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Investigation of MS normal-appearing brain using diffusion tensor MRI with clinical correlations.

OBJECTIVE: To quantitatively investigate water diffusion changes in normal-appearing white matter (NAWM) and gray matter in patients with MS, and to evaluate whether these changes are correlated with clinical disability and disease duration. BACKGROUND: Diffusion tensor imaging provides quantitative information about the magnitude and directionality (anisotropy) of water diffusion in vivo and detects pathologic changes in MS brain tissue. METHODS: Diffusion tensor imaging was performed in 39 patients with MS and in 21 age-matched control subjects. Quantitative indices, including fractional a…

Microstructural injury to the optic nerve with vigabatrin treatment in West syndrome: A DTI study.

To evaluate optic nerve injury associated with vigabatrin treatment in children with West syndrome using diffusion tensor imaging. Thirty-five children with West syndrome (aged 9 days-22 months) were retrospectively analyzed and grouped as follows: (1) vigabatrin with symmetrical thalamic abnormalities, (2) vigabatrin without thalamic abnormalities, and (3) controls on other anti-seizure medications. Fractional anisotropy and apparent diffusion coefficient values of the optic nerves were assessed. ROC curves were used to determine fractional anisotropy thresholds for optic nerve injury. fracti…

Pre- and post-operative diffusion tensor imaging of the median nerve in carpal tunnel syndrome.

OBJECTIVES: To use pre- and post-operative diffusion tensor imaging (DTI) to monitor median nerve integrity in patients suffering from carpal tunnel syndrome (CTS). METHODS: Diffusivity and anisotropy images along the median nerve were compared among 12 patients, 12 age-matched and 12 young control subjects and correlated with electrophysiological neurography results. Slice-wise DTI parameter values were calculated to focus on local changes. RESULTS: Results of pre-operative patients and age-matched control subjects differed only in the distal nerve. Moreover, pre-operative patients differed…

Imaging diamagnetic susceptibility of collagen in hepatic fibrosis using susceptibility tensor imaging.

PURPOSE: To characterize the magnetic susceptibility changes of liver fibrosis using susceptibility tensor imaging. METHODS: Liver biopsy tissue samples of patients with liver fibrosis were obtained. Three-dimensional gradient-echo and diffusion-weighted images were acquired at 9.4 T. Susceptibility tensors of the samples were calculated using the gradient-echo phase signal acquired at 12 different orientations relative to the B0 field. Susceptibility anisotropy of the liver collagen fibers was quantified and compared with diffusion anisotropy, measured by DTI. For validation, a comparison wa…

The link between diffusion MRI and tumor heterogeneity: Mapping cell eccentricity and density by diffusional variance decomposition (DIVIDE).

The structural heterogeneity of tumor tissue can be probed by diffusion MRI (dMRI) in terms of the variance of apparent diffusivities within a voxel. However, the link between the diffusional variance and the tissue heterogeneity is not well-established. To investigate this link we test the hypothesis that diffusional variance, caused by microscopic anisotropy and isotropic heterogeneity, is associated with variable cell eccentricity and cell density in brain tumors. We performed dMRI using a novel encoding scheme for diffusional variance decomposition (DIVIDE) in 7 meningiomas and 8 gliomas p…

Quantitative diffusion tensor imaging analysis does not distinguish pediatric canines with mucopolysaccharidosis I from control canines.

Purpose We compared fractional anisotropy and radial diffusivity measurements between pediatric canines affected with mucopolysaccharidosis I and pediatric control canines. We hypothesized that lower fractional anisotropy and higher radial diffusivity values, consistent with dysmyelination, would be present in the mucopolysaccharidosis I cohort. Methods Six canine brains, three affected with mucopolysaccharidosis I and three unaffected, were euthanized at 7 weeks and imaged using a 7T small-animal magnetic resonance imaging system. Average fractional anisotropy and radial diffusivity values we…

Shear wave propagation in a prestressed and transversely isotropic viscoelastic material: Inverse modeling challenges and strategies.

The functional role and structure of some biological tissues, such as skeletal muscle, result in anisotropy in both material properties and imposed stresses. Dynamic elastography reconstruction methods for estimating soft tissue viscoelastic properties that are rooted in assumptions of isotropy in both the material properties and the imposed mechanical stress field may produce inaccurate estimates. The superposition of axially aligned orthotropy (transverse isotropy) and uniaxial prestress due to passive stretch or muscle activation makes it difficult to independently discern what part of the …

Observations of anisotropic paramagnetic and diamagnetic susceptibility in the primate brain.

Bulk magnetic susceptibility in the brain white matter is known to be diamagnetic and anisotropic due to the ordered myelin lipids. While paramagnetic iron is widely present in the brain, it is typically not considered to contribute to anisotropy. Using experimental MRI and computational techniques, this study explores the competing contribution of diamagnetic and paramagnetic substances to the susceptibility anisotropy. Multi-echo gradient-echo imaging and diffusion-weighted imaging data from a paraformaldehyde-fixed post-mortem chimpanzee (Pan troglodytes verus) brain was analyzed. A computa…

Distinct ferrovalley characteristics of the Janus RuClX (X = F, Br) monolayer.

Two-dimensional ferrovalley materials should simultaneously possess three characteristics, that is, a Curie temperature beyond atmospheric temperature, perpendicular magnetic anisotropy, and large valley polarization for potential commercial applications. In this report, we predict two ferrovalley Janus RuClX (X = F, Br) monolayers by first-principles calculations and Monte Carlo simulations. The RuClF monolayer exhibited a valley-splitting energy as large as 194 meV, perpendicular magnetic anisotropy energy of 187 μeV per f.u., and Curie temperature of 320 K. Thus, spontaneous valley polariza…

Determinants of anisotropic water diffusion in nerves.

We report NMR diffusion measurements of water in three central nervous system models, namely the nonmyelinated olfactory, and the myelinated trigeminal and optic nerves of the spotted and long-nosed garfish. A similar degree of anisotropy of the average diffusion coefficients (DNMR) is observed for all three freshly excised nerve types (DNMR(parallel)/DNMR-(perpendicular) is 3.6 +/- 1.2, 3.2 +/- 0.9, and 2.6 +/- 0.4 for the olfactory, trigeminal, and optic nerves, respectively). The anisotropy of DNMR for the nonmyelinated olfactory nerve argues strongly that myelin is not a necessary determin…

Effect of atomic anti-site disorder on the anisotropic magnetoresistance in Fe50Co50alloys.

In order to understand the anti-site disorder effect on the anisotropic magnetoresistance (AMR) of alloys,Fe50Co50alloys were studied in this work using the fully relativistic spin-polarized Korringa-Kohn-Rostoker method. The anti-site disorder was modeled by interchanging Fe and Co atoms and treated by the coherent potential approximation. It is found that the anti-site disorder broadens the spectral function and decreases the conductivity. Our work emphasizes that the absolute variations of resistivity under magnetic moment rotation are less affected by atomic disorder. The annealing procedu

Liquid crystal cells with built-in CdSe nanotubes for chromogenic smart emission devices.

A simple and general approach for controlling optical anisotropy of nanostructured semiconductors is reported. Our design involves the fabrication of liquid crystal devices with built-in semiconductor nanotubes. Quite interestingly, it is found that semiconductor nanotubes can be well aligned along the orientation of liquid crystals molecules automatically, resulting in a very large emission anisotropy with the degree of polarization up to 72%. This intriguing result manifests a way to obtain well aligned semiconductor nanotubes and the emission anisotropy can be easily manipulated by an exter…

Alexithymia mediates white-matter microstructure and substance use escalation in trauma-exposed individuals.

INTRODUCTION: Alexithymia has been separately associated with differences in white-matter and with substance use (SU). Childhood trauma has … ater. Diffusion-weighted white-matter data were used to calculate tensor-derived and crossing-fiber anisotropy measures. Multivariable analyses and moderated mediation models tested whether the indirect relationship between corpus callosum anisotropy and SU escalation through alexithymia differed between levels of childhood trauma. RESULTS: Splenium primary …

White Matter Microstructural Alterations in Newly Diagnosed Parkinson's Disease: A Whole-Brain Analysis Using dMRI.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by cardinal motor symptoms and other non-motor symptoms. Studies have investigated various brain areas in PD by detecting white matter alterations using diffusion magnetic resonance imaging processing techniques, which can produce diffusion metrics such as fractional anisotropy and quantitative anisotropy. In this study, we compared the quantitative anisotropy of whole brain regions throughout the subcortical and cortical areas between newly diagnosed PD patients and healthy controls. Additionally, we evaluated the correlat…

Diffusion tensor imaging and diffusion-weighted imaging on axillary lymph node status in breast cancer patients.

PURPOSE This article will examine the usefulness of diffusion tensor imaging (DTI) and diffusion-weighted imaging (DWI) on the assessment of axillary lymph nodes (ALN) of breast cancer patients. METHODS Axillary lymph nodes in 66 breast cancer patients were examined by DTI and DWI, and the largest lymph node with increased cortical thickness in axilla was selected. Morphological features, apparent diffusion coefficient (ADC), volume anisotropy, and fractional anisotropy values were measured by using a special software. Imaging findings and histopathological results were recorded. RESULTS Metas…

Covariant stringlike dynamics of scroll wave filaments in anisotropic cardiac tissue.

It has been hypothesized that stationary scroll wave filaments in cardiac tissue describe a geodesic in a curved space whose metric is the inverse diffusion tensor. Several numerical studies support this hypothesis, but no analytical proof has been provided yet for general anisotropy. In this Letter, we derive dynamic equations for the filament in the case of general anisotropy. These equations are covariant under general spatial coordinate transformations and describe the motion of a stringlike object in a curved space whose metric tensor is the inverse diffusion tensor. Therefore the behavio…

The role of corticospinal and extrapyramidal pathways in motor impairment after stroke.

Anisotropy of descending motor pathways has repeatedly been linked to the severity of motor impairment following stroke-related damage to the corticospinal tract. Despite promising findings consistently tying anisotropy of the ipsilesional corticospinal tract to motor outcome, anisotropy is not yet utilized as a biomarker for motor recovery in clinical practice as several methodological constraints hinder a conclusive understanding of degenerative processes in the ipsilesional corticospinal tract and compensatory roles of other descending motor pathways. These constraints include estimating an…

The role of diffusion tensor imaging in the evaluation of ischemic brain injury - a review.

Water diffusion in brain tissue is affected by the presence of barriers to translational motion such as cell membranes and myelin fibers. The measured water apparent diffusion coefficient (ADC) value is therefore frequently anisotropic and varies depending upon the orientation of restricting barriers (such as white matter tracts) relative to the diffusion-sensitive-gradient direction. Anisotropic water diffusion can be specified using indices of diffusion anisotropy [e.g. standard deviation of the individual ADC values, fractional anisotropy (FA), lattice index (LI)], which are derived from me…

Тенсорная диффузия МРТ и NODDI в классификации множественных склерозов.

СПРАВОЧНАЯ ИНФОРМАЦИЯ: Многокамерные модели диффузии и многокамерные приобретения все чаще используются для преодоления ограничений, связанных с обычной диффузионной тенсорной съемкой, но требуют более длительных сканирования и более сложной обработки. В то же время исследования по диффузионной классификации МРТ часто основываются на узком наборе тенсорных метрик, особенно на фракционной анизотропии. Мы изучили вопрос о том, может ли более широкое использование настольных элементов, включая дескрипторы формы, улучшить классификацию без повышения сложности приобретения.МЕТОДЫ: МРИ с несколькими

Совпадение в аннотации оригинала
BACKGROUND: Multi-compartment diffusion models and multi-shell acquisitions are increasingly used to overcome limitations of conventional diffusion tensor imaging, but require longer scans and more complex processing. Meanwhile, diffusion MRI classification studies often rely on a narrow set of tensor-derived metrics, especially fractional anisotropy. We inv…

Presence of Auditory Pathway Abnormalities in Children With Neurofibromatosis Type 1 With Brainstem Focal Areas of Abnormal Signal Intensity: Diffusion Tensor Imaging Features.

Background: To investigate whether there is a difference in mean diffusivity (MD) and fractional anisotropy (FA) values in the auditory pathways of neurofibromatosis type 1 patients with and without focal areas of abnormal signal intensity (FASI) compared to healthy controls by using diffusion tensor imaging (DTI). Methods: Patients were classified as group 1 with focal areas of abnormal signal intensity in the brainstem, group 2 without focal areas of abnormal signal intensity, and healthy control group 3 according to the MRI findings. Mean diffusivity and fractional anisotropy values of late…