The QTI framework has been designed to improve discrimination of the sizes, shapes, and orientations of diffusion microenvironments within tissue.
For DTI, a DW-SE-EPI sequence was used with 30 orientations of diffusion gradients with b = 700 s mm−2 (+ b = 0 volume): TE = 72 ms, TR = 10 s (TR = 14 s for adults), parallel imaging GRAPPA factor 2, partial Fourier sampling factor 6/8, leading to an acquisition time of 5 min 40 s (7 min 56 s for adults).
Based on the determined diffusion tensor, the localized orientation of preferential diffusion and the localized diffusion anisotropy can be determined [ 33, 127, 130, 134].
In this article, we illustrate, primarily with examples from our own laboratory, how fast-scanning STM can be applied successfully to studies of dynamic processes on surfaces, in particular (a) mass transportation induced by adsorption, (b) diffusion of adatoms on surfaces, (c) diffusion of vacancies on TiO2, and (d) the influence of molecular orientation on diffusion properties.
It can then be used to derive mean diffusivity, diffusion anisotropy, and the dominant orientation of the diffusion process.
For the first time, a systematic investigation has been carried out on the pressure and orientation dependence of diffusion along grain boundaries.
A conceptual numerical model was built to study the effect of reduced fracture conductivity on oil recovery efficiency and the impact of system size and orientation on diffusion dominated oil recovery during CO2 injection in fractured systems.
MD from DTI takes into account the orientation of the diffusion ellipsoid in each voxel, while ADC from DWI represents diffusion in the orthogonal measurement directions as applied to every voxel.
While parametric methods directly describe the principal diffusion directions, interpreting the ODFs from model independent representations usually involves finding the number and orientation of principal diffusion directions present [39 41].
But as we are about to show in Section 2.2 it is possible to represent the orientation of the diffusion tensor with Euler angles.
