The reading network is only partially understood and even less is known regarding how the network functions when reading is impaired. Dyslexia is characterized by poor phonological processing and affects roughly 5-12% of the population. The Dorsal-Ventral and Cerebellar-Deficit models propose distinct behavioral and structural differences in young adults with dyslexia. Behavioral assessments were used to determine if deficits for young adults with dyslexia were restricted to the literacy domain or dispersed among reading and associated behavioral domains. Diffusion tensor imaging (DTI) was used determine the extent to which white matter pathways and gray matter regions differ structurally in young adults with dyslexia. The present study also investigated whether brain-behavior relationships exist and are consistent with the theoretical models of reading in this population. Findings show that young adults with dyslexia exhibited deficits in both literacy and associated behavioral domains, including verbal working memory and motor function. Structural findings showed increased fractional anisotropy in the left anterior region (the aslant) and decreased fractional anisotropy in left posterior regions (inferior occipital fasciculus and vertical occipital fasciculus) of the reading network for young adults with dyslexia. Brain-behavior associations were found between the right inferior frontal gyrus and decoding for those with dyslexia. These findings provide support for the use of an altered reading network by young adults with dyslexia, as outlined by the Dorsal-Ventral model of reading. Limited structural and behavior findings support of the Cerebellar-Deficit model of reading, findings that warrant additional investigation.

No description available.

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

Thesis (M.Sc (Radiography))--Cape Peninsula University of Technology, 2016. / Multiple sclerosis (MS) affects the central nervous system (CNS) and is characterized by multiple demyelinating lesions. It is in this context that a need arises for reliable biomarkers such as Magnetic Resonance Imaging (MRI), which could lead to the early diagnosis and therapeutic intervention when maximum potential impact is possible. This study examines the impact of MRI as a marker and the sequences that give the best images to aid in evaluation of disease progression (which can indirectly be seen as disability) and the early diagnosis of MS which will, in turn, lead to more effective management of the disease. METHOD: Sixteen subjects underwent a neurological examination, the Expanded Disability Status Scale (EDSS), blood tests for iron parameters and a 3Tesla Magnetic Resonance Imaging (MRI) scan. In a study of MS, 11 had MRI data that could be analysed by using tract-based spatial statistics (TBSS). Subjects were divided according to the EDSS score (8 of the subjects had an EDSS score of ≤ 3 while 3 subjects had scores of ≥ 6). Diffusion tensor imaging (DTI), the fused Proton Density and Fluid Attenuation Recovery (FLAIR) was utilised to compute the lesion numbers and standard laboratory procedures were used to measure other biochemical markers (serum iron, % transferrin saturation, ferritin, haemoglobin) in subjects with disability and simultaneously assess the disease process. RESULTS: The FA of white matter tracts (WMTs) as a parameter of myelin integrity was lower in subjects with MS only in those who had high EDSS scores. An association between FA and iron parameters, especially percentage transferrin saturation (% Tf) sat were observed, which suggests that iron availability to the WM may be a requirement for optimal myelin functionality. CONCLUSION: The FA of WMTs as a parameter of myelin integrity was lower only in those MS subjects who had high EDSS scores. Subjects who had EDSS scores < 3 (i.e. who had a “benign” disease outcome) had FA values similar to control values and this finding was not related to their age or disease duration. The association found between FA and iron parameters, especially % Tf sat, suggests that iron availability to the WM may be a requirement for optimal myelin functionality. Results also suggest that serum iron concentration, ferritin and % Tf sat had an effect on myelination. The lack of association between FA and Hb suggests that the iron in this protein is not available for WM function.

abstract: The objective of this small animal pre-clinical research project was to study quantitatively the long-term micro- and macro- structural brain changes employing multiparametric MRI (Magnetic Resonance Imaging) techniques. Two separate projects make up the basis of this thesis. The first part focuses on obtaining prognostic information at early stages in the case of Traumatic Brain Injury (TBI) in rat animal model using imaging data acquired at 24-hours and 7-days post injury. The obtained parametric T2 and diffusion values from DTI (Diffusion Tensor Imaging) showed significant deviations in the signal intensities from the control and were potentially useful as an early indicator of the severity of post-traumatic injury damage. DTI was especially critical in distinguishing between the cytotoxic and vasogenic edema and in identification of injury regions resolving to normal control values by day-7. These results indicate the potential of quantitative MRI as a clinical marker in predicting prognosis following TBI. The second part of this thesis focuses on studying the effect of novel therapeutic strategies employing dendritic cell (DC) based vaccinations in mice glioma model. The treatment cohorts included comparing a single dose of Azacytidine drug vs. mice getting three doses of drug per week. Another cohort was used as an untreated control group. The MRI results did not show any significant changes in between the two treated cohorts with no reduction in tumor volumes compared to the control group. The future studies would be focused on issues regarding the optimal dose for the application of DC vaccine. Together, the quantitative MRI plays an important role in the prognosis and diagnosis of the above mentioned pathologies, providing essential information about the anatomical location, micro-structural tissue environment, lesion volume and treatment response. / Dissertation/Thesis / Masters Thesis Bioengineering 2014

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19270号 / 医博第4034号 / 新制||医||1011(附属図書館) / 32272 / 京都大学大学院医学研究科医学専攻 / (主査)教授 髙橋 良輔, 教授 渡邉 大, 教授 富樫 かおり / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Introduction: Somatosensory evoked potentials (SSEP) play a pivotal role in the diagnosis and disease monitoring of multiple sclerosis (MS). Delayed latencies are a surrogate for demyelination along the sensory aerence. This study aimed to evaluate if SSEP latencies are representative of demyelination of the brain overall, by correlating with cerebral microstructural integrity as measured by Magnetic resonance (MR) diusion tensor imaging (DTI). Analysis was performed in a hypothesis-free whole brain approach using tract-based spatial statistics (TBSS). Material and methods: A total of 46 patients with MS or clinically isolated syndrome were included in the study. Bilateral SSEPs of the median nerve measuring mean N20 latencies (mN20) and Central Conduction Time (CCT), were acquired. MRI scans were performed at 3T. DTI acquisition was done with a single-shot echoplanar imaging technique with 80 diusion directions. The FSL software package was used to process the DTI datasets and to calculate maps of fractional anisotropy (FA), axial diusivity (AD), and radial diusivity (RD). These maps were then further analyzed using the TBSS module. The mean N20 and CCT and the right- and left-sided N20 and CCT were separately correlated to FA, AD, and RD, controlled for age, gender, and EDSS as variables of non-interest. Results: Widespread negative correlations of SSEP latencies with FA (p = 0.0005) and positive correlations with RD (p = 0.0003) were measured in distinct white matter tracts, especially the optic tracts, corpus callosum, and posterior corona radiata. No correlation with AD was found in any white matter tract. Conclusion: Highly significant correlations of FA and RD to SSEPs suggest that their latency is representative of widespread microstructural change, and especially demyelination in patients suering from MS, reaching beyond the classic somatosensory regions. This points to the usefulness of SSEPs as a non-invasive tool in the evaluation of microstructural damage to the brain.

No description available.

<p>Diffusion tensor (DT) and blood oxygen-level dependent (BOLD) imaging are two noninvasive magnetic resonance (MR) techniques that have been used to probe skeletal muscle microstructure and microvasculature, respectively. Over a series of four studies, the work in this thesis aimed at furthering our understanding of baseline DT metrics and BOLD signals in lower limb muscles (calf and foot) of healthy young subjects. Since postural changes have been shown to alter numerous quantities, including fluid volumes and muscle cross sectional area, DT indices and BOLD signal characteristics were examined in response to movement from upright to supine position.</p> <p>Reductions of 3.2-6.7% and 3.4-7.5% were measured in calf DT eigenvalues and apparent diffusion coefficient (ADC) in the various muscles, following 34 and 64 minutes of supine rest, respectively (P</p> <p>Establishment of baseline diffusion metrics in the foot region was feasible (chapter 6). Examination of foot DT indices in response to positional change showed that the metrics decreased from 2.7-4.6% following 34 minutes of supine rest (P</p> / Doctor of Philosophy (PhD)

Οι τεχνικές απεικόνισης μοριακής διάχυσης (DWI) και τανυστή διάχυσης (DTI) είναι από τις πιο δημοφιλείς τεχνικές μαγνητικής τομογραφίας (MRI) στην έρευνα του εγκεφάλου. Διάχυση (ή θερμική κίνηση Brown) είναι ένα τυχαίο φαινόμενο το οποίο περιγράφει τη μεταφορά υλικού (π.χ μόρια νερού) από μία χωρική θέση σε άλλη με την πάροδο του χρόνου. Η διάχυση του νερού σε βιολογικούς ιστούς παρατηρείται μέσα, έξω, γύρω από τις κυτταρικές δομές και είναι αποτέλεσμα της θερμικής ενέργειας των μορίων. Η κάθε τεχνική υποστηρίζεται από τον δικό της αλγόριθμο από τους οποίους προκύπτουν και οι αντίστοιχοι παραμετρικοί χάρτες. Πιο συγκεκριμένα από την τεχνική διάχυσης προκύπτει ο δείκτης της φαινόμενης σταθεράς διάχυσης (ADC-Apparent Diffusion Coefficient) , ενώ από την τεχνική του τανυστή διάχυσης προκύπτει ο δείκτης της κλασματικής ανισοτροπίας (FA-Fractional Anisotropy). Η παράμετρος ADC δείχνει πόσο διαφέρει η διάχυση στην περιοχή ενδιαφέροντος σε σχέση με την μέση τιμή διάχυσης. Η κλασματική ανισοτροπία (FA) είναι δείκτης μέτρησης του βαθμού ανισοτροπίας της διάχυσης και η τιμή της εξαρτάται άμεσα από την ακεραιότητα των νευρικών ινών. Το φάσμα εφαρμογής των δύο τεχνικών είναι ευρύ (εφαρμογή σε απομυελινωτικές νόσους, ισχαιμικά επεισόδια, εγκεφαλικοί όγκοι). Ο κύριος λόγος είναι ότι η διάχυση των μορίων νερού είναι ιδιαίτερα ευαίσθητη σε τυχόν αλλοιώσεις στη δομή των ινών της Λευκής ουσίας. Σκοπός της παρούσας ερευνητικής είναι η εφαρμογή των τεχνικών Τανυστή Διάχυσης (DTI) και Μοριακής Διάχυσης (DWI) σε τρείς κατηγορίες εγκεφαλικών όγκων (μηνιγγιώματα, γλοιώματα υψηλής και χαμηλής κακοήθειας, εγκεφαλικούς μεταστατικούς όγκους) με σκοπό τον διαχωρισμό αυτών. / The brain is a highly organized organ with a complex microstructural organization . The microstructural organization of brain tissue affects the molecular motion (diffusion) of water. Diffusion therefore reflects the structural organization of tissue. Diffusion imaging is a Magnetic Resonance (MR) imaging technique that allows the quantification to the molecular motion of water. Magnitude and directionality (anisotropy) of molecular motion of water can be described. Measurements of the magnitude of diffusion have been used to identify abnormal tissue in tumors, stroke, multiple sclerosis and status epilepticus. Diffusion tensor imaging (DTI) is a relatively new technique that allows rotationally invariant measurements of both magnitude and directionality of water diffusion. DTI sequences with calculation of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) scalars allow characterization of the shape and magnitude of the diffusion ellipsoid. These parameters consequently reflect the microstructural architecture of the human brain. In addition, quantification of diffusion can be especially helpful as it may allow early diagnosis of pathology . The purpose of this study was to correlate the changes in FA and ADC between three different brain tumors and outline the probability of presurgical tumor differentiation.