure With Spontaneous Neural Function

Spontaneous neural activity within visual cortex is synchronized at varying spatial scales, from the cytoarchitecural level of individual neurons to the coarse scale of whole regions. The neural basis of this synchronicity remains ambiguous. In this thesis, we focus on the role visual experience plays in organizing the spontaneous activity within the visual system. We start in Chapter 2 by creating a means by which to analyze homologous patches of cortex between sighted and blind individuals, as lack of vision precludes the use of traditional stimulus-driven mapping techniques. We find that anatomy alone could indeed predict the retinotopic organization of an individual\u27s striate cortex with an accuracy equivalent to the length of a typical mapping experiment. Chapter 3 applies this approach to analyze the organization of spontaneous signals within the striate cortex of blind and sighted subjects. We find that lack of visual experience produces a subtle change in the pattern of corticocortico correlations only between the hemispheres, and that these correlations are best modeled as function of cortical distance, not retinotopy. Chapter 4 expands our analysis to include areas V2 and V3. Here, we find that persistent visual experience supports network-level neural synchrony between spatially distributed cortical visual areas at both a coarse (regional) and fine (topographic) scale. Together, these results allow us model the organization of spontaneous activity in visual cortex as a combination of network signals linked to visual function and intrinsic signals coupled to structural connections. In the final chapter, we examine possible top-down mediators that may further modulate this network-level correlation. Minimal change in synchronicity is observed in a subject with a corpus callosotomy, suggesting the preeminence of bottom-up inputs. Taken together, this work advances our understanding of the origins of coherent spontaneous neural activity within visual cortex

Evalutation of fetal cerebral blood flow perfusion using three dimensional power doppler ultrasound angiography in fetuses affected by intrauterine growth retardation

The aim of the present study is to explore the possible use of 3D Power Doppler Angiography (3D-PDA) using VOCAL software (General Electric Healthcare, USA) in the assessment of different cerebral regions in normal and growth restricted fetuses (IUGR). This is a pilot study, that means a small experiment designed to test the method and gather information prior to a larger study.In Late Onset IUGR fetuses, presenting normal Bidimensional Doppler flow indices of umbilical and middle cerebral arteries, Vascularity Index (VI) and Vascular Flow Index (VFI) of the frontal zone of the fetal brain resulted increased demonstrating the \u201cfrontal brain sparing effect\u201d . On the other hand, these vascular parameters were decreased in the temporal zone suggesting a vascular redistribution during brain sparing effect according to a regional increase in bloody supply to the frontal region sprinkled mainly by the anterior cerebral artery. This shift may indicate that general cognitive functions, such as impulse control, language, memory, problem solving and socialization may be preferentially preserved suggesting a hierarchical order in the protection of the brain function

Action in Perception : Prominent Visuo-Motor Functional Symmetry in Musicians during Music Listening

Musical training leads to sensory and motor neuroplastic changes in the human brain. Motivated by findings on enlarged corpus callosum in musicians and asymmetric somatomotor representation in string players, we investigated the relationship between musical training, callosal anatomy, and interhemispheric functional symmetry during music listening. Functional symmetry was increased in musicians compared to nonmusicians, and in keyboardists compared to string players. This increased functional symmetry was prominent in visual and motor brain networks. Callosal size did not significantly differ between groups except for the posterior callosum in musicians compared to nonmusicians. We conclude that the distinctive postural and kinematic symmetry in instrument playing cross-modally shapes information processing in sensory-motor cortical areas during music listening. This cross-modal plasticity suggests that motor training affects music perception.Peer reviewe