OBJECTIVE To calibrate and correct the gradient errors including gradient amplitude scaling errors, background/imaging gradients, and residual gradients in diffusion tensor imaging (DTI). METHODS A calibration protocol using an isotropic phantom was proposed. Gradient errors were estimated by using linear regression analyses on quadratic functions of diffusion gradients along 3 orthogonal dir...

Since the advent of magnetic resonance imaging (MRI) and computed tomography (CT) scanners around the early seventies, and the consequent ubiquitousness of medical volume data, medical visualization has undergone significant development and is now a primary branch of Visualization. It finds application in diagnosis, for example virtual colonoscopy, in treatment, for example surgical planning an...

The spherical tensor gradient operator Y l (∇), which is obtained by replacing the Cartesian components of r by the Cartesian components of ∇ in the regular solid harmonic Y l (r), is an irreducible spherical tensor of rank l. Accordingly, its application to a scalar function produces an irreducible spherical tensor of rank l. Thus, it is in principle sufficient to consider only multicenter int...

We investigated 2 Japanese siblings with a complicated form of familial spastic paraplegia. Cranial magnetic resonance (MR) imaging revealed marked thinning of the corpus callosum. Diffusion tensor imaging (DTI) showed microstructural changes in the thalamus, basal ganglia, and cerebral white matter, and single photon emission computed tomography (SPECT) using 99mTc-ethylcysteinate dimer showed...

We describe a collaborative virtual environment system for visualization of diffusion magnetic resonance imaging scans. The system represents the 3D data by arrays of polyhedra, coloured by the degree of anisotropy and directed by the principal component of the diffusion tensor. Users can then collaboratively explore the data and interactively spawn tractography procesess that compute tracks th...

Magnetohydrodynamic(MHD) peristaltic flow of a Couple Stress Fluid through a permeable channel is examined in this investigation. The flow analysis is performed in the presence of an External Magnetic Field. Long wavelength and low Reynolds number approach is implemented. Mathematical expressions of axial velocity, pressure gradient and volume flow rate are obtained. Pressure rise, frictional f...

OBJECTIVE To review state-of-the-art neuroimaging modalities in epilepsy and their clinical applications. DATA SOURCES AND STUDY SELECTION PubMed literature searches to March 2010, using the following key words: 'epilepsy', 'positron emission tomography (PET)', 'single photon emission computed tomography (SPECT)', 'MR volumetry', 'diffusion tensor imaging', and 'functional MR imaging'. DATA...

Second-order tensors may be described in terms of shape and orientation. Shape is quantified by tensor invariants, which are fixed with respect to coordinate system changes. This chapter describes an anatomically-motivated method of detecting edges in diffusion tensor fields based on the gradients of invariants. Three particular invariants (the mean, variance, and skewness of the tensor eigenva...

Trends in the chlorine chemical shift (CS) tensors of amino acid hydrochlorides are investigated in the context of new data obtained at 21.1 T and extensive quantum chemical calculations. The analysis of chlorine-35/37 NMR spectra of solid L-tryptophan hydrochloride obtained at two magnetic field strengths yields the chlorine electric field gradient (EFG) and CS tensors, and their relative orie...

A second order tensor is usually used to describe the diffusion of water for each voxel within a Diffusion Tensor Magnetic Resonance (DT-MR) images. However, a second order tensor approximation fails to accurately represent complex local tissue structures such as crossing fibers. Therefore, higher order tensors are used to represent more complex diffusivity profiles. In this work we examine and...