Дисертації з теми "Brain Magnetic resonance imaging Statistical methods"
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Ash, Thomas William John. "Use of statistical classifiers in the analysis of fMRI data." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609710.
Повний текст джерелаRoura, Pérez Eloy. "Automated methods on magnetic resonance brain imaging in multiple sclerosis." Doctoral thesis, Universitat de Girona, 2016. http://hdl.handle.net/10803/394030.
Повний текст джерелаEn aquesta tesi ens centrem, per una part, en el pre-processat de la imatge per tal d'eliminar el soroll i corregir les inhomogeneïtats en les intensitats, ambdós errors introduïts per l'escàner. A més hem contribuït també amb una nova tècnica basada en un algoritme de “región growing” per tal de segmentar el cervell de dins de tota la imatge del cap. Incloem com a pre-processat el registre d'imatges, on hem proposat una “pipeline" mitjançant la informació de múltiples modalitats per tal de millorar els resultats d'aquest procés. Per altra banda, hem estudiat també les tècniques actuals de detecció i segmentació de lesions en la matèria blanca, proposant un mètode nou basat en anteriors propostes. Així doncs, presentem una eina automàtica capaç de detectar i segmentar lesions en la matèria blanca de pacients d'Esclerosi Múltiple i Lupus.
Streitbürger, Daniel-Paolo. "Investigating Brain Structure Using Voxel-Based Methods with Magnetic Resonance Imaging." Doctoral thesis, Universitätsbibliothek Leipzig, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-132638.
Повний текст джерелаGrieve, Stuart Michael. "Development of fast magnetic resonance imaging methods for investigation of the brain." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365824.
Повний текст джерелаWoo, Bo-kei, and 胡寶琦. "A new hierarchical Bayesian approach to low-field magnetic resonance imaging." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31226917.
Повний текст джерелаBuchanan, Colin Richard. "Structural brain networks from diffusion MRI : methods and application." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/14183.
Повний текст джерелаStelzer, Johannes. "Nonparametric statistical inference for functional brain information mapping." Doctoral thesis, Universitätsbibliothek Leipzig, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-143884.
Повний текст джерелаMyllylä, T. (Teemu). "Multimodal biomedical measurement methods to study brain functions simultaneously with functional magnetic resonance imaging." Doctoral thesis, Oulun yliopisto, 2014. http://urn.fi/urn:isbn:9789526205076.
Повний текст джерелаTiivistelmä Multimodaalisia kuvantamismenetelmiä käytetään enenevässä määrin ihmisen fysiologian ja elintoimintojen tutkimisessa. Erityisesti aivotutkimuksessa samanaikaisesti useammalla modaliteetilla mittaaminen mahdollistaa erilaisten fysiologisten mekanismien ja niiden korrelaatioiden tutkimisen kehon ja aivotoimintojen välillä. Lisäksi multimodaaliset mittaukset auttavat yksilöimään fysiologiset komponentit toisistaan ja identifioimaan aivojen tuottamia fysiologisia signaaleja. Tämä väitöskirja kokoaa tutkimustyön sekä laite- ja instrumentointisuunnittelun ja sen kehittämistyön ei-invasiivisesti toteutettujen lääketieteen mittausmenetelmien käyttämiseksi magneettikuvauksen aikana. Erityishaasteena työssä on ollut magneettikuvausympäristö, joka asettaa erityisvaatimuksia mm. mittalaitteissa käytettäville materiaaleille sekä laitteiden häiriönsiedolle magneettikuvauslaitteen aiheuttaman voimakkaan magneettikentän takia. Kehitettävät mittausmenetelmät eivät myöskään saa aiheuttaa häiriöitä magneettikuvauslaitteen tuottamalle kuvainformaatiolle. Väitöskirjassa esitettävät mittausmenetelmät tekevät mahdolliseksi mitata magneettikuvausympäristössä ihmisen sydämen sykettä, veren virtauksen kulkunopeutta ja verenpaineen vaihteluja sekä aivokuoren metaboliaa - kaikki synkronissa aivosähkökäyrän mittaamisen ja magneettikuvantamisen kanssa. Lisäksi väitöskirjassa tutkitaan kehitettyjen mittausmenetelmien antamaa mittaustarkkuutta sekä arvioidaan lähi-infrapunavalon etenemistä ihmisen aivoissa uudenlaisella menetelmällä. Kehitetyllä multimodaalisella mittausympäristöllä on tavoitteena antaa lääketieteen alan tutkijoille, erityisesti neurologeille, käyttöön mittausmenetelmiä, joiden avulla voidaan tutkia ihmisen aivojen ja kehon välisiä toimintoja aiempaa kattavammin. Laitekokonaisuudella on tutkittu jo yli 70:tä henkilöä. Näissä mittauksissa on tutkittu mm. veren happitasojen hitaita vaihteluja ihmisen aivojen ollessa lepotilassa, ns. resting state -tilassa
Clayden, Jonathan D. "Comparative analysis of connection and disconnection in the human brain using diffusion MRI : new methods and applications." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/2383.
Повний текст джерелаTaljan, Kyle Andrew Ignatius. "Investigations of Anatomical Connectivity in the Internal Capsule of Macaques with Diffusion Magnetic Resonance Imaging." Cleveland State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=csu1311093061.
Повний текст джерелаPuddephat, Michael J. "Computer interface for convenient application for stereological methods for unbiased estimation of volume and surface area : studies using MRI with particular reference to the human brain." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368022.
Повний текст джерелаStreitbürger, Daniel-Paolo [Verfasser], Matthias [Akademischer Betreuer] Schroeter, Karsten [Akademischer Betreuer] Müller, and Anonym [Gutachter] Anonym. "Investigating Brain Structure Using Voxel-Based Methods with Magnetic Resonance Imaging / Daniel-Paolo Streitbürger ; Gutachter: Anonym Anonym ; Matthias Schroeter, Karsten Müller." Leipzig : Universitätsbibliothek Leipzig, 2014. http://d-nb.info/1238600042/34.
Повний текст джерелаDwyer, Michael G. "Development and application of novel algorithms for quantitative analysis of magnetic resonance imaging in multiple sclerosis." Thesis, University of Bradford, 2013. http://hdl.handle.net/10454/6298.
Повний текст джерелаChen, Jacqueline T. 1973. "Image-processing of MRI for measuring brain injury, repair and degeneration in patients with multiple sclerosis." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=113848.
Повний текст джерелаDemyelinated and inflammatory white-matter lesions are hallmark features of MS. A methodology is described to detect regions of acute white-matter lesions that undergo myelin destruction and repair based on analysis of magnetization transfer ratio (MTR) images. Validation is performed based on histopathology and error is assessed based on same-day scans. To quantify the spatial extent and temporal evolution of myelin destruction and repair, data from a 3-year clinical trial is analyzed using this method. Approximately 20% of acute lesion voxels show some repair over the initial 7 months. In subsequent months, there is little further repair, but some increases in the lesion volume undergoing demyelination.
Although less conspicuous on conventional MRI, there is considerable MS pathology in the brain tissue outside of white-matter lesions. An image-processing methodology was developed to obtain accurate metrics that quantify change over time in whole-brain MTR (associated with changes in myelin-density) and in T2 relaxation time (associated with changes in inflammatory edema). These metrics, in addition to metrics of brain atrophy and axonal integrity, were used to quantify brain injury and degeneration following immunoablation and autologous hematopoietic stem cell transplantation therapy for MS. Pronounced brain volume loss was detected immediately following therapy, associated with decreased myelin density and not resolution of edema.
Post-mortem histopathology has revealed abnormalities in the cortical grey-matter of MS patients that appear to be independent of white-matter lesions. A methodology to quantify neocortical injury and degeneration that yields cross-sectional and longitudinal metrics of cortical thickness and grey-matter/white-matter interface integrity both globally and regionally is presented and validated. MS patients with progressive disability showed greater decreases in cortical metrics compared to MS patients with stable disability.
The quantitative MRI analysis methods presented in this thesis are applicable to MRI data obtained in clinical trials of therapies for MS, have the necessary sensitivity and specificity to assess therapeutic efficacy, and provide new insights into disease pathogenesis and evolution.
Belzycki, Sari E. "Measurement of brain atrophy in pediatric patients with clinically isolated demyelinating syndromes and multiple sclerosis." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112380.
Повний текст джерелаSIENA was used to observe atrophy in children who have experienced a Clinically Isolated Syndrome (CIS) of the type leading to MS (CIS-MS). Brain atrophy was present within the first three months after a CIS event, and then subsided over the rest of the year. If the first acute episode was excluded, there was no significant difference in atrophy rates between the CIS-MS group and the CIS group, and no significant difference between those with T2-weighted brain lesions versus those who had none.
Denolin, Vincent. "Sources of contrast and acquisition methods in functional MRI of the human brain." Doctoral thesis, Universite Libre de Bruxelles, 2002. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211408.
Повний текст джерелаL'Imagerie fonctionnelle par Résonance Magnétique (IRMf) a connu un développement important depuis sa découverte au début des années 1990. Basée le plus souvent sur l'effet BOLD (Blood Oxygenation Level Dependent), cette technique permet d'obtenir de façon totalement non-invasive des cartes d'activation cérébrale, avec de meilleures résolutions spatiale et temporelle que les méthodes préexistantes telles que la tomographie par émission de positrons (TEP). Facilement praticable au moyen des imageurs par RMN disponible dans les hôpitaux, elle a mené à de nombreuses applications dans le domaine des neurosciences et de l'étude des pathologies cérébrales.
Il est maintenant bien établi que l'effet BOLD est dû à une augmentation de l'oxygénation du sang veineux dans les régions du cerveau où se produit l'activation neuronale, impliquant une diminution de la différence de susceptibilité magnétique entre le sang et les tissus environnants (la déoxyhémoglobine étant paramagnétique et l'oxyhémoglobine diamagnétique), et par conséquent un augmentation du signal si la méthode d'acquisition est sensible aux inhomogénéités de champ magnétique. Cependant, il reste encore de nombreuses inconnues quant aux mécanismes liant les variations d'oxygénation, de flux et de volume sanguin à l'augmentation de signal observée, et la dépendance du phénomène en des paramètres tels que l'intensité du champ, la résolution spatiale, et le type de séquence de RMN utilisée. La première partie de la thèse est donc consacrée à l'étude de l'effet BOLD, dans le cas particulier des contributions dues aux veines de drainage dans les séquences de type écho de gradient rendues sensibles au mouvement par l'ajout de gradients de champ. Le modèle développé montre que, contrairement au comportement suggéré par de précédentes publications, l'effet de ces gradients n'est pas une diminution monotone de la différence de signal lorsque l'intensité des gradients augmente. D'importantes oscillations sont produites par l'effet de phase dû au déplacement des spins du sang dans les gradients additionnels, et par la variation de cette phase suite à l'augmentation du flux sanguin. La validation expérimentale du modèle est réalisée au moyen de la séquence PRESTO (Principles of Echo-Shifting combined with a Train of Observations), c'est-à-dire une séquence en écho de gradient où des gradients supplémentaires permettent d'augmenter la sensibilité aux inhomogénéités de champ, et donc à l'effet BOLD. Un accord qualitatif avec la théorie est établi en montrant que la variation de signal observée peut augmenter lorsqu'on intensifie les gradients additionnels.
Un autre source de débat continuel dans le domaine de l'IRMf réside dans l'optimalisation des méthodes d'acquisition, au point de vue notamment de leur sensibilité à l'effet BOLD, leurs résolutions spatiale et temporelle, leur sensibilité à divers artefacts tels que la perte de signal dans les zones présentant des inhomogénéités de champ à grande échelle, et la contamination des cartes d'activation par les contributions des grosses veines, qui peuvent être distantes du lieu d'activation réel. Les séquences en écho de spin sont connues pour être moins sensibles à ces deux derniers problèmes, c'est pourquoi la deuxième partie de la thèse est consacrée à une nouvelle technique permettant de donner une pondération T2 plutôt que T2* aux images. Le principe de base de la méthode n'est pas neuf, puisqu'il s'agit de la « Préparation T2 » (T2prep), qui consiste à atténuer l'aimantation longitudinale différemment selon la valeur du temps de relaxation T2, mais il n’avait jamais été appliqué à l’IRMf. Ses avantages par rapport à d’autres méthodes hybrides T2 et T2* sont principalement le gain en résolution temporelle et en dissipation d’énergie électromagnétique dans les tissus. Le contraste généré par ces séquences est étudié au moyen de solutions stationnaires des équations de Bloch. Des prédictions sont faites quant au contraste BOLD, sur base de ces solutions stationnaires et d’une description simplifiée de l’effet BOLD en termes de variations de T2 et T2*. Une méthode est proposée pour rendre le signal constant au travers du train d’impulsions en faisant varier l’angle de bascule d’une impulsion à l’autre, ce qui permet de diminuer le flou dans les images. Des expériences in vitro montrent un accord quantitatif excellent avec les prédictions théoriques quant à l’intensité des signaux mesurés, aussi bien dans le cas de l’angle constant que pour la série d’angles variables. Des expériences d’activation du cortex visuel démontrent la faisabilité de l’IRMf au moyen de séquences T2prep, et confirment les prédictions théoriques quant à la variation de signal causée par l’activation.
La troisième partie de la thèse constitue la suite logique des deux premières, puisqu’elle est consacrée à une extension du principe de déplacement d’écho (echo-shifting) aux séquences en écho de spin à l’état stationnaire, ce qui permet d’obtenir une pondération T2 et T2* importante tout en maintenant un temps de répétition court, et donc une bonne résolution temporelle. Une analyse théorique approfondie de la formation du signal dans de telles séquences est présentée. Elle est basée en partie sur la technique de résolution des équations de Bloch utilisée dans la deuxième partie, qui consiste à calculer l’aimantation d’état stationnaire en fonction des angles de précession dans le plan transverse, puis à intégrer sur les isochromats pour obtenir le signal résultant d’un voxel (volume element). Le problème est aussi envisagé sous l’angle des « trajectoires de cohérence », c’est-à-dire la subdivision du signal en composantes plus ou moins déphasées, par l’effet combiné des impulsions RF, des gradients appliqués et des inhomogénéités du champ magnétique principal. Cette approche permet d’interpréter l’intensité du signal dans les séquences à écho déplacé comme le résultat d’interférences destructives entre diverses composantes physiquement interprétables. Elle permet de comprendre comment la variation de la phase de l’impulsion d’excitation (RF-spoiling) élimine ces interférences. Des expériences in vitro montrent un accord quantitatif excellent avec les calculs théoriques, et la faisabilité de la méthode in vivo est établie. Il n’est pas encore possible de conclure quant à l’applicabilité de la nouvelle méthode dans le cadre de l’IRMf, mais l’approche théorique proposée a en tout cas permis de revoir en profondeur les mécanismes de formation du signal pour l’ensemble des méthodes à écho déplacé, puisque le cas de l’écho de gradient s’avère complètement similaire au cas de l’écho de spin.
La thèse évolue donc progressivement de la modélisation de l’effet BOLD vers la conception de séquences, permettant ainsi d’aborder deux aspects fondamentaux de la physique de l’IRMf.
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished
Salem, Mostafa. "Deep learning methods for automated detection of new multiple sclerosis lesions in longitudinal magnetic resonance images." Doctoral thesis, Universitat de Girona, 2020. http://hdl.handle.net/10803/668990.
Повний текст джерелаEsta tesis se centra en el desarrollo de métodos novedosos y totalmente automatizados para la detección de nuevas lesiones de esclerosis múltiple en la resonancia magnética longitudinal del cerebro. Primero, propusimos un marco totalmente automatizado basado en la regresión logística para la detección y segmentación de nuevas lesiones T2-w. El marco se basaba en la sustracción de intensidad y el campo de deformación (DF). En segundo lugar, propusimos un enfoque de red neuronal totalmente convolucional para detectar nuevas lesiones T2-w en imágenes de resonancia magnética del cerebro longitudinal. El modelo se entrenó de extremo a extremo y aprendió simultáneamente tanto los DF como las nuevas lesiones T2-w. Por último, propusimos un enfoque basado en el aprendizaje profundo para la síntesis de las lesiones de la EM, a fin de mejorar el rendimiento de la detección y la segmentación de las lesiones tanto en el análisis transversal como en el longitudinal
Chen, Joyce Lynn. "The neural basis for auditory-motor interactions during musical rhythm processing." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=108586.
Повний текст джерелаL’interaction entre le son et le mouvement n’est pas seulement essentielle lors de prestations musicales, mais aussi lors de l’ acquisition de la parole, et pourrait être à la base du succès de la musique lorsqu’elle est utilisée en tant qu’agent thérapeutique visant la facilitation du mouvement. Cette dissertation consiste en trois études d’imagerie par résonance magnétique fonctionnelle visant à élucider les fondements neuraux à la base de l’interaction entre le système auditif et le système moteur dans le contexte de la perception et de la production de rythmes musicaux. La première étude examina les corrélats neuraux facilitant le couplage auditif-moteur chez des sujets produisant des battements alors qu’ils étaient guidés par un rythme isochronique. L’information auditive fut manipulée pour que la proéminence métrique du rythme isochronique augmente à travers cinq niveaux paramétriques dans le but de moduler les battements produits par le sujet. [...]
Shymanskaya, Aliaksandra [Verfasser], N. Jon [Akademischer Betreuer] Shah, Achim [Akademischer Betreuer] Stahl, and Armin [Akademischer Betreuer] Nagel. "Development and implementation of novel experimental methods for the quantification of the healthy and diseased brain by means of sodium magnetic resonance imaging / Aliaksandra Shymanskaya ; Nadim Joni Shah, Achim Stahl, Armin Nagel." Aachen : Universitätsbibliothek der RWTH Aachen, 2020. http://d-nb.info/1217503684/34.
Повний текст джерелаShymanskaya, Aliaksandra Verfasser], N. Jon [Akademischer Betreuer] [Shah, Achim [Akademischer Betreuer] Stahl, and Armin [Akademischer Betreuer] Nagel. "Development and implementation of novel experimental methods for the quantification of the healthy and diseased brain by means of sodium magnetic resonance imaging / Aliaksandra Shymanskaya ; Nadim Joni Shah, Achim Stahl, Armin Nagel." Aachen : Universitätsbibliothek der RWTH Aachen, 2020. http://d-nb.info/1217503684/34.
Повний текст джерелаSchwartz, Yannick. "Large-scale functional MRI analysis to accumulate knowledge on brain functions." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112056/document.
Повний текст джерелаHow can we accumulate knowledge on brain functions? How can we leverage years of research in functional MRI to analyse finer-grained psychological constructs, and build a comprehensive model of the brain? Researchers usually rely on single studies to delineate brain regions recruited by mental processes. They relate their findings to previous works in an informal way by defining regions of interest from the literature. Meta-analysis approaches provide a more principled way to build upon the literature. This thesis investigates three ways to assemble knowledge using activation maps from a large amount of studies. First, we present an approach that uses jointly two similar fMRI experiments, to better condition an analysis from a statistical standpoint. We show that it is a valuable data-driven alternative to traditional regions of interest analyses, but fails to provide a systematic way to relate studies, and thus does not permit to integrate knowledge on a large scale. Because of the difficulty to associate multiple studies, we resort to using a single dataset sampling a large number of stimuli for our second contribution. This method estimates functional networks associated with functional profiles, where the functional networks are interacting brain regions and the functional profiles are a weighted set of cognitive descriptors. This work successfully yields known brain networks and automatically associates meaningful descriptions. Its limitations lie in the unsupervised nature of this method, which is more difficult to validate, and the use of a single dataset. It however brings the notion of cognitive labels, which is central to our last contribution. Our last contribution presents a method that learns functional atlases by combining several datasets. [Henson 2006] shows that forward inference, i.e. the probability of an activation given a cognitive process, is often not sufficient to conclude on the engagement of brain regions for a cognitive process. Conversely, [Poldrack 2006] describes reverse inference as the probability of a cognitive process given an activation, but warns of a logical fallacy in concluding on such inference from evoked activity. Avoiding this issue requires to perform reverse inference with a large coverage of the cognitive space. We present a framework that uses a "meta-design" to describe many different tasks with a common vocabulary, and use forward and reverse inference in conjunction to outline functional networks that are consistently represented across the studies. We use a predictive model for reverse inference, and perform prediction on unseen studies to guarantee that we do not learn studies' idiosyncrasies. This final contribution permits to learn functional atlases, i.e. functional networks associated with a cognitive concept. We explored different possibilities to jointly analyse multiple fMRI experiments. We have found that one of the main challenges is to be able to relate the experiments with one another. As a solution, we propose a common vocabulary to describe the tasks. [Henson 2006] advocates the use of forward and reverse inference in conjunction to associate cognitive functions to brain regions, which is only possible in the context of a large scale analysis to overcome the limitations of reverse inference. This framing of the problem therefore makes it possible to establish a large statistical model of the brain, and accumulate knowledge across functional neuroimaging studies
Boux, Fabien. "Méthodes statistiques pour l'imagerie vasculaire par résonance magnétique : application au cerveau épileptique." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALM068.
Повний текст джерелаThe objective of this thesis is the investigation of magnetic resonance imaging (MRI) for the identification and localization of brain regions involved in mesio-temporal lobe epilepsy (MTLE). Precisely, the work aims 1) at optimizing a vascular MRI protocol on an animal model of epilepsy and 2) at designing a method to quantify vascular MRI maps based on the modeling of the relationship between MRI signals and biophysical parameters.MRI acquisitions on an experimental mouse model of MTLE with hippocampal sclerosis were performed on a 9.4 T scanner. The data collected allowed the quantification of seven cellular and vascular MRI maps a few days after the epileptic condition and later when the spontaneous seizures emerged. These parameters were used for the automatic identification of epileptogenic regions and regions of seizure propagation. To enhance the detection of small variations in MRI parameters in epileptic subjects, a quantification method based on magnetic resonance fingerprinting has been developed. This method consists in identifying, among a set of simulated signals, the closest one to the acquired signal. It can be seen as an inverse problem that presents the following difficulties: the direct model is non-linear, as a complex series of equations or simulation tools; the inputs are high-dimensional signals; and the output is multidimensional. For these reasons, we used an appropriate inverse regression approach to learn a mapping between signal and biophysical parameter spaces. In a field widely dominated by deep learning approaches, the proposed method is very competitive and provides more accurate results. Moreover, the method allows for the first time to produce a confidence index associated with each estimate. In particular, this index allows to reduce the quantification error by discarding estimates associated with low confidence.So far no clinical protocol emerges as a consensus to accurately localize epileptic foci. The possibility of a non-invasive identification of these regions is therefore a first step towards a potential clinical transfer
Bordalo-Rodrigues, Marcelo. "Avaliação da acurácia da ressonância magnética no diagnóstico das lesões traumáticas do plexo braquial." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/5/5151/tde-06062016-093859/.
Повний текст джерелаBrachial plexus injury is considered the most severe neural disorder in the extremities and in general resulting from high-energy trauma in young patients, usually involving motor vehicles. For this reason, traumatic brachial plexus injuries are becoming more frequent. This study evaluated the accuracy of magnetic resonance imaging (MRI) in the diagnosis of traumatic brachial plexus injuries in adults, using surgical findings as the gold standard method. We also evaluated the accuracy of diffusion weighted image neurography (DW neurography) compared to conventional MRI and the ability to differentiate the three types of injuries by MRI: avulsion, rupture and lesion-in-continuity. Thirty-three patients with clinical history and diagnosis of traumatic brachial plexus injury were prospectively studied by MRI. MRI findings (obtained with and without use of DW neurography) and clinical examination were compared with intraoperative findings. The statistical analysis was performed with 5% significance association. There was high correlation between MRI with DW neurography and surgery (rs = 0.79) and low correlation between conventional MRI and surgery (rs = 0.41). The interobserver correlation was higher for MRI with DW neurography (rs = 0.94) than for regular MRI (rs = 0.75). The sensitivities, accuracies and positive predictive values were above 95% for MRI (with and without DW neurography) in the evaluation of the entire plexus. The specificities were generally higher for DW neurography (p < 0.05). Regarding the differentiation between types of lesions, MRI with DW neurography demonstrated high accuracies and sensitivities in the diagnosis of avulsion / rupture and high specificity in the diagnosis of lesion-in-continuity. MRI accuracy (93.9%) was significantly higher than clinical examination (76.5%) in diagnosis of brachial plexus traumatic lesions (p < 0.05).
Ramos, Maria Manuela de Andrade e. Silva. "Plano de segurança do paciente para pacientes com sistemas de estimulação encefálica profunda submetidos a exames de imagem por ressonância magnética no Hospital Marcelino Champagnat." Universidade Tecnológica Federal do Paraná, 2016. http://repositorio.utfpr.edu.br/jspui/handle/1/2011.
Повний текст джерелаIn 2013, the National Program Patient Safety (PNSP) was implemented in Brazil through Resolution RDC 36, providing that the Brazilian health institutions must have a Patient Safety Plan (PSP) for situations that may lead to adverse events (AEs), which are unintentional injury or damage caused to the patient by the health care intervention and not by the primary disease. The PSP is a document with scientific basis that points to hazardous situations and describes strategies and actions defined by the health service for risk management in order to prevent and reduce AEs in all phases of patient care. Implantation of Deep Brain Stimulation (DBS) devices is considered a routine procedure at the Hospital Marcelino Champagnat (HMC), located in Curitiba – PR, and it consists in a practice widely used to improve symptoms and quality of life of patients with certain chronic neurological disorders.The reliability and accuracy of the final brain positioning of the leads, after the DBS implantation are of paramount importance to assure efficacy. Currently, post-operative Magnetic Resonance Imaging (MRI) is the gold standard for the documentation of the correct lead positioning. However, the interaction between the DBS system and the MRI radiofrequency field could represent an important source of adverse events (EAs) since it allows electric currents induction with potential to cause local thermal injuries on high resistance sites. The safety recommendations from the DBS system manufacturers for most of the already deployed systems are quite restrictive resulting in long examination times or low quality images, which compromises the practice in many centers. Thus, the present work proposes the development of a PSP based on the manufacturer's safety recommendations and a systematic review of the literature to the specific situation of patients with DBS systems undergoing MRI scans at the HMC. We found a total of 26 papers, that were considered relevant and allowed us to identify the potential sources of risk in order to avoid them, collaborating to the successful elaboration of the PSP. Besides supplying local demand, this work also aims to promote patient safety and draw attention to the need of interposing barriers in order to avoid significant AEs situations that a radiology department may be presented with. Moreover, the methodology proposed here can serve as a basis for other imaging centers to compose their own PSPs.
Streitbürger, Daniel-Paolo. "Investigating Brain Structure Using Voxel-Based Methods with Magnetic Resonance Imaging." Doctoral thesis, 2013. https://ul.qucosa.de/id/qucosa%3A12285.
Повний текст джерелаAndrews-Shigaki, Brian C. "Analysis of segmentation methods for partial volume correction in magnetic resonance spectroscopy voxels." Thesis, 2007. http://hdl.handle.net/10125/20420.
Повний текст джерела"Computational techniques for statistical morphometric analysis of 3-D MRI data of human skull and brain." Thesis, 2008. http://library.cuhk.edu.hk/record=b6074676.
Повний текст джерелаThesis (Ph.D.)--Chinese University of Hong Kong, 2008.
Includes bibliographical references (leaves 171-185).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts in English and Chinese.
"Diffusion tensor MRI predictors of cognitive impairment in confluent white matter lesion." 2012. http://library.cuhk.edu.hk/record=b5549080.
Повний текст джерела為了獲得更具有臨床價值的擴散核磁造影指數,我們首先需要重構腦白質纖維束並沿著重構出的腦白質纖維束採集數值。然而,傳統的腦白質纖維束重構技術對於腦白質病變十分敏感。此外,不同病人所重構出的腦白質纖維束間缺乏映射關係也使我們無法有效進行大樣本統計分析。
在這個課題裡,我們提出了一個可以解決以上問題的一個全新框架。我們將專家標註過功能區的全腦白質纖維束模板配準到各個個體的腦部。此方案可自動生成個體化的全腦白質纖維束以及纖維束的功能區標註。自由形變模型被用於在全局層面對配準進行約束。所重構纖維束的曲率被用於在局部對配準進行約束。為了減輕腦白質病變對配準的影響,我們運用了一種 魯棒的主成分分析手段來檢測被病灶所干擾的纖維束。為了指導這些被干擾纖維束的配準,我們提出了一種全新的沿纖維束的區域特徵作為替代。此外,我們也探究了通過在纖維束上建立坐標系來除去離群纖維已經提供更高相關性的辦法。
我們所提出的框架被運用於一個腦小血管病變的臨床研究。在64個研究對象中約半數是腦白質病變患者。試驗結果證實此算法成功地將全腦白質纖維束模板配準到了所有研究對象上。沿著特定纖維束改採集的指數與認知測試分數的相關性顯著地超越了傳統指數所給出的結果。我們同時也發現沿著不同功能區腦白質纖維改採集的指數與相應的認知測試分數統計相關。
Although age-related white matter lesion(WML)is an important substrate for cognitive impairment in the elderly, the mechanisms whereby WML induces cognitive impairment are uncertain. Recent findings based on small studies suggested that diffusion tensor imaging (DTI) measures might be the most sensitive imaging predictors in patients with WML. Understanding the imaging predictors for such disease will be useful in monitoring disease progression and in devising surrogate marker for treatment trials.
In order to obtain DTI measurements with diagnostic significance, it is first necessary to reconstruct the white-matter fiber pathways inside the brain along which certain DTI-derived values are calculated. Nevertheless, the traditional approach of white-matter tract reconstruction, or tractography, is severely hindered by the abundant existence of lesions inside the brains of WML patients. The lack of correspondence between fiber bundles across patients also makes obtaining group statistics of individual fiber bundles dicult.
In this study, we propose a novel framework that can mitigate the aforementioned issues of traditional tractography approaches. An expert-labeled whole brain tractography template is registered onto individual patients. Fiber trajectories and anatomically meaningful fiber bundles are automatically obtained by this registration. The free-form deformations are used to regularize the transformations at the whole brain level and across fiber bundles. Fiber curvatures are penalized as the intra-fiber regularization to encourage the smoothness of transformed fibers. White matter (WM) lesion is one of the major factors affecting tractography and registration of subjects with neuro Logical disorders. The Robust Principal Component Analysis(RPCA) is used to automatically detect fiber tract segments that are affected by WM lesion and a novel along-fiber regional prior is learned from healthy subjects to facilitate the registration of these fiber tract segments. We also propose to establish bundle-wise coordinate system by utilizing low-rank constraints upon the DTI measurements. The eort elevates the summary for an anatomical bundle from a scalar statistic to a vector containing changes along the representative fiber pathway. It provides means to exclude the outlier fibers while retaining partially-complete fibers.
The proposed scheme is applied to a clinical study of cerebral small vessel diseases(SVD).Experimental results show successful registration of the whole brain tractography template onto all 64 subjects, including both healthy con¬trol subjects and SVD patients. The DTI measures measured along specific registered anatomical fiber bundles exhibit significant boost in correlation with cognitive functions as compared with traditional measures. It also shows that different anatomical WM structures correlate with multiple types of cognitive functions in different ways.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
He, Xiaotian.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2012.
Includes bibliographical references (leaves 46-53).
Abstracts also in Chinese.
List of Figures --- p.ix
List of Tables --- p.xii
Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Motivation --- p.1
Chapter 1.2 --- Our Work and Contributions --- p.2
Chapter 1.3 --- Related Work --- p.4
Chapter 1.4 --- Thesis Organization --- p.5
Chapter 2 --- Background --- p.6
Chapter 2.1 --- Background of Neuroanatomy --- p.6
Chapter 2.2 --- Background on Diffusion Tensor Magnetic Resonance Imaging (DTMRI) --- p.11
Chapter 3 --- Free Form Fibers --- p.18
Chapter 3.1 --- DTI Acquisition --- p.20
Chapter 3.2 --- Fiber Model --- p.20
Chapter 3.3 --- Fiber-to-DTI Registration --- p.21
Chapter 3.3.1 --- Free-Form Fibers (FFFs) --- p.21
Chapter 3.3.2 --- Tensor-Driven Fiber-to-DTI Registration --- p.23
Chapter 3.3.3 --- Reliability Assessment by Robust Principal Component Analysis --- p.24
Chapter 3.3.4 --- Contextual Feature --- p.26
Chapter 3.3.5 --- Learning the Fiber Context Prior --- p.29
Chapter 3.3.6 --- Registration Refinement Using the Fiber Context Prior --- p.29
Chapter 4 --- Results --- p.31
Chapter 5 --- Future Work --- p.39
Chapter 5.1 --- Refinement on Large Bundles --- p.39
Chapter 5.2 --- Outlier Fiber Removal in Fiber Template --- p.40
Chapter 6 --- Conclusion --- p.44
Bibliography --- p.46
Lin, Chien-Nan, and 林建男. "Using Edge Detection Methods to Resolve A Partial Volume Problem for Magnetic Resonance Brain Imaging." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/69639064835210884426.
Повний текст джерела國立中興大學
通訊工程研究所
100
Support vector machine (SVM) has found great promise in magnetic resonance analysis recently. It works effectively depend on choosing proper parameter and kernel. However, there are two major challenge issues in SVM classification. One is the random select of training sample cause unstable and inconsistent result. It may lead to large variation from every experiment. The other is that classification errors via SVM usually distributed at the boundary between classes which is caused by partial volume effect. In this thesis, we have developed a new version of SVM, called iterative SVM (ISVM) that we could take only a few training samples to solve first issue. And using morphological or edge detection processing to deal with second issue, the idea is through above methods to find the boundary between classes. Then extract these areas from MR images for SVM to classify again. We combined above approaches with a preprocessing independent component analysis to improve SVM classification. And choose weighted RBF kernel instead of RBF kernel in SVM. The experimental results show the proposed method has great performance in magnetic resonance brain image classification.
Evans, Jennifer Wai. "Methods and Motion in Paediatric fMRI." Thesis, 2009. http://hdl.handle.net/1807/19029.
Повний текст джерелаSpring, Robyn. "Extracting FMRI Brain Patterns Significantly Related to Behavior via Individual Preprocessing Pipeline Optimization." Thesis, 2012. http://hdl.handle.net/1807/33517.
Повний текст джерелаStelzer, Johannes. "Nonparametric statistical inference for functional brain information mapping." Doctoral thesis, 2013. https://ul.qucosa.de/id/qucosa%3A12468.
Повний текст джерелаTu, Tao. "Machine Learning Methods for Fusion and Inference of Simultaneous EEG and fMRI." Thesis, 2020. https://doi.org/10.7916/d8-0sy9-9r38.
Повний текст джерелаMongerson, Chandler Rebecca Lee. "Probing resting-state functional connectivity in the infant brain: methods and potentiality." Thesis, 2017. https://hdl.handle.net/2144/23837.
Повний текст джерела"Neural Activity Mapping Using Electromagnetic Fields: An In Vivo Preliminary Functional Magnetic Resonance Electrical Impedance Tomography (fMREIT) Study." Doctoral diss., 2020. http://hdl.handle.net/2286/R.I.62811.
Повний текст джерелаDissertation/Thesis
Doctoral Dissertation Biomedical Engineering 2020
Γεωργιάδης, Παντελής. "Computer assisted diagnosis of brain tumors based on statistical methods and pattern recognition techniques." Thesis, 2010. http://nemertes.lis.upatras.gr/jspui/handle/10889/4012.
Повний текст джерелаThe process of brain tumor characterization requires a rather intricate assessment of the various Magnetic Resonance (MR) image and spectroscopic features and is typically performed by experienced radiologists. Despite the inherently subjective nature of many of the decisions associated with this process, an expert radiologist is able to perform this task with a significant degree of precision and accuracy. However, in the effort to deliver more effective treatment, clinicians are continuously seeking for greater accuracy in the pathological characterization of brain tissues. The aim of the present thesis was to design, implement, and evaluate a software classification system for discriminating between different brain tumor types on Magnetic Resonance Imaging (MRI), employing textural and spectroscopic features. The clinical material consisted of sixty seven T1-weighted post-contrast MR brain images (21 metastases, 19 meningiomas, and 27 gliomas), obtained from patients with verified and untreated intracranial tumors. Thirty-six 2-dimensional textural features (2D), from the image histogram and the co-occurrence and run-length matrices, were extracted from each one of 67 MR-images. Similarly, an equal number of 3-dimensional textural features (3D) were also calculated in the attempt to maximize classification performances. Finally, MR-spectroscopy features were also incorporated for improving classification accuracies. Classification methods employed included i/ a modified Probabilistic Neural Network (PNN) and Support Vector Machines (SVM) algorithms, incorporating a non-linear Least Squares Features Transformation (LSFT) into the classifiers and ii/ an ensemble classification scheme employing the LSFT-SVM classifier. The LSFT improved classifiers’ performances, increased class separability, and resulted in dimensionality reduction. For evaluating the performance of the designed classification schemes, evaluations were performed by means of the external cross validation process, which is considered indicative of the generalization performance of the designed classification system to ‘unseen’ cases. It was found that the LSFT features transformation enhanced the performance of the PNN and SVM algorithms, achieving classification accuracies of 73.48 % in distinguishing metastatic from primary tumors and 88.67% in discriminating gliomas from meningiomas. When volumetric 3-dimensional features were employed, these results improved to 88.18% for discriminating between metastatic and primary tumors and 97.33% for distinguishing gliomas from meningiomas. The textural features employed in the design of the optimum classification scheme were associated primarily with image texture homogeneity. Finally, when MR-spectroscopy features were also incorporated, classification accuracy was boosted up from 95% in discriminating meningiomas from metastasis to 100%. The MR-image features that participated in the optimum feature vector were related to the degree of homogeneity, the amount of randomness and the dispersion of the gray-tone intensity values within the texture of the tumor. These textural characteristics are related to textural parameters that physicians employ in diagnosis and they were proportional to the textural imprint of brain tumors, i.e. gliomas have heterogeneous texture while meningiomas appear to be homogeneous in MR imaging. The MR-spectroscopy feature that participated in the optimum feature vector was the Choline (Cho) / N-Acetyl Aspartate (NAA) metabolite integral ratio. It was found that both meningiomas and metastases are characterized from low concentrations of NAA while meningiomas exhibit higher concentrations of Cho than metastases, which could be attributed to increased synthesis of tumor cell membranes. Finally, the proposed system might be of value as an assisting tool for brain tumor characterization on volumetric MRI series.
Lacerda, Luís Miguel Rosa Sousa Prado de. "HARDI Methods: tractography reconstructions and automatic parcellation of brain connectivity." Master's thesis, 2012. http://hdl.handle.net/10451/7944.
Повний текст джерелаA neuroanatomia humana tem sido objecto de estudo científico desde que surgiu o interesse na organização do corpo humano e nas suas funções, quer como um todo quer através das partes que o constituem. Para atingir este fim, as autópsias foram a primeira forma de revelar algum conhecimento, o qual tem vindo a ser catalogado e sistematizado à medida que a medicina evolui. Passando por novas técnicas de conservação e tratamento de tecido humano, de que são exemplo as dissecções de Klinger, nas quais se fazem secções de material conservado criogenicamente, bem como por estudos histológicos através da utilização de corantes, conseguiu-se uma forma complementar de realizar estes estudos. Permanecia, no entanto, a impossibilidade de analisar in vivo a estrutura e função dos diferentes sistemas que constitutem o Homem. Com o surgimento das técnicas imagiológicas o diagnóstico e monitorização do corpo humano, bem como das patologias a ele associadas, melhoraram consideravelmente. Mais recentemente, com o aparecimento da ressonância magnética (MRI: do Inglês "Magnetic Resonance Imaging"), tornou-se possível estudar as propriedades magnéticas do tecido, reflectindo as suas características intrínsecas com base na aplicação de impulsos de radiofrequência. Através de ressonância magnética é possível estudar essas propriedades em vários núcleos atómicos, sendo mais comum o estudo do hidrogénio, pois somos maioritariamente consistituídos por água e gordura. Uma vez que só é possível medir variações do campo magnético, aplicam-se impulsos de radiofrequência para perturbar o equilíbrio dos spins e medir os seus mecanismos de relaxação, os quais, indirectamente, reflectem a estrutura do tecido. Contudo, o sinal medido é desprovido de qualquer informação espacial. De facto, para podermos proceder a essa quantificação, é necessária a utilização de gradientes de campo magnético, que permitem modificar localmente a frequência de precessão dos protões, através da alteração local do campo magnético, permitindo assim, adquirir o sinal de forma sequencial. A informação obtida constitui uma função variável no espaço e através da transformação de Fourier pode ser quantificada em frequências espaciais, sendo estes dados armazenados no espaço k. O preencimento deste espaço, caracterizado por frequências espaciais, bem como os gradientes de campo magnético que são aplicados, permitem determinar a resolução da imagem que podemos obter, aplicando uma transformação de Fourier inversa. O estudo da ressonância magnética não se restringe à análise da estrutura mas também ao estudo da função e difusão das moléculas de água. A difusão é um processo aleatório, que se traduz pelo movimento térmico das moléculas de água, e o seu estudo permite inferir sobre o estado do tecido e microestrutura associada, de uma forma não invasiva e in vivo. A técnica de imagiologia de ressonância magnética ponderada por difusão (DWI: do Inglês "Diffusion Weighted Imaging") permite o estudo da direccionalidade das moléculas de água e extracção de índices que reflectem directamente a integridade dos tecidos biológicos. De modo a sensibilizar as moléculas de água à difusão, é necessário aplicar sequências de ressonância magnética modificadas, nas quais se aplicam gradientes de campo magnético de difusão para quantificar o deslocamento das moléculas e a sua relação com o coeficiente de difusão das mesmas. Num ambiente livre e sem barreiras a difusão das moléculas de água é isotrópica, uma vez que se apresenta igual em todas as direcções. Todavia, tal não se verifica no corpo humano. A presença destas barreiras leva a que, na verdade, apenas possa ser medido um coeficiente de difusão aparente. Este, por sua vez, traduz a interacção entre as moléculas de água com a microestrutura e, como tal, uma anisotropia na sua difusão. Como caso particular de difusão anisotrópica a nível cerebral, tem-se a difusão das moléculas de água na matéria branca, uma vez que esta apresenta uma direccionalidade preferencial de acordo com a orientação dos axónios, visto estarem presentes menos restrições à sua propagação, ao contrário do que acontece com a direcção perpendicular (devido à membrana celular e às bainhas de mielina). Por oposição, a matéria cinzenta, constituída pelo aglomerado dos corpos celulares dos neurónios, e o líquido cefalorraquidiano apresentam uma difusão sem direcção preferencial (i.e. aproximadamente isotrópica). A informação obtida através da difusão das moléculas de água encontra-se limitada pelo número de direcções segundo o qual aplicamos os gradientes de difusão. Deste modo, surgiu a imagiologia por tensor de difusão (DTI: do Inglês "Diffusion Tensor Imaging"). Esta técnica permite extrair informação acerca da tridimensionalidade da distribuição da difusão de moléculas de água através da aplicação de seis gradientes de difusão não colineares entre si. A distribuição destas moléculas pode, então, ser vista como um elipsóide, no qual o principal vector próprio do tensor representa a contribuição da difusão das moléculas segundo a direcção do axónio (ou paralela), sendo os dois restantes componentes responsáveis pela contribuição transversal. Além da difusividade média (MD: do Inglês "Mean Diffusivity") e das contribuições da difusão paralela (MD//) e perpendicular (MD ) às fibras, é também possível extrair outros índices, como a anisotropia fraccional (FA: do Inglês "Fractional Anisotropy"), que fornece informação acerca da percentagem de difusão anisotrópica num determinado voxel. Para a matéria branca, tal como já foi referido, existe difusão preferencial e, portanto, a anisotropia fraccional será elevada. Por outro lado, para a matéria cinzenta e para o líquido cefalorraquidiano, verificar-se-á uma FA reduzida, devido à ausência de anisotropia. Todavia, regiões com reduzida anisotropia fraccional podem camuflar regiões de conformação de cruzamento de fibras, ou fibras muito anguladas, que a imagiologia por tensor de difusão não consegue resolver. A razão para esta limitação reside no número reduzido de diferentes direcções de difusão que são exploradas, assim como o pressuposto de que a distribuição das moléculas de água é Gaussiana em todo o cérebro, o que não é necessariamente verdade. A fim de se ultrapassar estas limitações, novas técnicas surgiram, nomeadamente as de elevada resolução angular (HARDI: do Inglês "High Angular Resolution Diffusion Imaging"). Estas fazem uso de uma aquisição em função de múltiplas direcções de gradiente e de uma diferente modelação dos dados obtidos, dividindo-se em dois tipos. As técnicas livres de modelos permitem extrair uma função de distribuição da orientação das fibras num determinado voxel directamente do sinal e/ou transformações da função densidade de probabilidade do deslocamento das moléculas de água. Contrariamente, as técnicas baseadas em modelos admitem existir determinados constrangimentos anatómicos e que o sinal proveniente de um determinado voxel é originado por um conjunto de sinais individuais de fibras, caracterizados por uma distribuição preferencial das direcções das fibras. Todos estes métodos têm como objectivo principal recuperar a direcção preferencial da difusão das moléculas de água e reconstruir um trajecto tridimensional que represente a organização das fibras neuronais, pelo que se designam métodos de tractografia. Esta representa a única ferramenta não invasiva de visualização in vivo da matéria branca cerebral e o seu estudo tem revelado uma grande expansão associada ao estabelecimento de marcador biológico para diversas patologias. Adicionalmente, esta técnica tem vindo a tornar-se uma modalidade clínica de rotina e de diversos protocolos de investigação, sendo inclusivamente utilizada para complementar o planeamento em cirurgia, devido à natureza dos dados que gera. Particularmente no caso de dissecções manuais, nas quais os dados de tractografia são manuseados por pessoal especializado, com vista a realizar a parcelização de diferentes tractos de interesse, o processo é moroso e dependente do utilizador, revelando-se necessária a automatização do mesmo. Na realidade, já existem técnicas automáticas que fazem uso de algoritmos de agregação1, nos quais fibras são analisadas e agrupadas segundo características semelhantes, assim como técnicas baseadas em regiões de interesse, em que se extraem apenas os tractos seleccionados entre as regiões escolhidas. O objectivo principal desta dissertação prende-se com a análise automática de dados de tractografia, bem como a parcelização personalizada de tractos de interesse, também esta automática. Em primeiro lugar, foi desenvolvido um algoritmo capaz de lidar automaticamente com funções básicas de carregamento dos ficheiros de tractografia, o seu armazenamento em variáveis fáceis de manusear e a sua filtragem básica de acordo com regiões de interesse de teste. Neste processo de filtragem é feita a avaliação das fibras que atravessam a região de interesse considerada. Assim, após a localização das fibras entre as regiões de interesse os tractos resultantes podem ser guardados de duas formas, as quais têm, necessariamente, que ser especificadas antes de utilizar o software: um ficheiro que contém todas as fibras resultantes da parcelização e outro que contém o mapa de densidade associado, isto é, o número de fibras que se encontra em cada voxel. Após esta fase inicial, a flexibilidade e complexidade do software foi aumentando, uma vez que foram implementados novos filtros e a possibilidade de utilizar regiões de interesse de diferentes espaços anatómicos padrão. Fazendo uma análise a esta última melhoria, pode referir-se que, através de um procedimento de registo não linear da imagem anatómica do espaço padrão ao espaço individual de cada sujeito, foi possível, de forma automática, guardar o campo de deformações que caracteriza a transformação e, assim, gerar regiões de interesse personalizadas ao espaço do sujeito. Estas regiões de interesse serviram depois para a parcelização básica e para seleccionar tractos, mas também para filtragens adicionais, como a exclusão de fibras artefactuosas2 e um filtro especial, no qual apenas os pontos que ligam directamente as diferentes regiões são mantidos. Além do que já foi referido, recorreu-se também à aplicação de planos de interesse que actuam como constrangimentos neuroanatómicos, o que não permite, por exemplo, no caso da radiação óptica, que as fibras se propaguem para o lobo frontal. Esta ferramenta foi utilizada com sucesso para a parcelização automática do Fascículo Arcuado, Corpo Caloso e Radiação Óptica, tendo sido feita a comparação com a dissecção manual, em todos os casos. O estudo do Fasciculo Arcuado demonstrou ser o teste ideal para a ferramenta desenvolvida na medida que permitiu identificar o segmento longo, assim como descrito na literatura. O método automático de duas regiões de interesse deu a origem aos mesmos resultados obtidos manualmente e permitiu confirmar a necessidade de estudos mais aprofundados. Aumentando a complexidade do estudo, realizou-se a parcelização do Corpo Caloso de acordo com conectividade estrutural, isto é, com diferentes regiões envolvidas em funções distintas. Procedeu-se deste modo, e não com base em informação acerca de divisões geométricas, uma vez que estas já demonstraram incongruências quando correlacionadas com subdivisões funcionais. O uso adicional de regiões de interesse para a exclusão de fibras demonstrou-se benéfico na obtenção dos mapas finais. Finalmente, incluiu-se a utilização de um novo filtro para realizar a parcelização da Radiação Óptica, comparando os resultados para DTI e SD(do Inglês "Spherical Deconvolution"). Foi possível determinar limitações na primeira técnica que foram, no entanto, ultrapassadas pela utilização de SD. O atlas final gerado apresenta-se como uma mais-valia para o planeamento cirúrgico num ambiente clínico. O desenvolvimento desta ferramenta resultou em duas apresentações orais em conferências internacionais e encontra-se, de momento, a ser melhorada, a fim de se submeter um artigo de investigação original. Embora se tenha chegado a um resultado final positivo, tendo em conta a meta previamente estabelecida, está aberto o caminho para o seu aperfeiçoamento. Como exemplo disso, poder-se-á recorrer ao uso combinado das duas abordagens de parcelização automática e à utilização de índices específicos dos tractos, o que poderá trazer uma nova força à delineação dos tractos de interesse. Adicionalmente, é também possível melhorar os algoritmos de registo de imagem, tendo em conta a elevada variabilidade anatómica que alguns sujeitos apresentam. Como nota final, gostaria apenas de salientar que a imagiologia por difusão e, em particular, a tractografia, têm ainda muito espaço para progredir. A veracidade desta afirmação traduz-se pela existência de uma grande variedade de modelos e algoritmos implementados, sem que, no entanto, exista consenso na comunidade científica acerca da melhor abordagem a seguir.
Diffusion weighted imaging (DWI) has provided us a non-invasive technique to determine physiological information and infer about tissue microstructure. The human body is filled with barriers affecting the mobility of molecules and preventing it from being constant in different directions (anisotropic diffusion). In the brain, the sources for this anisotropy arise from dense packing axons and from the myelin sheath that surrounds them. Only with Diffusion Tensor Imaging (DTI) it was possible to fully characterize anisotropy by offering estimations for average diffusivities in each voxel. However, these methods were limited, not being able to reflect the index of anisotropic diffusion in regions with complex fibre conformations. It was possible to reduce those problems through the acquisition of many gradient directions with High Angular Resolution Diffusion Imaging (HARDI). There are model-free approaches such as Diffusion Spectrum Imaging (DSI) and Q-ball Imaging (QBI) which retrieve an orientation distribution function (ODF) directly from the water molecular displacement. Another method is Spherical Deconvolution, which is a model-based approach based on the computation of a fibre orientation distribution (FOD) from the deconvolution of the diffusion signal and a chosen fibre response function. Reconstructing the fibre orientations from the diffusion profile, generates a three-dimensional reconstruction of neuronal fibres (Tractography) whether in a deterministic, probabilistic or global way. Tractography has two main purposes: non-invasive and in vivo mapping of human white matter and neurosurgical planning. In order to achieve those purposes it is common to apply parcellation techniques which can be subdivided into ROI-based or Clustering base. The aim of this project is to develop an automated method of tract-based parcellation of different brain regions. This tool is essential to retrieve information about the architecture and connectivity of the brain, overcoming time consuming and expertise related issues derived from manual dissections. Firstly we investigated basic functions to handle diffusion and tractography data. In particular, we focused on how to load track files, filter them according to regions of interest and save the output in different formats. Results were always compared with manual dissection. The developed tool increased complexity by introduction a new filtering and the use of regions of interest from different standard spaces, created trough non-linear registrations. Three major tracts of interest were analysed: Arcuate Fasciculus, Corpus Callosum and Optic Radiation.
"T1rho MRI in brain aging, lumbar disc degeneration, and liver fibrosis: clinical and experimental studies." 2013. http://library.cuhk.edu.hk/record=b5549818.
Повний текст джерела衰老與慢性高血壓是常見腦退行性疾病的兩個主要危險因素。但是正常腦衰老過程及慢性高血壓兩個因素與腦組織T1rho是否有相關性,尚缺乏研究。序貫性測量SD老鼠自5至15月齡、WKY(血壓正常)和SHR(患有自發性高血壓)老鼠自6至12月齡的雙側丘腦、海馬、和皮質的腦組織T1rho值。發現三組老鼠的丘腦、海馬及皮質的T1rho均隨年齡增長而增高;且SHR的顯著高於WKY老鼠。
T1rho值與椎間盤退變等級的相關性已有報導。但相比T2值,T1rho在評價椎間盤退變方面是否優於或如何優於T2值尚缺乏研究。將椎間盤髓核及纖維環的T1rho和T2值與5級和8級椎間盤退變等級系統做比較;發現髓核的T1rho及T2與椎間盤退變等級的相關性均呈二次函數降低,且無顯著差別(P=0.40)。纖維環的T1rho及T2與椎間盤退變等級的相關性呈線性函數降低,T2降低的斜率明顯比T1rho降低的斜率要平坦(P<0.001)。故T1rho值比T2值更加適合評價纖維環退變,而兩者在評價髓核時相似。
肝纖維化是幾乎所有慢性肝病的常見特徵,包括大分子物質在細胞外基質的沉積。選用四氯化碳CCl4腹腔注射6周來製造肝纖維化模型。肝臟T1rho在注射後的第二天輕度上升,然後持續上升,直到注射六周後T1rho達最高值,此後T1rho隨CCl4注射停止而降低。顯示T1rho磁共振成像對於監測慢性注射CCl4誘導的肝纖維化及肝損傷有價值。當沒有明顯肝纖維化時,肝T1rho輕微受水腫及急性炎症的影響。
為將肝臟T1rho磁共振成像轉化到臨床使用,我們研究了其可行性,以及正常志願者肝臟T1rho值分佈範圍。發現採用六個自旋鎖定時間來測量健康志願者肝T1rho,結果有較高的可重複性和一致性,肝T1rho平均值為42.5ms,分佈範圍為38.8到46.5ms。採用三個自鎖鎖定時間點掃描,可以減少一半掃描時間,且可以得到可信的肝T1rho值,但採用兩個自旋鎖定時間點則不行。
T1rho relaxation is spin-lattice relaxation in the rotating frame. It determines the decay of the transverse magnetization in the presence of a spin-lock radiofrequency pulse, which applied along the transverse magnetization. T1rho MRI is sensitive to low frequency motional processes, so it can be used to investigate the interaction between water molecules and their macromolecular environment. T1rho imaging is suggested to have the potential to identify early biochemical changes in tissues.
Aging and chronic hypertension are two major risk factors for common neurodegenerative disease. However, whether normal brain aging and chronic spontaneous hypertensive are associated with brain T1rho values changes were not reported. We longitudinally measured the T1rho value in rat brain of Sprague-Dawley (SD) rats from 5-month to 15-month, and spontaneous hypertensive rats (SHR) with Wistar Kyoto (WKY) rats from 6-month to 12-month. The T1rho values in three brain regions of thalamus, hippocampus, and cortices increased with aging process, and were significantly higher in SHR than WKY rats.
For intervertebral disc, the correlation between T1rho and degenerative grade has been reported. However, whether and how T1rho specifically offer better evaluation of disc degeneration compared with T2 was not studied previously. T1rho and T2 value of nucleus pulposus (NP) and annulus fibrosus (AF) was compared with reference to the five-level and eight-level semi-quantitative disc degeneration grading systems. For NP, T1rho and T2 decreased quadratically with disc degeneration grades and had no significant trend difference (P=0.40). In NP, T1rho and T2 decrease in a similar pattern following disc degeneration. For AF, T1rho and T2 decreased linearly and the slopes of T2 were significantly flatter than those of T1rho (P<0.001). Therefore, the T1rho is better suited for evaluating AF in degenerated disc than T2.
Liver fibrosis, a common feature of almost all causes of chronic liver disease, involves macromolecules accumulated within the extracellular matrix. Male Sprague-Dawley rats received intraperitoneal injection of 2 ml/kg CCl4 twice weekly for up to 6 weeks. Then CCl4 was withdrawn for recovery. The liver T1rho values increased slightly on day 2, then increased further and were highest at week 6 post CCl4 insults, and decreased upon the withdrawal of the CCl4 insult. This study demonstrated that T1rho MRI is a valuable imaging biomarker for liver injury and fibrosis induced by CCl4. Liver T1rho value was only mildly affected by edema and acute inflammation when there was no apparent fibrosis.
To translate liver T1rho MRI to clinical application, the technical feasibility of T1rho MRI in human liver was explored and the normal range of T1rho values in healthy volunteers was determined. We found it is feasible to obtain consistent liver T1rho measurement for healthy human liver with six spin-lock time (SLT) points of 1, 10, 20, 30, 40, and 50ms; the mean liver T1rho value of the healthy subjects was 42.5ms, with a range of 38.8-46.5ms. Adopting 3-SLT points of 1, 20, and 50ms for T1rho measurement could provide reliable measurement and reduce the scanning time, while 2-SLT points of 1 and 50ms do not provide reliable measurement.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Zhao, Feng.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2013.
Includes bibliographical references (leaves 119-143).
Abstracts also in Chinese.
ABSTRACT --- p.i
ACKNOWLEDGEMENTS --- p.vi
LIST OF FIGURES --- p.viii
LIST OF TABLES --- p.xvi
LIST OF ABBREVIATIONS --- p.xvii
CONTENTS --- p.xxi
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Conventional Magnetic Resonance Imaging --- p.1
Chapter 1.1.1 --- Basic Principle of Conventional Magnetic Resonance Imaging --- p.1
Chapter 1.1.2 --- T1 Relaxation --- p.2
Chapter 1.1.3 --- T2 Relaxation --- p.3
Chapter 1.2 --- T1rho Magnetic Resonance Imaging --- p.3
Chapter 1.2.1 --- T1rho Relaxation --- p.3
Chapter 1.2.2 --- Principle of T1rho Magnetic Resonance Imaging --- p.4
Chapter 1.2.3 --- Radiofrequency Pulse for T1rho Magnetic Resonance Imaging --- p.5
Chapter 1.2.4 --- T1rho-weighted Contrast Imaging and Application --- p.10
Chapter 1.2.5 --- Quantitative T1rho Mapping and Application --- p.11
Chapter 1.2.6 --- T1rho Dispersion and Application --- p.13
Chapter 1.3 --- Thesis Overview --- p.14
Chapter Chapter 2 --- T1rho MRI in brain aging of animal model --- p.19
Chapter 2.1 --- Introduction --- p.19
Chapter 2.2 --- Materials and Methods --- p.20
Chapter 2.2.1 --- Animal Model of Brain Aging --- p.20
Chapter 2.2.2 --- T1rho Data Acquisition --- p.21
Chapter 2.2.3 --- T1rho Data Processing --- p.23
Chapter 2.2.4 --- T1rho Measurement and Statistical Analysis --- p.24
Chapter 2.3 --- Results --- p.27
Chapter 2.4 --- Discussion --- p.38
Chapter 2.5 --- Summary --- p.42
Chapter Chapter 3 --- T1rho MRI in lumbar disc degeneration of human subjects --- p.43
Chapter 3.1 --- Introduction --- p.43
Chapter 3.2 --- Methods --- p.45
Chapter 3.2.1 --- Subjects --- p.45
Chapter 3.2.2 --- MR Image Acquisition --- p.46
Chapter 3.2.2.1 --- T2-weighted MRI --- p.46
Chapter 3.2.2.2 --- T2 Mapping Imaging --- p.47
Chapter 3.2.2.3 --- T1rho MRI --- p.47
Chapter 3.2.3 --- Data Processing --- p.49
Chapter 3.2.4 --- Data Measurement and Statistical Analysis --- p.49
Chapter 3.3 --- Results --- p.52
Chapter 3.3.1 --- Range of T1rho/T2 Values for Discs --- p.52
Chapter 3.3.2 --- The Relationship between NP T1rho/T2 Values and 8-level Degeneration Grading of Discs --- p.52
Chapter 3.3.3 --- The Relationship between NP T1rho/T2 Values and 5-level Degeneration Grading of Discs --- p.55
Chapter 3.3.4 --- The Relationship between AF T1rho/T2 Values and 8-level Degeneration Grading of Discs --- p.58
Chapter 3.3.5 --- The Relationship between AF T1rho/T2 Values and 8-level Degeneration Grading of Discs --- p.61
Chapter 3.4 --- Discussion --- p.64
Chapter 3.5 --- Summary --- p.69
Chapter Chapter 4 --- T1rho MRI in rat liver fibrosis model induced by CCl4 insult --- p.71
Chapter 4.1 --- Introduction --- p.71
Chapter 4.2 --- Materials and Methods --- p.73
Chapter 4.2.1 --- Animal Preparation --- p.73
Chapter 4.2.2 --- MR Image Acquisition --- p.74
Chapter 4.2.2.1 --- T2-weighted MRI --- p.75
Chapter 4.2.2.2 --- T1rho MRI --- p.75
Chapter 4.2.3 --- Data Processing --- p.76
Chapter 4.2.4 --- Data Measurement and Statistical Analysis --- p.78
Chapter 4.2.5 --- Histology Analysis --- p.79
Chapter 4.3 --- Results --- p.80
Chapter 4.3.1 --- T1rho Measurement Reproducibility --- p.80
Chapter 4.3.2 --- Rat Liver T1rho Values at Different Time Phase --- p.81
Chapter 4.3.3 --- Relative Rat Liver Signal Intensity on T2WI at Different Time Phase --- p.83
Chapter 4.3.4 --- Histology Results --- p.84
Chapter 4.4 --- Discussion --- p.86
Chapter 4.5 --- Summary --- p.91
Chapter Chapter 5 --- T1rho MRI in liver of healthy human subjects --- p.93
Chapter 5.1 --- Introduction --- p.93
Chapter 5.2 --- Methods --- p.95
Chapter 5.2.1 --- Subjects --- p.95
Chapter 5.2.2 --- MR Image Acquisition --- p.96
Chapter 5.2.2.1 --- T2-weighted MRI --- p.96
Chapter 5.2.2.2 --- T1rho MRI --- p.97
Chapter 5.2.3 --- T1rho Data Processing --- p.99
Chapter 5.2.4 --- T1rho Measurement --- p.100
Chapter 5.3 --- Results --- p.102
Chapter 5.3.1 --- T1rho Measurement Reproducibility --- p.105
Chapter 5.3.2 --- T1rho Value Agreement of the Fasting Status with Post Meal Status --- p.105
Chapter 5.3.3 --- T1rho Value Agreement for T1rho Maps Constructed by Different Spin-lock Time Points --- p.106
Chapter 5.3.4 --- T1rho Value Range of Healthy Human Subjects --- p.108
Chapter 5.4 --- Discussion --- p.108
Chapter 5.5 --- Summary --- p.113
Chapter Chapter 6 --- General discussion and further work --- p.115
References: --- p.119
LIST OF PUBLICATIONS --- p.138
Thiessen, Jonathan. "Development and application of quantitative MRI methods for assessing white matter integrity in the mouse brain." 2012. http://hdl.handle.net/1993/9221.
Повний текст джерелаBelkhatir, Zehor. "Estimation Methods for Infinite-Dimensional Systems Applied to the Hemodynamic Response in the Brain." Diss., 2018. http://hdl.handle.net/10754/627828.
Повний текст джерелаPaula, André Santos. "Usher syndrome: dysfunctional olfactory brain regions and statistical classification of disease status using fMRI." Master's thesis, 2019. http://hdl.handle.net/10316/89802.
Повний текст джерелаO síndrome de Usher (USH) é uma doença autossómica recessiva rara que cursa com alterações da visão e audição apresentando heterogeneidade clínica e genética. Vários estudos psicofísicos e de imagiologia estrutural evidenciaram também a existência de défices olfativos em doentes com USH. No entanto, o efeito desta condição no circuito central de processamento olfativo ainda não foi avaliado através de imagiologia funcional. Deste modo, procurámos comparar a atividade cerebral relacionada com uma tarefa olfativa nos córtices orbito-frontal (COF) e piriforme (CP) entre doentes com USH e indivíduos saudáveis. Além disso, foi realizada uma análise de classificação entre grupos de modo a avaliar o potencial da imagiologia funcional para discriminar doentes com USH de indivíduos saudáveis.Vinte e seis indivíduos saudáveis sem história de disfunção olfativa e 27 doentes com USH (4 USH1, 21 USH2, 2 USH3) foram incluídos neste estudo. Todos os sujeitos realizaram a mesma tarefa de deteção olfativa durante as sessões de ressonância magnética funcional para avaliar as respostas evocadas no COF e CP. Quatro níveis de concentração de butanol foram apresentados a cada participante. As regiões cerebrais foram definidas funcionalmente através do Neurosynth, uma ferramenta de meta-análise automatizada. Na análise univariada foi ajustado um modelo linear geral multi-sujeito com efeitos aleatórios e os parâmetros beta estimados de cada região foram usados para a comparação entre grupos. Na análise de classificação foi ajustado um modelo linear geral com sujeitos separados e foram criados mapas de estatística t para cada sujeito. Estes mapas foram classificados através de um modelo de regressão logística.Verificou-se a existência de um efeito de interação entre o grupo e o nível de butanol no COF direito (F(2,365;118,247)=3,032, p=0,043) e no CP direito (F(3,150)=4,537, p=0,004). Não se verificou nenhum efeito significativo na ativação cerebral evocada pelo estímulo olfativo no COF e CP esquerdos. O contraste planeado da ativação cerebral da maior concentração de odor menos a da menor concentração de odor entre grupos revelou uma diferença significativa no COF direito (t(51)=2,339, p=0,023). O mesmo contraste mostrou uma diferença significativa entre doentes e controlos no CP direito (t(51)=-3.380, p=0.001).Quanto à análise de classificação de doentes versus controlos, apresentamos um modelo preditivo com precisão de 71,7% (p=0,0072), sensibilidade de 67,7% (p=0,0328), especificidade de 77,3% (p=0,0041) e AUC de 0,785 (p=0,0087).Estes resultados evidenciam uma diminuição da ativação no CP direito e um aumento compensatório da ativação no COF direito em doentes com USH reforçando a noção de olfação disfuncional neste síndrome. Além disso, sugerem que os padrões de ativação cerebral em regiões olfativas medidos por ressonância magnética funcional permitem discriminar doentes com USH de indivíduos saudáveis sendo uma técnica promissora em termos de diagnóstico deste síndrome.
Usher syndrome (USH) is a rare autosomal recessive disease, affecting vision and audition, and showing clinical and genetic heterogeneity. Evidence of olfactory impairment in USH patients has emerged through psychophysical and structural imaging studies. However, the effect of this condition in the central olfactory processing network has not yet been evaluated through functional imaging studies. We sought to compare olfactory task-related activity in the orbitofrontal (OFC) and piriform (PC) cortices between USH patients and healthy subjects. Also, a classification analysis between these groups was carried out to assess functional imaging potential of discriminating USH patients.Twenty-six age- and gender-matched controls with no history of olfactory dysfunction and 27 USH patients (4 USH1, 21 USH2, 2 USH3) were studied. Functional magnetic resonance imaging (fMRI) was used with an olfactory detection task to evaluate responses in the OFC and PC. Four butanol concentration levels were presented to each participant. These regions were functionally defined using an automated meta-analysis toolbox, Neurosynth. In the univariate analyses a multi-subject general linear model (GLM) with random effects was performed and the beta estimates from each region were used to compare between groups. In the classification analysis a separate-subject GLM was performed and t-statistic maps were created for each subject which then were used as input to a logistic regression classifier.An interaction effect between group and butanol level was found in the right OFC (F(2.365;118.247)=3.032, p=0.043). Also, an interaction effect between group and butanol level emerged in the right PC (F(3,150)=4.537, p=0.004). Stimulus-evoked activation in both the left OFC and left PC did not show any significant effect. Planned contrast of the highest odor concentration minus the lowest odor concentration activation between groups revealed a significant difference in the right OFC (t(51)=2.339, p=0.023). The same contrast showed a significant difference between USH patients and controls in the right PC (t(51)=-3.380, p=0.001).As for the USH patients vs controls classification analysis we report a predictor model with accuracy of 71.7% (p=0.0072), sensitivity of 67.7% (p=0.0328), specificity of 77.3% (p=0.0041) and an AUC of 0.785 (p=0.0087).These data provide evidence of decreased activation in the right PC and increased compensatory activation in the right OFC in USH patients reinforcing the notion of dysfunctional olfactory sensory function. Also, it shows that olfactory fMRI patterns can discriminate USH patients from controls which holds promise in USH diagnosis improvement.
Silson, E. H., Declan J. McKeefry, J. Rodgers, A. D. Gouws, M. Hymers, and A. B. Morland. "Specialized and independent processing of orientation and shape in visual field maps LO1 and LO2." 2013. http://hdl.handle.net/10454/6191.
Повний текст джерела