6,608 research outputs found
Synthesizing pseudo-T2w images to recapture missing data in neonatal neuroimaging with applications in rs-fMRI
T1- and T2-weighted (T1w and T2w) images are essential for tissue classification and anatomical localization in Magnetic Resonance Imaging (MRI) analyses. However, these anatomical data can be challenging to acquire in non-sedated neonatal cohorts, which are prone to high amplitude movement and display lower tissue contrast than adults. As a result, one of these modalities may be missing or of such poor quality that they cannot be used for accurate image processing, resulting in subject loss. While recent literature attempts to overcome these issues in adult populations using synthetic imaging approaches, evaluation of the efficacy of these methods in pediatric populations and the impact of these techniques in conventional MR analyses has not been performed. In this work, we present two novel methods to generate pseudo-T2w images: the first is based in deep learning and expands upon previous models to 3D imaging without the requirement of paired data, the second is based in nonlinear multi-atlas registration providing a computationally lightweight alternative. We demonstrate the anatomical accuracy of pseudo-T2w images and their efficacy in existing MR processing pipelines in two independent neonatal cohorts. Critically, we show that implementing these pseudo-T2w methods in resting-state functional MRI analyses produces virtually identical functional connectivity results when compared to those resulting from T2w images, confirming their utility in infant MRI studies for salvaging otherwise lost subject data
Automated Extraction of Biomarkers for Alzheimer's Disease from Brain Magnetic Resonance Images
In this work, different techniques for the automated extraction of biomarkers for
Alzheimer's disease (AD) from brain magnetic resonance imaging (MRI) are proposed.
The described work forms part of PredictAD (www.predictad.eu), a joined
European research project aiming at the identification of a unified biomarker for AD
combining different clinical and imaging measurements. Two different approaches are
followed in this thesis towards the extraction of MRI-based biomarkers: (I) the extraction
of traditional morphological biomarkers based on neuronatomical structures
and (II) the extraction of data-driven biomarkers applying machine-learning techniques.
A novel method for a unified and automated estimation of structural volumes
and volume changes is proposed. Furthermore, a new technique that allows the low-dimensional
representation of a high-dimensional image population for data analysis
and visualization is described. All presented methods are evaluated on images from
the Alzheimer's Disease Neuroimaging Initiative (ADNI), providing a large and diverse
clinical database. A rigorous evaluation of the power of all identified biomarkers to
discriminate between clinical subject groups is presented. In addition, the agreement
of automatically derived volumes with reference labels as well as the power of the
proposed method to measure changes in a subject's atrophy rate are assessed. The
proposed methods compare favorably to state-of-the art techniques in neuroimaging
in terms of accuracy, robustness and run-time
Aju plastilisus ja võrgustike reorganiseerumine perinataalset insulti põdenud lastel: funktsionaalne magnetresonantstomograafiline uuring
Väitekirja elektrooniline versioon ei sisalda publikatsiooneViimastel aastakümnetel on arstide, aga ka elanikkonna teadlikkus tõusnud, et insult võib esineda kogu elu jooksul, ka lastel. Eriti suur insuldi tõenäosus on vastsündinueas, umbes üks tuhande elussünni kohta. Insult vastsündinueas võib kaasa tuua elukestva motoorse, kognitiivse kahjustuse ning epilepsia, lisanduda võivad käitumishäired ja sotsiaalne puue. Vastsündinuea insult mõjutab väga pika aja jooksul lisaks lastele ka nende lähedasi, tuues kaasa stressi ja depressiooni kogu perele, ning koormab majanduslikult tervet ühiskonda.
Vastsündinuea insuldi järgne ajukahjustus on olenevalt tekkemehhanismist ja suurusest erinev, ka laste areng ja oskused on sellest tulenevalt erinevad. Õnneks on laste aju arenev ja plastiline ning suudab vähemalt osa ajukahjustustest võrreldes täiskasvanutega paremini kompenseerida. Kuna insult on harvaesinev ja kahjustus varieeruv, on teadmised vastsündinuea insuldi kohta piiratud.
Uurimistöö eesmärk oli uurida vastsündinuea insuldiga laste aju võimet võrreldes tervete lastega kahjustust erinevate kahjustuse tüüpide ja ulatuste puhul kompenseerida. Me kasutasime erinevaid magnetresonantstomograafilisi (MRT) uuringuid koos pilditöötlusega, et leida tunnuseid, mille abil oleks võimalik juba esimestel eluaastatel ennustada insuldiga laste kognitiivseid ja motoorseid võimeid ja paremini planeerida taastusravi.
Uuringu tulemused näitasid vastsündinuea insuldiga laste motoorsete ja kognitiivsete võimete ning aju ümberorganiseerumise seost kahjustuse ulatuse ja tüübiga. Muutused insuldiga vastsündinu ajus aitavad kompenseerida ja vähendada kahjustuse mõju, kuid ei suuda täielikult tagada eakohast arengut.
Uuringus saadud teadmisi aju plastilisuse ja ümberorganiseerumisvõime kohta on võimalik rakendada lisaks insuldihaigetele ka teiste ajukahjustusega (nt trauma, ajukasvaja või epilepsia) laste puhul. Need teadmised täiendavad vastsündinuea insuldi laste radioloogilistest uuringutest saadavat teavet, rõhutades nende vajalikkust.Stroke can occur during the entire lifetime and is probably underdiagnosed in children. In perinatal period the risk of stroke is especially high, about 1:1000 live births. Perinatal stroke may lead to various motor and cognitive impairments and epilepsy. Perinatal stroke causes lifelong physical, mental and emotional disabilities and social burden not only to children, but also to their families along with an economic burden to the society.
Perinatal stroke is a heterogonous condition, with different brain lesions depending on the vascular type of stroke leading to different outcomes. Children’s brain is plastic and able to reorganize and at least partly compensate for damage after stroke. However, the knowledge of perinatal stroke is still limited due to the low prevalence and inherent heterogeneity of damage.
The aim of the study was to investigate brain’s ability to reorganize in different vascular types of perinatal stroke compared to healthy controls and to evaluate how it affects the motor, cognitive and language outcomes. Various radiological markers for predicting motor, cognitive and language outcome in children with perinatal stroke were identified using functional magnetic resonance imaging and volumetric image analysis.
The study showed that motor, cognitive and language outcomes in children with perinatal stroke correlates with vascular type and extent of stroke lesion. The brain’s plasticity and reorganization abilities were shown to only minimize the negative effect of large stroke lesions, but not to ensure entirely normal outcome.
The knowledge of brain plasticity and reorganization in perinatal stroke children can be generalized to cases involving other focal brain damages, like trauma, tumors and epilepsy. The study accentuates the importance of radiological investigation of children with perinatal stroke and enhances the value of radiological evaluation.https://www.ester.ee/record=b551935
Multimodality evaluation of the pediatric brain: DTI and its competitors
The development of the human brain, from the fetal period until childhood, happens in a series of intertwined neurogenetical and histogenetical events that are influenced by environment. Neuronal proliferation and migration, cell aggregation, axonal ingrowth and outgrowth, dendritic arborisation, synaptic pruning and myelinisation contribute to the ‘plasticity of the developing brain'. These events taken together contribute to the establishment of adult-like neuroarchitecture required for normal brain function. With the advances in technology today, mostly due to the development of non-invasive neuroimaging tools, it is possible to analyze these structural events not only in anatomical space but also longitudinally in time. In this review we have highlighted current ‘state of the art' neuroimaging tools. Development of the new MRI acquisition sequences (DTI, CHARMED and phase imaging) provides valuable insight into the changes of the microstructural environment of the cortex and white matter. Development of MRI imaging tools dedicated for analysis of the acquired images (i) TBSS and ROI fiber tractography, (ii) new tissue segmentation techniques and (iii) morphometric analysis of the cortical mantle (cortical thickness and convolutions) allows the researchers to map the longitudinal changes in the macrostructure of the developing brain that go hand-in-hand with the acquisition of cognitive skills during childhood. Finally, the latest and the newest technologies, like connectom analysis and resting state fMRI connectivity analysis, today, for the first time provide the opportunity to study the developing brain through the prism of maturation of the systems and networks beyond individual anatomical areas. Combining these methods in the future and modeling the hierarchical organization of the brain might ultimately help to understand the mechanisms underlying complex brain structure function relationships of normal development and of developmental disorder
Synergy of image analysis for animal and human neuroimaging supports translational research on drug abuse
pre-printThe use of structural magnetic resonance imaging (sMRI) and diffusion tensor imaging (DTI) in animal models of neurophysiology is of increasing interest to the neuroscience community. In this work, we present our approach to create optimal translational studies that include both animal and human neuroimaging data within the frameworks of a study of post-natal neuro-development in intra-uterine cocaine-exposure. We propose the use of non-invasive neuroimaging to study developmental brain structural and white matter pathway abnormalities via sMRI and DTI, as advanced MR imaging technology is readily available and automated image analysis methodology have recently been transferred from the human to animal imaging setting. For this purpose, we developed a synergistic, parallel approach to imaging and image analysis for the human and the rodent branch of our study. We propose an equivalent design in both the selection of the developmental assessment stage and the neuroimaging setup. This approach brings significant advantages to study neurobiological features of early brain development that are common to animals and humans but also preserve analysis capabilities only possible in animal research. This paper presents the main framework and individual methods for the proposed cross-species study design, as well as preliminary DTI cross-species comparative results in the intra-uterine cocaine-exposure study
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