Dissertations / Theses: 'Neurology; Magnetic resonance imaging'

1

Wylie, Glenn Richard. "Priming and shifting of task set." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301728.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Rutherford, Mary. "Magnetic resonance imaging of hypoxic-ischaemic brain lesions in the term infant." Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262817.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Brooks, Jonathan Charles William. "Quantification of magnetic resonance spectra using imaging based techniques : application to the study of brain ageing." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367141.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Reddy, H. "Cortical re-organisation of plasticity : applying fMRI to study disease." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365777.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Petrovic, Aleksandar. "Connectivity driven registration of magnetic resonance images of the human brain." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:fd95c6d4-06d2-41b4-b6f2-5cbd73cb83a9.

Full text

Abstract:

Image registration methods underpin many analysis techniques in neuroimaging. They are essential in group studies when images of different individuals or different modalities need to be brought into a common reference frame. This thesis explores the potential of brain connectivity- driven alignment and develops surface registration techniques for magnetic resonance imaging (MRI), which is a noninvasive neuroimaging tool for probing function and structure of the human brain. The first part of this work develops a novel surface registration framework, based on free mesh deformations, which aligns cortical and subcortical surfaces by matching structural connectivity patterns derived using probabilistic tractography (diffusion-weighted MRI). Structural, i.e. white matter, connectivity is a good predictor of functional specialisation and structural connectivity-driven registration can therefore be expected to enhance the alignment of functionally homologous areas across subjects. The second part validates developed methods for cortical surfaces. Resting State Networks are used in an innovative way to delineate several functionally distinct regions, which were then used to quantify connectivity-driven registration performance by measuring the inter- subject overlap before and after registration. Consequently, the proposed method is assessed using an independent imaging modality and the results are compared to results from state-of-the-art cortical geometry-driven surface registration methods. A connectivity-driven registration pipeline is also developed for, and applied to, the surfaces of subcortical structures such as the thalamus. It is carefully validated on a set of artificial test examples and compared to another novel surface registration paradigm based on spherical wavelets. The proposed registration pipeline is then used to explore the differences in the alignment of two groups of subjects, healthy controls and Alzheimer's disease patients, to a common template. Finally, we propose how functional connectivity can be used instead of structural connectivity for driving registrations, as well as how the surface-based framework can be extended to a volumetric one. Apart from providing the benefits such as the improved functional alignment, we hope that the research conducted in this thesis will also represent the basis for the development of templates of structural and functional brain connectivity.

APA, Harvard, Vancouver, ISO, and other styles

6

Beckwith, Travis J. "A Magnetic Resonance Imaging Study of the Developmental Consequences of Childhood Lead Exposure in Adulthood." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439309120.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Okell, Thomas William. "Assessment of collateral blood flow in the brain using magnetic resonance imaging." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:7e63bcf2-22bf-49e5-81ec-1644217605ae.

Full text

Abstract:

Collateral blood flow is the compensatory flow of blood to the tissue through secondary channels when the primary channel is compromised. It is of vital importance in cerebrovascular disease where collateral flow can maintain large regions of brain tissue which would otherwise have suffered ischaemic damage. Traditional x-ray based techniques for visualising collateral flow are invasive and carry risks to the patient. In this thesis novel magnetic resonance imaging techniques for performing vessel-selective labelling of brain feeding arteries are explored and developed to reveal the source and extent of collateral flow in the brain non-invasively and without the use of contrast agents. Vessel-encoded pseudo-continuous arterial spin labelling (VEPCASL) allows the selective labelling of blood water in different combinations of brain feeding arteries that can be combined in post-processing to yield vascular territory maps. The mechanism of VEPCASL was elucidated and optimised through simulations of the Bloch equations and phantom experiments, including its sensitivity to sequence parameters, blood velocity and off-resonance effects. An implementation of the VEPCASL pulse sequence using an echo-planar imaging (EPI) readout was applied in healthy volunteers to enable optimisation of the post-labelling delay and choice of labelling plane position. Improvements to the signal-to-noise ratio (SNR) and motion-sensitivity were made through the addition of background suppression pulses and a partial-Fourier scheme. Experiments using a three-dimensional gradient and spin echo (3D-GRASE) readout were somewhat compromised by significant blurring in the slice direction, but showed potential for future work with a high SNR and reduced dropout artefacts. The VEPCASL preparation was also applied to a dynamic 2D angiographic readout, allowing direct visualisation of collateral blood flow in the brain as well as a morphological and functional assessment of the major cerebral arteries. The application of a balanced steady-state free precession (bSSFP) readout significantly increased the acquisition efficiency, allowing the generation of dynamic 3D vessel-selective angiograms. A theoretical model of the dynamic angiographic signal was also derived, allowing quantification of blood flow through specified vessels, providing a significant advantage over qualitative x-ray based methods. Finally, these methods were applied to a number of patient groups, including those with vertebro-basilar disease, carotid stenosis and arteriovenous malformation. These preliminary studies demonstrate that useful clinical information regarding collateral blood flow can be obtained with these techniques.

APA, Harvard, Vancouver, ISO, and other styles

8

Riley, Amanda L. "Effectiveness of Fluorogold Bound Conjugate in Imaging Mice Neuroendocrine Circuits." Kent State University Honors College / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1587996298161636.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Tziortzi, Andri. "Quantitative dopamine imaging in humans using magnetic resonance and positron emission tomography." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:26b8b4c2-0237-4c40-8c84-9ae818a0dabf.

Full text

Abstract:

Dopamine is an important neurotransmitter that is involved in several human functions such as reward, cognition, emotions and movement. Abnormalities of the neurotransmitter itself, or the dopamine receptors through which it exerts its actions, contribute to a wide range of psychiatric and neurological disorders such as Parkinson’s disease and schizophrenia. Thus far, despite the great interest and extensive research, the exact role of dopamine and the causalities of dopamine related disorders are not fully understood. Here we have developed multimodal imaging methods, to investigate the release of dopamine and the distribution of the dopamine D2-like receptor family in-vivo in healthy humans. We use the [¹¹C]PHNO PET ligand, which enables exploration of dopamine-related parameters in striatal regions, and for the first time in extrastriatal regions, that are known to be associated with distinctive functions and disorders. Our methods involve robust approaches for the manual and automated delineation of these brain regions, in terms of structural and functional organisation, using information from structural and diffusion MRI images. These data have been combined with [¹¹C]PHNO PET data for quantitative dopamine imaging. Our investigation has revealed the distribution and the relative density of the D3R and D2R sites of the dopamine D2-like receptor family, in healthy humans. In addition, we have demonstrated that the release of dopamine has a functional rather than a structural specificity and that the relative densities of the D3R and D2R sites do not drive this specificity. We have also shown that the dopamine D3R receptor is primarily distributed in regions that have a central role in reward and addiction. A finding that supports theories that assigns a primarily limbic role to the D3R.

APA, Harvard, Vancouver, ISO, and other styles

10

Zamboni, Giovanna. "Structural and functional magnetic resonance imaging (MRI) in the prediction and characterization of mild cognitive impairment (MCI) and Alzheimer's disease (AD)." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:8cdd8320-1243-4f85-928c-b03fd4bd1201.

Full text

Abstract:

The aim of the research presented in this thesis was to improve the characterisation of the changes in brain structure and function that occur at different stages of Alzheimer’s disease (AD) progression, from pre-symptomatic AD, to mild cognitive impairment (MCI), to clinically evident dementia, using magnetic resonance imaging (MRI) techniques. Baseline structural MRI data from a cohort of healthy older adults who were followed prospectively for ten years, during which time some developed MCI and some AD, were analysed. It was found that structural MRI could detect volume loss in medial-temporal lobes up to 7-10 years before clinical symptoms of AD appear. In addition, volumetric variability of medial-temporal regions detected by structural MRI across cognitively healthy older adults correlated with their performance on a task of visuospatial associative memory, and functional activation of the same regions occurred during successful performance of the same task on functional MRI (fMRI). Three groups of participants - cognitively healthy controls, people with MCI, and patients with probable AD - were then recruited and underwent a multimodal MRI protocol, which included functional sequences acquired at rest and during the execution of two different cognitive tasks (visuospatial associative memory and self-appraisal). Cross-sectional comparisons showed: (i) that successful visuospatial associative memory performance was associated with increased functional activity (measured with task fMRI) in lateral prefrontal regions in AD patients relative to controls and (ii) that increased functional activity overlapped with frontal brain networks showing increased functional connectivity (measured with resting fMRI) in the same AD patients. Further, by demonstrating group- and condition-specific decreased frontal activity in AD patients relative to controls during a self-appraisal fMRI task, it was shown the specific utility of fMRI to unravel cognitive mechanisms underlying specific neuropsychological symptoms such as unawareness of cognitive impairment (anosognosia) in MCI and AD. In conclusion, structural MRI can detect morphological changes in the preclinical stage of AD, possibly earlier than previously described, and these reliably match cognitive functioning in older adults. In the MCI and AD stages, once symptoms of cognitive impairment are clinically evident and measurable, task-related and resting functional MRI can inform on residual brain function detectable over and above the known changes in brain morphology and cognitive performance that have already occurred at these stages, emerging as a sensitive marker of residual ability that could potentially be used to measure the effect of new treatments.

APA, Harvard, Vancouver, ISO, and other styles

11

Hoepfner, Erika Barba-Müller. "Morphologic brain changes induced by pregnancy. A longitudinal magnetic resonance imaging study." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/319448.

Full text

Abstract:

En los seres humanos, la supervivencia del infante depende de forma considerable de los esfuerzos de la madre y la calidad de su cuidado contribuirá significativamente al desarrollo neurobiológico, cognitivo y socio-emocional del niño (Shonkoff et al., 2012). Además, casi todas las mujeres experimentarán un embarazo a lo largo de su vida, lo cual es reconocido por predisponer a la madre a cierta vulnerabilidad mental (Brunton and Russell, 2008). Sin embargo, se sabe muy poco sobre los efectos del embarazo en el cerebro de la mujer. Cambios endocrinos menos extremos ocasionan modificaciones morfológicas cerebrales (Erickson et al., 2010; Woolley and McEwen, 1993, 1992) y diversos estudios en mamíferos demuestran adaptaciones neuronales con el fin de garantizar el embarazo, el parto y el puerperio, lo cual que sugiere una plasticidad cerebral inherente a la reproducción en los seres humanos (Brunton and Russell, 2008; Kinsley and Amory-Meyer, 2011; Swain et al., 2014). Aunque esta cuestión se ha abordado previamente evaluando cambios a nivel cerebral global, los resultados aquí presentes son los primeros en revelar las características precisas de los cambios morfológicos cerebrales asociados a la reproducción exitosa en las madres humanas. El objetivo de este estudio es examinar en mujeres si el embarazo se asocia con cambios morfológicos cerebrales y en qué áreas. Se trata de un estudio longitudinal de casos y controles, donde obtuvimos imágenes de alta resolución mediante resonancia magnética del cerebro de 25 mujeres primíparas y sus parejas masculinas (n = 19) en dos momentos: antes y después del embarazo. También se adquirieron exploraciones longitudinales de 20 mujeres nulíparas controles y sus parejas masculinas (n = 17). Se aplicó un análisis morfométrico longitudinal basado en vóxeles para calcular los cambios en la sustancia gris (SG) entre los dos momentos de medición a nivel individual y posteriormente comparar estos cambios entre los grupos de sujetos (primíparas versus controles). Las comparaciones entre grupos revelan un patrón simétrico y altamente significativo de reducciones volumétricas de SG en las mujeres que pasaron por un embarazo en comparación con las mujeres control nulíparas. No se encontraron diferencias significativas entre las muestras masculinas. Estas reducciones de volumen de SG asociadas al embarazo se observan en la línea media posterior (cingulado posterior y precuneus), la corteza frontal medial (córtex prefrontal medial y cingulado anterior), la corteza prefrontal lateral bilateral (clústeres en la corteza prefrontal ventrolateral y dorsolateral) y la corteza temporal bilateral (surco temporal superior bilateral que se extiende a secciones laterales circundantes así como a estructuras temporales mediales tales como el giro fusiforme). Todos los valores de p son inferiores a 0,05 con corrección familywise-error. Los cambios son muy consistentes a través de la muestra y el total de las mujeres participantes pueden ser clasificadas de forma significativamente acertada en haber tenido un embarazo o no en base a la distribución de la SG en el cerebro. Los resultados aquí presentes son los primeros en demostrar que el embarazo está relacionado a cambios morfológicos cerebrales específicos en los seres humanos, proporcionando conocimientos primarios sobre la forma en que el cerebro de la mujer es modificado durante el embarazo. Los resultados se discuten a la luz de estudios que evalúan las áreas cerebrales implicadas y los posibles mecanismos neurobiológicos subyacentes a estas reducciones de volumen de SG. Aunque el mecanismo y el significado fisiológico de estos hallazgos son especulativos en la actualidad, este estudio proporciona claves primordiales sobre la base neural de la maternidad, la salud mental perinatal y la plasticidad cerebral en general.
In humans, the survival of the young is dependent to a significant degree on the exertions of the mother, and the quality of her care will contribute to the foundation of the infant’s neurobiological, cognitive and socio-emotional development (Shonkoff et al., 2012). Furthermore, almost every women will experience pregnancy which is recognized to predispose the mother to a period of mental vulnerability (Brunton and Russell, 2008). Nevertheless, very little is known on how pregnancy affects the human brain. It has been proven that less extreme endocrine changes render morphological brain modifications (Erickson et al., 2010; Woolley and McEwen, 1993, 1992) and several studies in mammals show adaptations in various brain systems in order to ensure pregnancy, delivery and postnatal care, suggesting in humans a brain plasticity inherent to reproduction itself (Brunton and Russell, 2008; Kinsley and Amory-Meyer, 2011; Swain et al., 2014). Although this question has been previously addressed assessing whole brain changes in size (Oatridge et al., 2002), the current findings are the first to explicitly show the precise morphologic brain changes associated with successful reproduction in human mothers. The aim of this study is to examine whether pregnancy is associated with morphological brain changes in women. In this longitudinal case-control study, we obtained high-resolution brain MRI scans of 25 primiparous women and their male partners (n=19) before and after pregnancy. Longitudinal scans of 20 nulliparous control women and their male partners (n=17) were also acquired. A longitudinal voxel based morphometric analysis was applied to calculate changes in grey matter (GM) between the two different time-points and compare these changes between the groups of subjects (primiparous versus controls). Group comparisons of these within-subject GM changes indicate a symmetrical pattern of highly significant GM volumetric reductions in the women who underwent pregnancy in comparison to the nulliparous control women. The comparison between the male samples does not yield significant differences. These GM volume reductions associated with pregnancy are observed in the posterior midline (posterior cingulate and precuneus), the medial frontal cortex (medial prefrontal cortex and anterior cingulate), bilateral lateral prefrontal cortex (clusters in the ventrolateral and dorsolateral prefrontal cortex) and bilateral temporal cortex (bilateral superior temporal sulcus extending to surrounding lateral temporal sections as well as medial temporal structures such as the fusiform gyrus). All p values are below 0.05 familywise-error corrected. The changes are remarkably consistent across subjects and the women can significantly be classified as having undergone pregnancy or not, based on the distribution of GM changes across the brain. The current findings are the first to demonstrate that pregnancy is related to specific morphological brain changes in humans, providing primary insights into the way a woman’s brain is modified during pregnancy. The results are discussed in the light of studies assessing the implicated brain areas and the potential neurobiological mechanisms underlying these GM volume reductions. Although the mechanism and physiological meaning of these findings are speculative at the present time, these findings provide primary clues regarding the neural basis of motherhood, perinatal mental health and brain plasticity in general.

APA, Harvard, Vancouver, ISO, and other styles

12

Cabezas, Grebol Mariano. "Atlas-based segmentation of multiple sclerosis lesions in magnetic resonance imaging." Doctoral thesis, Universitat de Girona, 2013. http://hdl.handle.net/10803/119608.

Full text

Abstract:

This thesis deals with the segmentation of brain magnetic resonance imaging applied to multiple sclerosis patients. This disease is characterised by the presence of white matter lesions in this image modality. After a thorough analysis of the state-of-the-art on this topic, pointing out the importance of prior knowledge, and a subsequent review of atlas-based segmentation of brain imaging, we propose two different multiple sclerosis lesion segmentation pipelines based on the conclusions of these studies. The first one provides an initial tissue classification using a modified expectation-maximisation algorithm, which is later on refined with a lesion segmentation step based on thresholding and a regionwise false positive reduction approach. The second one focuses only on the segmentation of lesions and uses an ensemble classifier alongside a rich feature pool including image intensities, probabilistic atlas maps, an outlier map and contextual information. Both approaches are tested against a novel database comprising imaging data from three different hospitals with a variable lesion load per case. The evaluation, carried out in a quantitative and qualitative manner, includes a comparison and uses several metrics for detection and segmentation. The analysis of the results points out a better performance relative to state-of-the-art approaches, with a clear improvement on the first pipeline in terms of detection, and a clear improvement on the second pipeline in terms of segmentation
Aquesta tesi es centra en la segmentació de imatges de ressonància magnètica del cervell aplicada a pacients d'esclerosi múltiple. Aquesta malaltia es caracteritza per l'aparició de lesions de matèria blanca, visibles en aquesta modalitat d'imatge. Després d'un anàlisi exhaustiu de l'estat de l'art en aquest tòpic, remarcant la importància de la informació prèvia, i també de la segmentació basada en atles del cervell, proposem dues estratègies diferents per a la segmentació de lesions basades en les conclusions d'ambdós estudis. La primera proporciona una classificació inicial dels teixits mitjançant una extensió de l'algorisme d'esperança-maximització, que es refina posteriorment amb un procés de segmentació de les lesions basat en una binarització inicial i una conseqüent estratègia de reducció de falsos positius a nivell de regió. La segona proposta es focalitza bàsicament en la segmentació de lesions i utilitza una combinació de classificadors febles entrenats amb un ric conjunt de característiques que inclou imatges d'intensitat, mapes probabilístics provinents d'un atles, un mapa d'intensitats atípiques i informació contextual. Ambdues estratègies han estat provades amb una nova base de dades formada per imatges de tres hospitals diferents amb diferent càrrega lesional per cas. L'avaluació d'aquestes proves, que s'ha dut a terme de forma quantitativa i qualitativa, inclou una comparativa i utilitza diferents mètriques de detecció i segmentació. L'anàlisi d'aquests resultats apunta a un millor rendiment relatiu a l'estat de l'art actual, amb una millor detecció per part de la primera estratègia i una millor segmentació per part de la segona

APA, Harvard, Vancouver, ISO, and other styles

13

Brown, Andrew Peter. "Imaging neuroinflammatory processes with USPIO-MRI." Thesis, University of Oxford, 2009. http://ora.ox.ac.uk/objects/uuid:aa1b5add-6a05-44ff-a270-5c31630f6577.

Full text

Abstract:

This thesis examines the utility of USPIO-MRI to provide a tool of tracking macrophage recruitment to sites of neuroinflammation within the CNS. Recruited macrophages and microglia resident in CNS tissue play a key role in the pathophysiology of a number of neuroinflammatory diseases such as neuropathic pain and multiple sclerosis. Under activated conditions, microglia and macrophages will phagocytose invading cells and CNS debris. It has been shown that ultrasmall superparamagnetic particles of iron oxide (USPIO), such as Sinerem, injected systemically, are engulfed by macrophages, which in turn migrate to sites of tissue injury. USPIOs can be visualised as a distinct reduction in signal intensity on T2* weighted MR images. However, there are still some issues regarding the distinction between iron-laden recruited macrophages and the entry of free iron across a permeable blood brain barrier (BBB) in disease cases. Hence, it was shown that intravenously injected Sinerem is cleared from the peripheral circulation within 24 hours, indentifying this as a time point as suitable for MCP-1 injection. Data showed that free USPIO can be visualised in the brain and that there is a linear relationship between Sinerem concentration and T2* signal intensity changes. MCP-1 induces macrophage recruitment to the site of microinjection and causes BBB breakdown at between 3 and 4 hours. In particular it was shown that T2* signal intensity changes are seen, in the presence of an intact BBB, as a result of Sinerem laden macrophages. This finding was verified by the co-localisation of ED-1 positive cells and Prussian blue positive regions. It was demonstrated that there is a strong correlation between T2* signal changes and the number of macrophages. This demonstrates that USPIO-MRI can be used to characterise macrophage infiltration in neuroinflammation in the presence of an intact BBB.

APA, Harvard, Vancouver, ISO, and other styles

14

Varsou, Ourania. "Neuroimaging of patients with acute focal neurological symptoms : investigating new functional and structural Magnetic Resonance Imaging measures." Thesis, University of Aberdeen, 2014. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=225771.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Brown, Christopher A. "THE DEFAULT MODE NETWORK AND EXECUTIVE FUNCTION: INFLUENCE OF AGE, WHITE MATTER CONNECTIVITY, AND ALZHEIMER’S PATHOLOGY." UKnowledge, 2017. http://uknowledge.uky.edu/neurobio_etds/18.

Full text

Abstract:

The default mode network (DMN) consists of a set of interconnected brain regions supporting autobiographical memory, our concept of the self, and the internal monologue. These processes must be maintained at all times and consume the highest amount of the brain’s energy during its baseline state. However, when faced with an active, externally-directed cognitive task, the DMN shows a small, but significant, decrease in activity. The reduction in DMN activity during the performance of an active, externally-directed task compared to a baseline state is termed task-induced deactivation (TID), which is thought to ‘free-up’ resources required to respond to external demands. However, older adults show a reduced level of TID in the DMN. Recently, it has begun to be appreciated that this decrease in TID may be associated with poorer cognitive performance, especially during tasks placing high demands on executive function (EF). Diminished DMN TID has not only been associated with increasing age but also with multiple age-related neurobiological correlates such as accumulating Alzheimer’s disease (AD) pathology and reductions in white matter (WM) connectivity. However, these biological factors—age, WM connectivity reductions and increasing AD pathology—are themselves related. Based on the literature, we hypothesized that declining WM connectivity may represent a common pathway by which both age and AD pathology contribute to diminished DMN TID. Further, we hypothesized that declines in DMN function and WM connectivity would predict poorer in EF. Three experiments were carried out to test these hypotheses. Experiment 1 tested whether WM connectivity predicted the level of DMN TID during a task requiring a high level of EF. Results from 117 adults (ages 25-83) showed that WM connectivity declined with increasing age, and that this decline in WM connectivity was directly associated with reduced DMN TID during the task. Experiment 2 tested whether declines in WM connectivity explained both age-related and AD pathology-related declines in DMN TID. Results from 29 younger adults and 35 older adults showed that declining WM connectivity was associated with increasing age and AD pathology, and that this decline in WM connectivity was a common pathway for diminished DMN TID associated with either aging or AD pathology. Experiment 3 investigated whether measures of WM connectivity and DMN TID at baseline could predict EF measured using clinically-used tests. Results from 29 older adults from Experiment 2 showed that less DMN TID predicted poorer EF at baseline and diminished WM connectivity at baseline predicted a greater decline in EF after 3 years. Further, WM connectivity explained reductions in EF predicted by baseline AD pathology, as well as further reductions in EF not predicted by baseline AD pathology. Together the results of these studies suggest that WM connectivity is a key pathway for age-related and AD pathology-related patterns of diminished DMN TID associated with poorer EF. Further, WM connectivity may represent a potential therapeutic target for interventions attempting to prevent future declines in EF occurring in aging and AD.

APA, Harvard, Vancouver, ISO, and other styles

16

Centeno, Soladana Maria. "Magnetic resonance imaging in epilepsy. Functional and structural imaging in frontal lobe epilepsy and language study in bilingual patients." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/386529.

Full text

Abstract:

Gracias al desarrollo de las técnicas de neuroimagen en las últimas décadas se han conseguido avances importantes en el conocimiento de la epilepsia y sus mecanismos; descubriéndose cuestiones calves que han modificado conceptos clásicos y generado nuevas hipótesis en este campo. En los trabajos que componen esta tesis doctoral se utiliza como herramienta común la resonancia magnética para investigar varios aspectos que comprenden desde la función cognitiva a aspectos estructurales. En concreto se han empleado técnicas de resonancia magnética funcional y análisis cuantitativo de imagen estructural para responder a las hipótesis planteadas en los distintos trabajos que la conforman. La tesis comprende tres estudios: los dos primeros se centran en la epilepsia frontal y el tercero en mapeo de lenguaje pacientes bilingües con epilepsia. La epilepsia frontal (EF) es el segundo síndrome más prevalente dentro de las epilepsias focales, después de la epilepsia temporal. Sin embargo, debido a su complejidad como grupo, existen pocos estudios concluyentes a cerca de la función cognitiva en estos pacientes. Tampoco se conocen los cambios funcionales en las redes cognitivas que subyacen los déficits cognitivos en este grupo. Comprender estos aspectos contribuiría de manera importante a entender los déficits cognitivos en este grupo así como a comprender las alteraciones causadas por la cirugía. El primer trabajo de esta tesis estudia la memoria a largo plazo en pacientes con EF. Existen datos contradictorios sobre los déficits de memoria en pacientes con EF. Esta función ha sido poco explorada a pesar de la prevalencia de problemas de memoria en este grupo. Utilizando un paradigma de memoria en resonancia magnética funcional se caracterizaron los cambios funcionales secundarios a la epilepsia frontal y las alteraciones que se asocian al deterioro de esta función. En el segundo trabajo sobre epilepsia frontal se explora la presencia de cambios estructurales en sustancia gris en pacientes con EF. A diferencia de los pacientes con epilepsia temporal, en este grupo no existen estudios que exploren de manera cuantitativa cambios comunes en la estructura de la sustancia gris. Para ello se han empleado técnicas cuantitativa voxel por voxel que son altamente sensibles a cambios no identificables con inspección visual. La resonancia funcional (RMf) de lenguaje se ha integrado como parte importante de los estudios pre quirúrgicos en epilepsia. Esta necesidad se ve justificada por la alta incidencia de lateralización atípica del lenguaje en este grupo de pacientes. Este test se ha validado clínicamente en su mayoría utilizando la lengua nativa de los sujetos. Cuando el test se realiza en una segunda lengua como es el caso de población inmigrante se plantea la cuestión de la validez del test. Aunque existen un gran número de estudios de bilingüismo utilizando RMf, estos se han centrado en la búsqueda de diferencias en redes neuronales de las diferentes lenguas y no en el análisis de la validez clínica de estos mapas. En el tercer trabajo de la tesis se investiga las diferencias en los mapas de lenguajes obtenidos con RMf cuando se utiliza la lengua materna y cuando se utiliza una lengua secundaria. Con este estudio pretendemos evaluar la validez clínica de realizar mapeo de lenguaje con resonancia en una lengua secundaria.
Imaging techniques have led to the discovery of key questions in the field of epileptology. In this thesis, functional and structural aspects of focal epilepsies are investigated through magnetic resonance imaging (MRI). In particular, functional MRI and voxel wise analysis are used as the tool to test the hypothesis posed in the different studies that conform this thesis. The thesis is divided into three studies; two of them focus on frontal lobe epilepsy and the third one on language mapping of bilingual patients with epilepsy. Frontal lobe epilepsy is the second most prevalent syndrome among the focal epilepsies after temporal lobe epilepsy. However, it has proved challenging to characterize cognitive dysfunction within this group. Furthermore, the functional anatomy correlates of dysfunction in FLE is still unknown. Understanding these changes may help to characterize better the cognitive profile of this group. It may also improve the understanding of the changes in cognitive function as the result of surgery. In particular one of the studies focuses in memory function in patients with FLE. This cognitive aspect has received little attention in this group of patients. However, there is a significant prevalence of memory deficits in patients with Frontal lobe epilepsy. Using functional MRI (fMRI) I investigated long term memory in patients with FLE in order to characterize the functional anatomy that underlies memory dysfunction in this group of patients. The second study on FLE explores the structural changes in this syndrome. It uses voxel wise quantitative MRI techniques to identify common structural changes across this heterogeneous group. Language fMRI is widely used as part of the pre-surgical investigations of patients with drug resistant epilepsy. This is justified given the high prevalence of atypical language dominance in patients with epilepsy. The clinical validation of these tests have been performed using the subject’s native language. However this is a problem when the evaluated subject has to perform the test in a secondary language as it is the case of immigrant population. Although there is a large number of fMRI studies in bilingualism, these mainly focus in the differences in language networks between the different languages in bilinguals. The third study in this thesis investigates the differences in the language networks that support native and learned languages in bilingual patients with epilepsy and asses the clinical validity of mapping language using language paradigms in a subject’s first and second languages.

APA, Harvard, Vancouver, ISO, and other styles

17

Maynard, Lauren M. "Predictors of Epilepsy Severity in MRI-Identified Focal Cortical Dysplasia." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1458299543.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Soria, Pastor Sara. "Patterns of cerebral gray and white matter alterations in preterm subjects by magnetic resonance imaging." Doctoral thesis, Universitat de Barcelona, 2009. http://hdl.handle.net/10803/2294.

Full text

Abstract:

Preterm birth is frequently associated with an increased risk of neurodevelopmental difficulties and of cognitive, behavioural and emotional problems during childhood. The present thesis comprises two MRI studies that demonstrated patterns of cerebral gray matter (GM) and white matter (WM) alterations and their cognitive correlates in children and adolescents who were born preterm.
Our first study provided evidence of the persistence of diffuse WM abnormalities in adolescents who were born very preterm, and underlines their high frequency. The individual voxel-based morphometry analysis approach demonstrated that 80% of preterm subjects had WM abnormalities, the most frequently affected areas being the centrum semiovale and the posterior periventricular regions. These results suggest that WM reductions are common, even in those preterm subjects without motor impairment and who receive normal schooling. Volumetric and MRI-related cognitive outcomes suggest that cognitive processing speed is persistently impaired following early brain damage, despite the existence of developmental plasticity. Although the nature of the relationship between diffuse WM injury and cognitive/behavioural deficits is complex and not entirely understood, the results of our first study suggest that WM abnormalities are related with worse Performance IQ scores and slower processing speed. So, we can affirm that diffuse WM loss in preterm children plays an important role in long-term cognitive impairment.
Our second study focussed on the investigation of preterm children with a low risk either of neurological deficit or of developmental difficulties. While the neurodevelopmental and cognitive outcome of high-risk preterm samples is well known, little research has been conducted into low-risk preterms, such as those born between 30-34 weeks of GA, with uncomplicated perinatal histories, normal cranial ultrasound scans and no obvious neurodevelopmental deficits. To our knowledge, this is the first study to investigate the brain volume characteristics of a low-risk preterm sample in childhood using an MRI approach and the first attempt to relate these measures to cognitive performance. This study demonstrated that low-risk preterm children are characterized by the presence of regional cortical GM volume reductions in the parietal and temporal lobes which correlate strongly with IQ. Moreover, preterm children also showed WM volume reductions that were concomitant with the GM loss in the parietal and temporal regions compared to full-terms.
In summary, the body of results derived from this thesis provides evidence that preterm birth is associated with brain abnormalities and cognitive impairment in middle childhood and adolescence. Future studies are required to assess the impact of cognitive and behavioural function in middle childhood on later outcomes in preterm samples with low risk of neurodevelopmental deficits.
Les seqüeles cognitives i conductuals associades al naixement prematur constitueixen actualment un dels principals temes d'interès pediàtric. Les imatges per ressonància magnètica (RM) han resultat una eina interessant per a l'estudi de les lesions cerebrals associades a la prematuritat, encara que els correlats entre les troballes en RM i els indicatius del neurodesenvolupament estan poc investigats.
L'interès general d'aquesta tesi doctoral se centra en l'estudi de les bases neuroanatòmiques (patrons d'alteració de substància grisa i blanca cerebral) relacionades amb el rendiment cognitiu que presenten els nens i els adolescents que han nascut prematurs. Amb aquest objectiu s'han usat tècniques volumètriques de neuroimatge basades en imatges de RM, així com avaluacions cognitives i de conducta en dues mostres de nens i adolescents (edats mitges de 9 i 14 anys respectivament) amb antecedents de part prematur.
L'objectiu del primer estudi va ser investigar les relacions entre el rendiment cognitiu general i la integritat (concentració) de la substància blanca en una mostra d'adolescents que van néixer molt prematurs. Segons el nostre coneixement, cap estudi previ no havia usat la tècnica de la morfometria basada en el vòxel (VBM de l'anglès voxel-based morphometry) per analitzar els possibles correlats entre la substància blanca cerebral i els processos cognitius relacionats amb el quocient d'intel·ligència (QI) manipulatiu i amb mesures de velocitat de processament en una mostra d'adolescents amb antecedents de part prematur. A més a més, aquest va ser el primer estudi en usar una anàlisi de comparacions individuals amb la VBM a fi d'avaluar i establir els diferents patrons d'afectació de la substància blanca per a cada adolescent nascut prematur.
Mentre que el desenvolupament neurològic i cognitiu dels prematurs d'alt risc ha rebut molta atenció, pràcticament no hi ha estudis amb referència als prematurs amb baix risc a desenvolupar dèficits neurològics o cognitius. Els prematurs de baix risc es defineixen com aquells nascuts amb una prematuritat moderada (30-34 setmanes de gestació), sense evidències de complicacions neonatals associades, amb resultats d'ultrasons cranials normals i sense dèficits obvis del desenvolupament motor, cognitiu i social. Fins a la realització de la nostra segona investigació, cap altre estudi no havia investigat les característiques volumètriques d'una mostra de prematurs de baix risc mitjançant RM (tècnica VBM), ni havia relacionat aquestes mesures amb l'execució cognitiva.

Les conclusions d'aquesta tesi derivades de l'estudi I (I-III) i de l'estudi II (IV-VI) son:

I. Els adolescents amb antecedents de prematuritat, sense evidències d'alteracions en la substància blanca segons una inspecció visual neuroradiològica de les imatges de RM, presenten amb una freqüència elevada reduccions de concentració de substància blanca en comparació amb els adolescents nascuts a terme, usant la tècnica de neuroimatge voxel-based morphometry.

II. Els resultats dels anàlisis de patrons d'alteració de la substància blanca cerebral en prematurs adolescents mostren que el centre semioval i les regions periventriculars posteriors son les àrees més freqüentment afectades. Aquests resultats suggereixen que aquestes alteracions en substància blanca son altament comunes en subjectes amb antecedents de part prematur, i que persisteixen fins a l'adolescència, després d'un llarg període de maduració cerebral.

III. Els adolescents amb història de part prematur presenten una afectació major en el QI Manipulatiu que en el QI Verbal. Tanmateix, l'afectació difusa de la substància blanca cerebral té un efecte important en el rendiment cognitiu dels prematurs, sobretot en tasques d'organització perceptiva i de velocitat de processament.

IV. Els nens prematurs amb baix risc de desenvolupar dèficits del neurodesenvolupament presenten unes reduccions volumètriques de substància grisa cerebral tant globals com regionals localitzades principalment al lòbul temporal.

V. Els nens prematurs de baix risc presenten decrements de volum de la substància blanca adjacents a les regions d'afectació de la substància grisa, encara que a només a les regions temporals esquerres van assolir la significació estadística. Amb aquests resultats, queda palès que els nens prematurs de baix risc mostren una afectació principalment en la substància grisa cortical, amb reduccions associades, però no tant manifestes, de substància blanca. La integritat de les substàncies grisa i blanca cerebral en la infància estan relacionades amb variables neonatològiques tals com l'edat de gestació i el pes al néixer.

VI. El rendiment cognitiu dels nens prematurs de baix risc està caracteritzat per dèficits en la comprensió verbal i en el raonament perceptiu. Tanmateix, els nens prematurs de baix risc no mostren problemes de conducta o afectius en comparació amb els nens nascuts a terme.
Finalment, destacar que són necessaris estudis futurs que avaluïn els efectes de la prematuritat per se en el desenvolupament i la morfologia cerebral així com també en relació amb els subseqüents correlats cognitius.

APA, Harvard, Vancouver, ISO, and other styles

19

Burman, Joachim. "Curing Multiple Sclerosis : How to do it and how to prove it." Doctoral thesis, Uppsala universitet, Neurologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-221888.

Full text

Abstract:

Hematopoietic stem cell transplantation (HSCT) is a potentially curative treatment for multiple sclerosis (MS) with now more than 600 documented cases in the medical literature. Long-term remission can be achieved with this therapy, but when is it justified to claim that a patient is cured from MS? In attempt to answer this question, the outcome of the Swedish patients is described, mechanisms behind the therapeutic effect are discussed and new tools for demonstration of absence of disease have been developed. In Swedish patients treated with HSCT for aggressive MS, disease free survival was 68 % at five years, and no patient progressed after three years of stable disease. Presence of gadolinium enhancing lesions prior to HSCT was associated with a favorable outcome (disease free survival 79 % vs 46 %, p=0.028). There was no mortality and no patient required intensive care. The immune system of twelve of these patients was investigated further. In most respects HSCT-treated patients were similar to healthy controls, demonstrating normalization. In the presence of a potential antigen, leukocytes from HSCT-treated patients ceased producing pro-inflammatory IL-17 and increased production of the inhibitory cytokine TGF-β1 suggesting restoration of tolerance. Cytokine levels and biomarkers of tissue damage were investigated in cerebrospinal fluid from a cohort of MS patients. The levels were related to clinical and imaging findings. A cytokine signature of patients with relapsing-remitting MS could be identified, characterized by increased levels of CCL22, CXCL10, sCD40L, CXCL1 and CCL5 as well as down-regulation of CCL2. Further, we could demonstrate that active inflammation in relapsing-remitting MS is a tissue damaging process, with increased levels of myelin basic protein and neurofilament light. Importantly, relapsing-remitting MS patients in remission displayed no tissue damage. In secondary progressive MS, moderate tissue damage was present without signs of active inflammation. From a clinical vantage point, it seems that we confidently can claim cure of relapsing-remitting MS patients after five years absence of disease activity. The new tools for evaluation of disease can strengthen this assertion and may enable earlier prediction of outcome.

APA, Harvard, Vancouver, ISO, and other styles

20

Zhu, Jingyun, and 朱婧芸. "Volumetric and advanced functional MR imaging in neuropsychiatric systemic lupus erythematosus (NPSLE)." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47178966.

Full text

Abstract:

Neuropsychiatric systemic erythematosus (NPSLE) is a complicated complication of systemic erythematosus (SLE). Asian patients are associated with high prevalence of systemic disease and mortality It increases patients’ morbidity and mortality (Samanta et al., 1991). But the detailed pathology and pathogenesis are still remained unclear. Our study’s purpose is to use advanced functional imaging method, including diffusion tensor imaging (DTI) and magnetic resonance spectroscopy imaging (MRSI) to detect intracranial volumetry, functional and other metabolite changes in NPSLE patients. We recruited 3 age-matched female groups, one patient group with NPSLE (20 patients), one patient group with SLE (20 patients) and one control group (15 normal controls). Each patient was applied to structural 3D-T1 and axial T2, DTI and MRSI. Whole brain volumetry and hippocampus volumetry were analyzed by FSL and MARINA software from T1 images. White matter hyperintensity was calculated manually. Whole brain FA and other indices were collected. Regional FA was also collected and was collected with MRS over corpus callosum slice. The result showed no significant whole brain atrophy in NPSLE patients and SLE patients compared with controls. But with segmentation of grey matter, white matter and CSF, NPSLE patients showed significant decrease volume from SLE patients in white matter. Left hippocampus showed significant decreased volume in white matter and grey matter compared with control, while right hippocampus showed significant decreased volume in white matter. No other significant difference was found between NPSLE vs SLE and SLE vs controls. Whole brain FA was significantly decreased in NPSLE compared to SLE and controls, but not significantly different between SLE and controls. MD, λ∥ and λ⊥ were significantly increased in NPSLE and SLE compared with controls, but not significantly different between SLE and controls. White matter hyperintensity score was consistent with MD, λ∥ and λ⊥ results, showed significantly higher scores in two patients groups compared to controls. Regional FA, involving frontal lobes and corpus callosum, periventricular regions adjacent to centrum semiovale and posterior lateral temporal lobe, confirmed the regional FA decrease showed in whole brain FA statistical color map and NPSLE patients’ regional FA decrease correlated with MRS metabolic changes. N-acetyl aspartate (NAA)/ Creatine (Cr), the marker of neurons, decreased significantly in NPSLE patients compared with SLE and controls. Choline (Cho)/Cr showed significant increase of tendency of significant increase in NPSLE and SLE patients in some ROIs compared with controls. Our finding suggested that, although the whole brain atrophy is not obvious in NPSLE, the hippocampus and white matter suffered atrophy in NPSLE patients. These atrophy in white matter of whole brain and hippocampus combined with functional imaging results of DTI and MRS, indicated that NPSLE endured more severe axonal damage than SLE, which might be due to a variety of lesions, such as demyelination, microangiopathy, large vessel thrombosis, cytokine, etc. Varying ratio of NAA/Cr and Cho/Cr may be associated with the severity of axonal damage, probably due to demyelination in the background of inflammatory/ischemic/vasculitic changes.
published_or_final_version
Diagnostic Radiology
Master
Master of Philosophy

APA, Harvard, Vancouver, ISO, and other styles

21

Cerro, San Ildefonso Inés del. "Estudio clínico y de neuroimagen de la función noradrenérgica como indicador precoz de deterioro cognitivo." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/671473.

Full text

Abstract:

Los trastornos neurocognitivos (TNC) son un grupo heterogéneo de entidades clínicas cuya característica principal es el deterioro de todas o algunas de las capacidades funcionales y cognitivas previamente adquiridas por el individuo. Entre ellos encontramos el TNC mayor, tener múltiples etiologías, su causa más común es la enfermedad de Alzheimer (EA). Las marcas neuropatológicas distintivas de esta patología son la acumulación de placas de proteína β-amiloide y la de proteína tau hiperfosforilada que forma, entre otros, ovillos neurofibrilares. El primer lugar en el que se han detectado cambios en el proceso de formación de estas acumulaciones es el locus coeruleus (LC). Este es un núcleo situado en el tegmento pontino y es la mayor fuente de noradrenalina del sistema nervioso central. La integridad estructural del LC se ha investigado tanto en EA como en población en riesgo de desarrollar EA, sin embargo la preservación funcional de este núcleo a lo largo del continuum del TNC restaba sin estudiar. En esta tesis se presentan dos estudios centrados en la evaluación de la conectividad funcional entre el LC y diferentes regiones corticales y subcorticales, en grupos en riesgo de EA: hijos de pacientes con EA de inicio tardío (H-EAIT), individuos con deterioro cognitivo leve (DCL) y pacientes con trastorno depresivo mayor en edad avanzada (TDM); con el fin de comprobar si la medición de la funcionalidad del LC puede constituir un marcador precoz del comienzo del proceso neurodegenerativo en estas etapas tempranas del TNC. El primer estudio se centra en analizar la conectividad del LC en un grupo de H- EAIT, en comparación con sujetos sanos, durante una secuencia de resonancia magnética funcional en estado de reposo. En el segundo estudio se incluyó un grupo de DCL, de TDM y un grupo control; y se estudió la conectividad del LC durante la realización de una tarea oddball o de detección de estímulos, que permite estudiar la actividad neuronal del LC. En ambos casos correlacionamos los resultados de los análisis de neuroimagen con medidas clínicas, neuropsicológicas y conductuales, con el fin de caracterizar los patrones de alteración funcional y su asociación con posibles variables clínicas o cognitivas. Nuestros resultados apuntan a la disminución de la conectividad global del LC en el grupo de H-EAIT durante el estado de reposo y en TDM ante la detección de estímulos salientes (oddball). En ambos grupos observamos una disminución de la conectividad entre el LC y regiones del cerebelo posterior, implicadas en la modulación de la actividad de la red por defecto, de control ejecutivo y de saliencia. Igualmente, el grupo de TDM se caracteriza por presentar una disminución de la conectividad entre el LC y el giro fusiforme y la corteza cingulada anterior (CCA) ante los estímulos oddball. En los H-EAIT encontramos una correlación positiva entre la conectividad del LC-cerebelo posterior y medidas de recuerdo diferido que señala la implicación de este patrón en la función mnésica. Además, encontramos una asociación negativa entre la severidad de síntomas depresivos y la conectividad LC-cerebelo posterior. En los TDM, la conectividad LC-CCA se asocia negativamente con medidas de severidad y carga del trastorno depresivo, reflejo de la diferenciación entre dos subgrupos de pacientes depresivos: en episodio activo de depresión y en remisión. Los resultados de este estudio confirman que existen alteraciones en la conectividad del LC en estadios iniciales del TNC y en población con un riesgo incrementado de desarrollo de EA. Además, apoyan la modulación del LC de regiones corticales y subcorticales implicadas en función mnésica, atencional y regulación del arousal. Esta tesis supone un punto de base para la investigación más profunda del LC a lo largo del continuo del TNC, con el fin de poder desarrollar herramientas diagnósticas no invasivas que permitan detectar precozmente procesos neurodegenerativos y el desarrollo de tratamientos más personalizados.
Neurocognitive disorders (NCD) are a heterogeneous group of clinical entities that share as a principal hallmark the impairment in all or some of the previously acquired cognitive and functional capacities. Among this group, Alzheimer’s disease (AD) is the most prevalent cause of NCD. The two biological hallmarks of AD are the β-amyloid plaques and hyperphosphorylated tau neurofibrillary tangles. The locus coeruleus (LC) nucleus, the major source of noradrenaline to the central nervous system, is the region where pathological changes start in the continuum of AD. Structural integrity of this nucleus has been investigated in AD and AD at-risk population, but its functional preservation remained unstudied. In this thesis, we present two studies focused in the LC functional connectivity. The first study included a group of offspring of late onset AD (O-LOAD) and we used a resting-state functional magnetic resonance (rs-fMRI). For the second study a group of mild cognitive impairment (MCI) and late-life major depressive disorder (MDD) were recruited and they performed an oddball task during the acquisition of functional magnetic resonance imaging (fMRI). In both works, neuroimaging results were correlated with clinical, neuropsychological and behavioral data. Firstly, we found that both O-LOAD and MDD groups showed a diminished LC global connectivity, and these groups also presented a lower connectivity between LC and posterior cerebellum regions, during rs-fMRI and the oddball task, respectively. Moreover, MDD showed a lower connectivity between LC and fusiform gyrus and anterior cingulate cortex (ACC) in front of oddball stimuli. In O-LOAD we observed a negative association between LC-posterior cerebellum and depression symptoms and memory measures; and MDD showed an inverse correlation between LC-CCA connectivity and depression severity and the number of episodes measures. Our results point to the presence of connectivity alterations of LC in early stages of NCD and in AD at- risk population. A deeper investigation of functional activity and connectivity of the LC through the NCD continuum would be useful for the development of non-invasive diagnostic tools and the development of personalized treatments.

APA, Harvard, Vancouver, ISO, and other styles

22

Valverde, Valverde Sergi. "Automated brain tissue segmentation of magnetic resonance images in multiple sclerosis." Doctoral thesis, Universitat de Girona, 2016. http://hdl.handle.net/10803/386468.

Full text

Abstract:

L'objectiu principal d'aquesta tesi és el desenvolupament d'un nou mètode de segmentació totalment automàtic capaç de mesurar amb precisió el volum cerebral en imatges de pacients d'EM amb lesions. El mètode que hem proposat s'ha desenvolupat i implementat integrant no només la informació provinent de la intensitat dels vòxels, sinó a través de la incorporació d'atles morfològics i estructurals que guien la segmentació del teixit. Els vòxels candidats de ser lesions són estimats i processats abans de la segmentació del teixit utilitzant un algoritme de post-processat basat en la informació del context local i la informació anatòmica i morfològica prèvia. Aquest mètode de segmentació ha estat avaluat de forma quantitativa i qualitativa utilitzant diferents conjunts d'imatges que contenen lesions de substància blanca. Els resultats mostren que la precisió del mètode proposat és consistent i molt competitiva en tot tipus d'imatges en comparació amb altres tècniques proposades. En aquest sentit, els percentatges d'error obtinguts en els diferents experiments duts a terme mostren que el mètode proposat millora la segmentació del teixit cerebral de les imatges amb lesions
The main goal of this thesis is to develop a novel, fully automated brain tissue segmentation method capable of computing accurate measurements of tissue volume from images of MS patients with lesions. The proposed tissue segmentation method has been designed and implemented using a combination of intensity along with anatomical and morphological prior maps to guide the tissue segmentation. WM outliers have been estimated and filled with signal intensities similar to those of the WM before segmentation using a multi-channel post-processing rule-based algorithm with spatial context, and prior anatomical and morphological atlases. The proposed method has been quantitatively and qualitatively evaluated using different databases of images containing WM lesions, yielding competitive and consistent results in both general and MS specific databases. The percentages of errors obtained in the different experiments carried out show that the proposed algorithm effectively improves automated brain tissue segmentation in images containing lesions.

APA, Harvard, Vancouver, ISO, and other styles

23

Arrambide, García Georgina. "Study of diagnostic and prognostic clinical, biological, and magnetic resonance imaging markers at the time of a clinically isolated syndrome." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/384610.

Full text

Abstract:

En este trabajo estudiamos marcadores con valor diagnóstico o pronóstico en el momento de presentar un síndrome clínico aislado (CIS, del inglés clinically isolated syndrome). Dado que presentar un CIS representa un riesgo para desarrollar esclerosis múltiple (EM), se considera crucial identificar qué pacientes tendrán un segundo brote y determinar el grado de acumulación de discapacidad a medio y largo plazo. Por ello, aún se considera necesario identificar marcadores que representen los diferentes aspectos de esta enfermedad, especialmente si se demuestra su utilidad en la práctica clínica diaria. Así, nuestro objetivo fue determinar el valor diagnóstico y pronóstico de marcadores clínicos, biológicos y radiológicos en el momento del CIS. Primero, dado que el espectro de enfermedades de la neuromielitis óptica (NMOSD, del inglés neuromyelitis optica spectrum disorders) es uno de los principales diagnósticos diferenciales de la EM, decidimos evaluar la utilidad de determinar sistemáticamente la presencia de anticuerpos NMO-IgG en el momento del CIS, observando que tal abordaje no es necesario ya que la determinación de este anticuerpo fue negativa en la mayoría de los pacientes. Por tanto, otras características clínicas y radiológicas también deben considerarse durante el diagnóstico diferencial y esta determinación podría realizarse en casos indeterminados. Posteriormente se estableció una colaboración con Aurélie Ruet y Bruno Brochet [Centre Hospitalo-Universitaire (CHU) de Bordeaux, INSERM-CHU centre d’Investigation Clinique, Université de Bordeaux en Francia] para evaluar más a fondo el valor añadido de presentar dos o más factores predictivos de EM, previamente identificados por ellos, en pacientes con CIS que no cumplen los criterios diagnósticos de 2010 para diseminación en espacio, observando que si bien es más bajo, los pacientes con combinaciones de estos factores aún presentan un riesgo de desarrollar EM y deberían ser monitorizados más estrechamente. De igual forma, la utilidad de realizar una RM medular en el momento del CIS se considera un tema controvertido. Por tanto, analizamos su valor diagnóstico y pronóstico añadido, observando que aunque su aportación a los criterios diagnósticos es más bien modesta, la presencia de lesiones medulares representa un riesgo aumentado para evolucionar a una EM y para desarrollar una mayor discapacidad. También establecimos otra colaboración con la compañía israelí Glycominds, Inc., para validar el valor predictivo del gMS-Classifier2, un algoritmo que incorpora anticuerpos anti-glicano IgM en suero, diseñado con el objetivo de identificar pacientes con CIS en riesgo de presentar un segundo brote. El gMS-Classifier2 resultó ser un factor de riesgo independiente para EM, si bien los hallazgos en la RM representan un riesgo más elevado. Finalmente, valoramos varios marcadores biológicos en líquido cefalorraquídeo durante una fase de screening y una de validación que requirió trabajos colaborativos con Jens Kuhle, Ludwig Kappos (Department of Neurology, University Hospital Basel, en Suiza), Luisa María Villar y José Carlos Álvarez-Cermeño [Departamentos de Inmunología y Neurología del Hospital Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS) en Madrid]. De todos los biomarcadores testados, los niveles basales de NfL resultaron ser factores independientes de riesgo para desarrollar una EM, siendo los hallazgos de RM nuevamente los mayores indicadores de riesgo. Además, los NfL presentaron fuertes correlaciones con los cambios en el volumen cerebral a los cinco años de seguimiento.
The present work is concerned with finding diagnostic and prognostic markers at the time of a clinically isolated syndrome (CIS). Given that presenting a CIS indicates the possibility of developing multiple sclerosis (MS), it is considered crucial to identify which patients will present a second attack and to determine the degree of disability accumulation over the medium to long-term. Therefore, the search for markers that capture the different aspects of this disease is still considered necessary, particularly if they demonstrate to be useful in the daily clinical practice. Therefore, we aimed to determine the diagnostic and prognostic value of a number of clinical, biological, and radiological markers available at the time of the CIS. First, considering neuromyelitis optica spectrum disorders (NMOSD) as one of the main differential diagnoses of MS after a first attack, we decided to assess the value of systematically determining NMO-IgG status at the time of a CIS, observing that such approach is not necessary since the antibody determination was negative in most patients. Therefore, other clinical and radiological characteristics should also be taken into account during the differential diagnosis and this test could be considered in indeterminate cases. Next, a collaborative work was established with Drs. Aurélie Ruet and Bruno Brochet [Centre Hospitalo-Universitaire (CHU) de Bordeaux, INSERM-CHU centre d’Investigation Clinique, Université de Bordeaux, France] to further assess the added value of presenting ≥2 predictive factors for MS, previously identified by them, in patients not fulfilling the 2010 criteria for dissemination in space, and observed that although lower, patients with combinations of these predictive factors are still at risk of developing MS and should be monitored closely. Likewise, the usefulness of a baseline spinal cord MRI at the time of a CIS is still somewhat controversial. Therefore, we analysed its added diagnostic and prognostic value, observing that although the diagnostic value is modest, presence of spinal cord lesions do pose an increased and independent risk for both evolution to MS and disability accumulation. One more collaboration was established with the Israeli company Glycominds, Inc., to validate the predictive value of gMS-Classifier2, an algorithm incorporating serum IgM anti-glycan antibodies, designed with the aim of identifying CIS patients at risk of a second demyelinating attack. gMS-Classifier2 turned out to be an independent risk factor for clinically definite MS, although MRI findings still posed a higher risk. Finally, we evaluated a number of biological markers in cerebrospinal fluid during a screening and a validation phase that involved a couple of collaborative works with Jens Kuhle, Ludwig Kappos (Department of Neurology, University Hospital Basel, in Switzerland), Luisa María Villar, and José Carlos Álvarez-Cermeño (Departments of Neurology and Immunology, Multiple Sclerosis Unit, Hospital Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS) in Madrid). Of all biomarkers, only baseline neurofilament light chain levels were independent risk factors for MS with MRI findings again posing the highest risk but, interestingly, they showed very strong correlations with brain volume changes at five years of follow-up.

APA, Harvard, Vancouver, ISO, and other styles

24

Simoni, Michela. "Age-related white matter changes in patients with TIA and stroke : population-based study on aetiological and prognostic significance." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:d3e55744-5cc1-44e9-a33f-589abbc50c93.

Full text

Abstract:

White matter changes (WMC) seen on CT and MRI brain scans of healthy subjects and of vascular or dementia patients are strongly associated with age. Their pathogenesis is still under debate, and associations with vascular risk factors have varied according to studies. Their prognostic meaning, both in the general population and in stroke patients, is also not completely established. I systematically reviewed the literature on prevalence and associations of WMC and then evaluated CT and MRI scans of the first 8 years of a population-based study of all strokes and TIA in Oxfordshire (OXVASC). In this population I researched sex and age-specific associations between WMC and different types of strokes (TOAST), different components of blood pressure, and possible vascular risk factors. I also looked into their prognostic meaning for stroke recurrence and outcome, cognitive performance and mortality. 1840 patients were assessed by MRI (520) and/or CT (1717). White matter changes were independently associated with the lacunar type of stroke. The association with hypertension was confirmed (using 10 years of pre-morbid blood pressure readings), and it was particularly strong in the younger patients, mainly for diastolic hypertension. There was no association with blood pressure variability and peripheral pulse pressure. Hypercholesterolaemia, diabetes, smoking, ischaemic heart disease, carotid stenosis and atrial fibrillation were not associated with white matter changes. There was also no association with gender. Severe WMC posed a higher risk of disability and cognitive impairment at one year from the stroke, and of death in the following 10 years. This is the first study on white matter changes associations and on their prognostic meaning, to be set in a large population-based cohort of stroke and TIA. I confirmed the association between white matter changes and higher blood pressure, in particular diastolic hypertension. I also showed the association with lacunar type of stroke to be independent from vascular risk factors, and WMC to reduce life expectancy and functional and cognitive outcome of patients with stroke.

APA, Harvard, Vancouver, ISO, and other styles

25

Flanagan, Shawn D. "Neurological Basis of Persistent Functional Deficits after Traumatic Musculoskeletal Injury." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469031876.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Kaukola, T. (Tuula). "Perinatal brain damage in very preterm infants:prenatal inflammation and neurologic outcome in children born term and preterm." Doctoral thesis, University of Oulu, 2005. http://urn.fi/urn:isbn:9514278402.

Full text

Abstract:

Abstract Despite improvements in peri- and neonatal care and an increase in the overall survival of very preterm infants, the incidence of neurologic sequelae has remained high. The pathogenesis of many brain imaging findings, such as white matter damage, WMD, is poorly understood. The factors predisposing to brain damage differ between term and preterm infants. More detailed information is needed of how brain imaging correlates with neurodevelopmental impairment after the neonatal period. The present study investigated the pre- and perinatal factors leading to brain damage and their effects on neurologic and neurodevelopmental outcome in very preterm children. We also analyzed the differences in umbilical cord serum cytokines in term and preterm children with cerebral palsy, CP. Furthermore, the correlations between the findings on diffusion-weighted imaging, DWI, measurements in brainstem auditory evoked potentials, and neurodevelopmental outcome were assessed. We demonstrated that pregnancies complicated by combined histologic chorioamnionitis and placental insufficiency independently predicted abnormal neurologic outcome at 2 years of corrected age. WMD additively predicted poor outcome. Isolated fetal inflammatory response, umbilical cord serum acute phase cytokines (IL-1α, IL-1β, IL-6, IL-8, TNF-α), did not associate with neurologic outcome in either term or preterm children. Instead, a cluster of cytokines different from acute phase cytokines were related to CP, and the protein profile differed between term and preterm children. Disturbed hemodynamics during the pre- and perinatal period affected outcome in very preterm infants. In severe placental insufficiency, fetal cardiac compromise associated with suboptimal neurodevelopmental outcome at 1 year of corrected age. In addition, several clinical factors characterising cardiorespiratory status after birth associated with abnormal neurologic outcome at 2 years of corrected age. We found the apparent diffusion coefficient, ADC, a quantitative measurement of water diffusion, in pons to correlate with the conduction rate of impulses travelling through the auditory tract. We also demonstrated a high value of ADC in corona radiata to associate with poor outcome in gross motor and eye-hand coordination skills at 2 years of corrected age. Both pre- and perinatal factors associate with later outcome in very preterm infants. An isolated fetal inflammatory response does not predict neurologic outcome. Findings on DWI in specific brain regions predict abnormal neurodevelopmental outcome
Tiivistelmä Huolimatta vastasyntyneisyyskauden parantuneista hoitotuloksista ja että yhä useampi hyvin ennenaikaisena syntynyt lapsi jää eloon, heidän neurologisen vammautuneisuuden ilmaantuvuus on edelleen korkea. Monien aivojen kuvantamislöydösten, kuten valkean aineen vaurion, syntymekanismit tunnetaan huonosti. Aivojen vaurioitumiselle altistavat tekijät eroavat täysiaikaisena ja ennenaikaisena syntyneillä lapsilla. Tarvitaan myös aiempaa yksityiskohtaisempaa tietoa aivojen kuvantamislöydösten merkityksestä lasten vastasyntyneisyyskauden jälkeiseen kehitykseen. Tässä tutkimuksessa selvitettiin raskauden- ja syntymänaikaisia tekijöitä, jotka vaikuttavat aivojen vaurioitumiseen hyvin ennenaikaisena syntyneillä lapsilla sekä näiden tekijöiden merkitystä lasten neurologiseen kehitykseen. Tarkastelimme myös napaveren seerumin välittäjäaineiden, sytokiinien, eroavuuksia täysiaikaisena ja ennenaikaisena syntyneillä CP-lapsilla. Lisäksi selvitimme diffuusiomagneettitutkimus- ja aivorunkoherätevastelöydösten sekä neurologisen kehityksen välisiä yhteyksiä. Tämän tutkimuksen mukaan kohdunsisäinen tulehdus ja istukan vajaatoiminta yhtä aikaa esiintyessään ovat poikkeavan neurologisen kehityksen itsenäisiä riskitekijöitä lapsilla 2 vuoden korjatussa iässä tutkittuna. Valkoisen aivoaineen vaurio edelleen lisäsi näiden lasten huonon neurologisen kehityksen ennustetta. Raskauden kestosta riippumatta, sikiön tulehdusvastetta kuvaavat napaveren akuutin vaiheen tulehdusvälittäjäaineet (IL-1α, IL-1β, IL-6, IL-8, TNF- α) eivät vaikuttaneet lapsen neurologiseen kehitykseen. Sen sijaan, CP-lasten napaverestä löytyi erityinen joukko ei-akuutin vaiheen välittäjäaineita. Nämä valkuaisaineet erosivat toisistaan täysiaikaisena ja ennenaikaisena syntyneillä CP-lapsilla. Raskauden- ja syntymänaikaiset verenkierron häiriöt vaikuttivat hyvin ennenaikaisena syntyneiden lasten myöhempään kehitykseen. Vaikeassa istukan vajaatoiminassa sikiön sydämen toiminnan heikkeneminen liittyi lapsen suboptimaaliin neurologiseen kehitykseen 1 vuoden korjatussa iässä tutkittuna. Lisäksi useat syntymänjälkeiset keuhkojen ja verenkierron tilaa kuvaavat kliiniset tekijät liittyivät lapsen poikkeavaan neurologiseen kehitykseen 2 vuoden korjatussa iässä tutkittuna. Tutkimuksemme mukaan, veden diffuusiota määrällisesti kuvaava diffuusiokerroin, ADC, aivosillasta mitattuna, liittyi impulssien johtumisnopeutueen kuuloradastossa. Lisäksi korkea ADC-arvo aivojen sepelviuhkassa liittyi karkean motoriikan ja silmä-käsi-yhteistyötaitojen huonoon kehitykseen 2 vuoden korjatussa iässä tutkittuna. Sekä raskauden- että syntymänaikaiset tekijät vaikuttavat hyvin ennenaikaisena syntyneiden lasten myöhempään kehitykseen. Yksittäinen sikiön tulehdusvaste ei ennakoi lapsen neurologista kehitystä. Tiettyjen aivoalueiden diffuusiokuvantamislöydökset ennustavat lapsen poikkeavaa neurologista kehitystä

APA, Harvard, Vancouver, ISO, and other styles

27

Lee, Kuan Jin. "Fast magnetic resonance imaging." Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397487.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

O'Neil, Shannon M. "Magnetic resonance imaging centers /." Online version of thesis, 1994. http://hdl.handle.net/1850/11916.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Lu, Wenmiao. "Off-resonance correction in magnetic resonance imaging /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Manners, David Neil. "Magnetic resonance imaging and magnetic resonance spectroscopy of skeletal muscle." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269250.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Petropoulos, Labros Spiridon. "Magnetic field issues in magnetic resonance imaging." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1060710667.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Campbell, Jennifer 1975. "Magnetic resonance diffusion tensor imaging." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30809.

Full text

Abstract:

Magnetic resonance imaging (MRI) can be used to image diffusion in liquids, such as water in brain structures. Molecular diffusion can be isotropic or anisotropic, depending on the fluid's environment, and can therefore be characterized by a scalar, D, or by a tensor, D, in the respective cases. For anisotropic environments, the eigenvector of D corresponding to the largest eigenvalue indicates the preferred direction of diffusion.
This thesis describes the design and implementation of diffusion tensor imaging on a clinical MRI system. An acquisition sequence was designed and post-processing software developed to create diffusion trace images, scalar anisotropy maps, and anisotropy vector maps. A number of practical imaging problems were addressed and solved, including optimization of sequence parameters, accounting for flow effects, and dealing with eddy currents, patient motion, and ghosting. Experimental validation of the sequence was performed by calculating the trace of the diffusion tensor measured in various isotropic liquids. The results agreed very well with the quantitative values found in the literature, and the scalar anisotropy index was also found to be correct in isotropic phantoms. Anisotropy maps, showing the preferred direction of diffusion, were generated in human brain in vivo. These showed the expected white matter tracts in the corpus callosum.

APA, Harvard, Vancouver, ISO, and other styles

33

Eichner, Cornelius. "Slice-Accelerated Magnetic Resonance Imaging." Doctoral thesis, Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184944.

Full text

Abstract:

This dissertation describes the development and implementation of advanced slice-accelerated (SMS) MRI methods for imaging blood perfusion and water diffusion in the human brain. Since its introduction in 1977, Echo-Planar Imaging (EPI) paved the way toward a detailed assessment of the structural and functional properties of the human brain. Currently, EPI is one of the most important MRI techniques for neuroscientific studies and clinical applications. Despite its high prevalence in modern medical imaging, EPI still suffers from sub-optimal time efficiency - especially when high isotropic resolutions are required to adequately resolve sophisticated structures as the human brain. The utilization of novel slice-acceleration methods can help to overcome issues related to low temporal efficiency of EPI acquisitions. The aim of the four studies outlining this thesis is to overcome current limitations of EPI by developing methods for slice-accelerated MRI. The first experimental work of this thesis describes the development of a slice-accelerated MRI sequence for dynamic susceptibility contrast imaging. This method for assessing blood perfusion is commonly employed for brain tumor classifications in clinical practice. Following up, the second project of this thesis aims to extend SMS imaging to diffusion MRI at 7 Tesla. Here, a specialized acquisition method was developed employing various methods to overcome problems related to increased energy deposition and strong image distortion. The increased energy depositions for slice-accelerated diffusion MRI are due to specific radiofrequency (RF) excitation pulses. High energy depositions can limit the acquisition speed of SMS imaging, if high slice-acceleration factors are employed. Therefore, the third project of this thesis aimed at developing a specialized RF pulse to reduce the amount of energy deposition. The increased temporal efficiency of SMS imaging can be employed to acquire higher amounts of imaging data for signal averaging and more stable model fits. This is especially true for diffusion MRI measurements, which suffer from intrinsically low signal-to-noise ratios. However, the typically acquired magnitude MRI data introduce a noise bias in diffusion images with low signal-to-noise ratio. Therefore, the last project of this thesis aimed to resolve the pressing issue of noise bias in diffusion MRI. This was achieved by transforming the diffusion magnitude data into a real-valued data representation without noise bias. In combination, the developed methods enable rapid MRI measurements with high temporal efficiency. The diminished noise bias widens the scope of applications of slice- accelerated MRI with high temporal efficiency by enabling true signal averaging and unbiased model fits. Slice-accelerated imaging for the assessment of water diffusion and blood perfusion represents a major step in the field of neuroimaging. It demonstrates that cur- rent limitations regarding temporal efficiency of EPI can be overcome by utilizing modern data acquisition and reconstruction strategies.

APA, Harvard, Vancouver, ISO, and other styles

34

Lindsay, Alistair. "Magnetic resonance imaging of atherosclerosis." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526491.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Glover, Paul Martin. "High field magnetic resonance imaging." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335575.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Yoo, Seung-Schik 1970. "Adaptive functional magnetic resonance imaging." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/70893.

Full text

Abstract:

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2000.
Some research performed with the Harvard-M.I.T. Division of Health Sciences and Technology.
Includes bibliographical references (leaves 132-140).
Functional MRI (fMRI) detects the signal associated with neuronal activation, and has been widely used to map brain functions. Locations of neuronal activation are localized and distributed throughout the brain, however, conventional encoding methods based on k-space acquisition have limited spatial selectivity. To improve it, we propose an adaptive fMRI method using non-Fourier, spatially selective RF encoding. This method follows a strategy of zooming into the locations of activation by progressively eliminating the regions that do not show any apparent activation. In this thesis, the conceptual design and implementation of adaptive fMRI are pursued under the hypothesis that the method may provide a more efficient means to localize functional activities with increased spatial or temporal resolution. The difference between functional detection and mapping is defined, and the multi- resolution approach for functional detection is examined using theoretical models simulating variations in both in-plane and through-plane resolution. We justify the multi-resolution approach experimentally using BOLD CNR as a quantitative measure and compare results to those obtained using theoretical models. We conclude that there is an optimal spatial resolution to obtain maximum detection; when the resolution matches the size of the functional activation. We demonstrated on a conventional 1.5-Tesla system that RF encoding provides a simple means for monitoring irregularly distributed slices throughout the brain without encoding the whole volume. We also show the potential for increased signal-to-noise ratio with Hadamard encoding as well as reduction of the in-flow effect with unique design of excitation pulses.
(cont.) RF encoding was further applied in the implementation of real-time adaptive fMRI method, where we can zoom into the user-defined regions interactively. In order to do so, real-time pulse prescription and data processing capabilities were combined with RF encoding. Our specific implementation consisted of five scan stages tailored to identify the volume of interest, and to increase temporal resolution (from 7.2 to 3.2 seconds) and spatial resolution (from 10 mm to 2.5-mm slice thickness). We successfully demonstrated the principle of the multi- resolution adaptive fMRI method in volunteers performing simple sensorimotor paradigms for simultaneous activation of primary motor as well as cerebellar areas.
by Seung-Schik Yoo.
Ph.D.

APA, Harvard, Vancouver, ISO, and other styles

37

Harvey, Ian. "Magnetic resonance imaging in schizophrenia." Thesis, University of Edinburgh, 1991. http://hdl.handle.net/1842/19829.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Yoshimaru, Eriko Suzanne. "Magnetic Resonance Imaging Techniques for Rodent Pulmonary Imaging." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/293388.

Full text

Abstract:

Magnetic Resonance Imaging (MRI) is a safe and widely used diagnostic imaging method that allows in vivo observation of anatomy and characterization of tissues. MRI provides a method to monitor patients without invasive measures, making it suitable for both diagnostics and longitudinal monitoring of various pathologies. A notable example of this is the work carried out by the Alzheimer's Disease Neuroimaging Initiative (ADNI), which utilizes imaging, including multiple MRI techniques, to monitor disease progression in AD patients and evaluates treatment responses and prevention strategies. Similarly, MRI has been extensively used in evaluating diseases in a variety of animal models. In order to detect subtle anatomical changes over time, small differences in MR images must be accurately extracted. Furthermore, to ensure that the extracted differences are due to anatomical changes rather than equipment variance, it becomes essential to monitor and to assess the MRI system stability. In the first chapter of the dissertation, a method for monitoring pre-clinical MRI system performance is discussed. The technique developed during the study provides a fast and simple method to monitor pre-clinical MRI systems but also has applications for all areas of MRI. The second chapter describes the development of a 3D UTE MRI method for pulmonary imaging in freely breathing mice. The development of the 3D UTE sequence for pulmonary MRI has demonstrated its ability to collect images without noticeable motion artifacts and with appreciable signal from the lung parenchyma. Furthermore, images at two distinct respiratory phases were reconstructed from a single data set, providing functional information of the rodents' lungs. Finally, in the third chapter, 3D ¹⁹F UTE MRI is evaluated for imaging in vivo distributions of perfluorocarbon (PFC) nanoemulsions for measuring pulmonary inflammation. Building upon the development of pulmonary imaging, fluorinated contrast agents made from PFCs were used to target immune cells in response to pulmonary pathology. Both 3D ¹H and ¹⁹F UTE MRI were used to acquire pulmonary images of mouse models documented to have pulmonary pathology. Even though the mice had confirmed elevation in alveolar macrophage counts, no visible ¹⁹F signal accumulation within the pulmonary tissue was observed with MRI.

APA, Harvard, Vancouver, ISO, and other styles

39

Sharkey-Toppen, Travis P. "Imaging Iron and Atherosclerosis by Magnetic Resonance Imaging." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429796182.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

MA, DAN. "Magnetic Resonance Fingerprinting." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1426170542.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Lei, Hao. "Magnetic resonance perfusion imaging and double quantum coherence transfer magnetic resonance spectroscopy." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0021/NQ45007.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

McDougall, Mary Preston. "Single echo acquisition magnetic resonance imaging." Texas A&M University, 2004. http://hdl.handle.net/1969.1/3324.

Full text

Abstract:

The dramatic improvement in magnetic resonance imaging (MRI) scan time over the past fifteen years through gradient-based methods that sample k-space more efficiently and quickly cannot be sustained, as thresholds regarding hardware and safety limitations are already being approached. Parallel imaging methods (using multiple receiver coils to partially encode k-space) have offered some relief in the efforts and are rapidly becoming the focus of current endeavors to decrease scan time. Ideally, for some applications, phase encoding would be eliminated completely, replaced with array coil encoding instead, and the entire image formed in a single echo. The primary objective of this work was to explore that acceleration limit Â to implement and investigate the methodology of single echo acquisition magnetic resonance imaging (SEA MRI). The initial evaluation of promising array coil designs is described, based on parameters determined by the ability to enable the imaging method. The analyses of field patterns, decoupling, and signal-to-noise ratio (SNR) that led to the final 64-channel array coil design are presented, and the fabrication and testing of coils designed for 4.7T and 1.5T are described. A detailed description of the obtainment of the first SEA images Â 64xNreadout images, acquired in a single echo Â is provided with an evaluation of those images and highly accelerated images (through parallel imaging techniques) based on SNR and artifact power. Finally, the development of methodologies for various MR applications is described: applications that would particularly benefit from the speed of the imaging method, or those to which the method or the tool (array coil) lends itself. These applications include, but are not limited to, 3D imaging (phase encode in the slice select direction), resolution-enhanced imaging, large-scale (field-of-view) microscopy, and conformal surface imaging. Finally, using the primary enablement of the method Â the ability to obtain complete MR images at speeds limited only by the time it takes to acquire a single echo Â is presented with a discussion of extremely high frame rate imaging. The contribution to the field of medical imaging is the first implementation, characterization, and demonstration of applications for the acquisition of MR images in a single echo.

APA, Harvard, Vancouver, ISO, and other styles

43

Brown, David Gerald. "Instrumentation for parallel magnetic resonance imaging." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4784.

Full text

Abstract:

Parallel magnetic resonance (MR) imaging may be used to increase either the throughput or the speed of the MR imaging experiment. As such, parallel imaging may be accomplished either through a "parallelization" of the MR experiment, or by the use of arrays of sensors. In parallelization, multiple MR scanners (or multiple sensors) are used to collect images from different samples simultaneously. This allows for an increase in the throughput, not the inherent speed, of the MR experiment. Parallel imaging with arrays of sensor coils, on the other hand, makes use of the spatial localization properties of the sensors in an imaging array to allow a reduction in the number of phase encodes required in acquiring an image. This reduced phase-encoding requirement permits an increase in the overall imaging speed by a factor up to the number of sensors in the imaging array. The focus of this dissertation has been the development of cost-effective instrumentation that would enable advances in the state of the art of parallel MR imaging. First, a low-cost desktop MR scanner was developed (< $13,000) for imaging small samples (2.54 cm fields-of view) at low magnetic field strengths (< 0.25 T). The performance of the prototype was verified through bench-top measurements and phantom imaging. The prototype transceiver has demonstrated an SNR (signal-to-noise ratio) comparable to that of a commercial MR system. This scanner could make parallelization of the MR experiment a practical reality, at least in the areas of small animal research and education. A 64-channel receiver for parallel MR imaging with arrays of sensors was also developed. The receiver prototype was characterized through both bench-top tests and phantom imaging. The parallel receiver is capable of simultaneous reception of up to sixty-four, 1 MHz bandwidth MR signals, at imaging frequencies from 63 to 200 MHz, with an SNR performance (on each channel) comparable to that of a single-channel commercial MR receiver. The prototype should enable investigation into the speed increases obtainable from imaging with large arrays of sensors and has already been used to develop a new parallel imaging technique known as single echo acquisition (SEA) imaging.

APA, Harvard, Vancouver, ISO, and other styles

44

Tymofiyeva, Olga. "Magnetic resonance imaging in dental medicine." Göttingen Sierke, 2010. http://d-nb.info/1002094976/04.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Kristoffersen, Wiberg Maria. "Magnetic resonance imaging in breast diagnosis /." Stockholm : Karolinska Univ. Press, 2002. http://diss.kib.ki.se/2002/91-7349-343-0.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Blomqvist, Lennart. "Magnetic resonance imaging of rectal tumours /." Stockholm, 1997. http://diss.kib.ki.se/1997/91-628-2797-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Graff, Christian George. "Parameter Estimation in Magnetic Resonance Imaging." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/195912.

Full text

Abstract:

This work concerns practical quantitative magnetic resonance (MR) imaging techniques and their implementation and use in clinical MR systems. First, background information on MR imaging is given, including the physics of the magnetic resonance, relaxation effects and how imaging is accomplished.Subsequently, the first part of this work describes the estimation of the T2 relaxation parameter from fast spin-echo (FSE) data. Various complications are considered, including partial volume and data from multiple receiver coils along with the effects of the timing parameters on the accuracy of T2 estimates. Next, the problem of classifying small (1 cm diameter) liver lesions using T2 estimates obtained from radially-acquired FSE data collected in a single breath-hold is considered. Several algorithms are proposed for obtaining lesion T2 estimates, and these algorithms are evaluated with a task-based metric, their ability to separate two classes of lesions, benign and malignant. A novel computer-generated phantom is developed for the generation of the data used in this evaluation.The second part of this work describes techniques that perform the separation of water and lipid signals while simultaneously estimating relaxation parameters that have clinical relevance. The acquisition sequences used here are Cartesian and radial versions of Gradient and Spin-Echo (GRASE). The radial GRASE technique is post-processed with a novel algorithm that estimates the T2 of the water signal independent of the lipid signal. The accuracy of this algorithm is evaluated in phantom and its potential use for detecting inflammation of the liver is evaluated using clinical data. Cartesian GRASE data is processed to obtain T2-dagger and lipid fraction estimates in bone which can be used to assess bone quality. The algorithm is tested in phantom and in vivo, and preliminary results are given.In the concluding chapter results are summarized and directions for future work are indicated.

APA, Harvard, Vancouver, ISO, and other styles

48

Li, Zhiqiang. "Novel Body Magnetic Resonance Imaging Techniques." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/193829.

Full text

Abstract:

Body magnetic resonance imaging (MRI) has progressed rapidly over the last 12 years. The advances in hardware and software have allowed the implementation of faster and better pulse sequences for body imaging. Despite the improvements in MRI technology there are still problems associated with current body MRI techniques that limit their diagnostic capabilities. The main goal of this work is to develop novel body MRI methods to improve the diagnosis of cardiac and abdominal pathologies. One of the goals of this work is to develop a technique to improve the detection of lipid infiltration in the heart. For this purpose an interleaved double-inversion fast spin-echo technique was developed. The method yields co-registered lipid and water images of the heart from data acquired in a single breath hold, producing data with optimal contrast between lipid and myocardium as well as minimal artifacts caused by chemical shift and blood flow.A technique combining GRAdient and Spin-Echo (GRASE) data acquisition and an iterative algorithm for lipid-water separation (Iterative Decomposition of water and fat with Echo Asymmetry and Least-squares estimation, IDEAL) was also developed. By shifting the typical GRASE data acquisition and employing correction for phase errors due to eddy currents, the IDEAL-GRASE technique achieves more time-efficient and robust lipid-water decomposition in the presence of field inhomogeneities. The technique was developed to acquire data for Cartesian and radial k-space trajectories. The radial IDEAL-GRASE with auto-correction of phase errors was developed to accomplish insensitivity to motion artifacts as well as for the generation of high resolution parametric maps (T2 and T2) for tissue characterization.A radial "variable flip angle" Steady-State Free Precession (SSFP) technique with slice profile correction was also developed to obtain fast estimation of another parameter, i.e. the T1/T2 value. This method was developed as an alternative for fast parametric imaging.These body MRI techniques were evaluated in phantoms, healthy volunteers, and patients and demonstrated for a series of applications including pelvic, cardiac, abdominal, and musculoskeletal imaging.

APA, Harvard, Vancouver, ISO, and other styles

49

Placidi, Elisa. "Magnetic resonance imaging of colonic function." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/13886/.

Full text

Abstract:

The overall aim of this work was to develop MRI methods and techniques to study the physiology and the pathology of the gastrointestinal tract, with particular attention to the colon. Besides, the development of new methods was aimed in order to perform quantitative analysis using proton and fluorine MRI. In particular the first experimental chapter describes the development and the optimisation of imaging protocols for studying colonic function in undisturbed physiologically relevant conditions. In addition a texture analysis method based on Gabor filters is developed and used for the objective assessment of colonic content characteristics. The mechanisms of action of common anti-diarrhoeal and anti-constipation agents are also investigated. The last experimental chapter describes the development of methods for using markers to measure GI transit. Transit time, i.e. the time it takes for a marker to pass through the entire gut, is often affected by functional gastrointestinal disorders, therefore it is of primary importance to develop a non-invasive and effective technique for the diagnosis of such gastrointestinal diseases. The use of fluorinated agents and its many advantages compared to other techniques is outlined and the first in vivo studies at high field are presented. The use of gadolinium based compounds as an additional marker is also discussed.

APA, Harvard, Vancouver, ISO, and other styles

50

Noterdaeme, Olivier. "Magnetic Resonance Imaging of the Liver." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490296.

Full text

Abstract:

In this thesis, we develop image analysis techniques, applied and tested in a clinical environment, to support the management of patients with (metastatic) liver cancer The incidence of this cancer is rising and represents approximately 10% of cancer cases in men and women. Image analysis of the liver is difficult, in part because it is the only organ mixing arterial and (portal) venous blood, and in part because of the large excursion it is undergoing during respiration.

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Neurology; Magnetic resonance imaging'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles