► MSA of cylindrically symmetric matter is estimated from n(≥3) orientations and DTI. The layering and the regional foliation are subhorizontal to shallowly dipping to the NE. This study is the first detailed investigation of magnetic fabrics in migmatites. The magnetic anisotropy of rocks is often determined by means of the analysis, of the anisotropy of the magnetic susceptibility (AMS), which is the significant property that has found the most geophysical applications.
The magnetic susceptibilities are generally high, around (5-10) × 10-3 SI.
For magnetite, AMS primarily defines grain-shape anisotropy; for other minerals, AMS expresses crystallographic control on magnetic properties. In addition to the long scan time to acquire a single orientation (~10 min in this study without parallel imaging), repositioning and stably holding a human head at various orientations required particular care and time in preparing for each of the scans. MSA from the STI reconstruction is always positive due to the ordering of the eigenvalues and there is no natural way to define parallel and perpendicular components explicitly in this reconstruction. Third column: the absolute value of the dot product between the vectors.The coefficients of these square block matrices can be easily calculated to evaluate the eigenvalues and condition of this system.Cylindrically symmetric susceptibility tensor estimation guided by DTI from human feasible three orientations (3CSST)a, Eigenvalues of the STI and parallel and perpendicular components of the CSST reconstructions of the phantom consisting of both isotropic and anisotropic materials. The black triangle and square indicate the location of the mean anisotropy detected in the 12-CSST and 12-STI reconstructions respectively.Mean AMS detected across reconstructions of 12 orientations in Subject 1, in ppbWhite matter is an essential component of the central nervous system and is of major concern in neurodegenerative diseases such as multiple sclerosis (MS). The anisotropies generated from these reconstructions were evaluated against the known anisotropy in the simulation. Magnetic properties are carried mainly by multidomain (MD) primary magnetite grains ranging in size from 20 to 200 μm. MSA of cylindrically symmetric matter is estimated from n(≥3) orientations and DTI. Recent MRI studies have explored the unique anisotropic magnetic properties of white matter using susceptibility tensor imaging. Mineralogical changes resulting from heating samples in the laboratory …
We find that DTI guided estimation of cylindrical MSA in major white matter tracts of the brain can be reasonable with as few as three non-coplanar orientations particularly in the corpus callosum and optic radiations.The sensitivity of the anisotropy estimation to various acquisition orientations was investigated in this simulated data set. From this we can obtain one expression for a cylindrically symmetric susceptibility tensor:MSA maps generated from the 3-CSST of all of the volunteers, view in sagittal (top), axial (middle) and coronal (bottom) section.Comparison of MSA maps generated within Subject 1 compared to the color FA generated from the diffusion data.Analysis of susceptibility anisotropy error sensitivity to fiber directions and sampling orientation distributionMean AMS detected across 3-CSST reconstructions of all volunteers, in ppbFirst and second columns: maps of the principal eigenvector direction as derived from DTI and STI (both weighted by the FA from DTI) in sagittal (top), axial (middle) and coronal (bottom) section.