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To characterize anisotropic water diffusion in brain white matter, a theoretical framework is proposed that combines hindered and restricted models of water diffusion (CHARMED) and an experimental methodology that embodies features of diffusion tensor and q-space MRI. This model contains a hindered extra-axonal compartment, whose diffusion properties are(More)
Introduction White matter is composed of ordered fascicles whose axons are surrounded by a complex extra-axonal environment containing astrocytes, glia and extracellular matrix. It is suggested that the diffusion weighted (DW) signal at low and high b values may probe different water pools. Recently, a model of water diffusion in white matter was proposed(More)
Knowledge of microstructural features of nerve fascicles, such as their axon diameter, is crucial for understanding normal function in the central and peripheral nervous systems as well as assessing changes due to pathologies. In this study double-pulsed field gradient (d-PFG) filtered MRI was used to map the average axon diameter (AAD) in porcine spinal(More)
Introduction High b value diffusion weighted imaging (DWI) combined with q-space analysis enables one to measure dimensions of some cellular compartments (1-2). More recently q-space methods were combined with diffusion tensor imaging (DTI) in a composite hindered and restricted model of diffusion (CHARMED) MRI framework from which several microstructural(More)
Introduction: The diameter of myelinated axons is a crucial neurophysiological parameter that is linearly related to conduction velocity. In the spinal cord, axons are somatotopically organized into nerve bundles that perform specific functions and are characterized by different diameters and diameter distributions. The purpose of this study is to evaluate(More)
A double Pulsed Gradient Spin Echo (d-PGSE) MR experiment was used to measure and assess the degree of local diffusion anisotropy in brain gray matter, and in a novel "gray matter" phantom that consists of randomly oriented tubes filled with water. In both samples, isotropic diffusion was observed at a macroscopic scale while anisotropic diffusion was(More)
A double-pulsed gradient spin echo (d-PGSE) filtered MRI sequence is proposed to detect microscopic diffusion anisotropy in heterogeneous specimen. The technique was developed, in particular, to characterize local microscopic anisotropy in specimens that are macroscopically isotropic, such as gray matter. In such samples, diffusion tensor MRI (DTI) produces(More)
One aim of this work is to investigate the feasibility of using a hierarchy of models to describe diffusion tensor magnetic resonance (MR) data in fixed tissue. Parsimonious model selection criteria are used to choose among different models of diffusion within tissue. Using this information, we assess whether we can perform simultaneous tissue segmentation(More)
In this work we investigate the feasibility and effectiveness of unsupervised tissue clustering and classification algorithms for DTI data. Tissue clustering and classification are among the most challenging tasks in DT image analysis. While clus­ tering separates acquired data into objects, tissue classifica­ tion provides in-depth information about each(More)
Quantitative assessment of perfusion defects with myocardial contrast echocardiography can be a valuable tool in the evaluation of patients with coronary artery disease. However, the use of 2-dimensional echocardiography for this purpose is limited to a restricted number of imaging planes. Real-time 3-dimensional echocardiography (RT3D) is a novel technique(More)