What is diffusion tensor in physics?
What is diffusion tensor in physics?
The tensor model is adopted to describe this diffusion anisotropy, and it allows one to quantify anisotropy parameters (related to white matter integrity) and to reconstruct the trajectory of white matter fibers (diffusion tractography). …
What does diffusion tensor imaging do?
Diffusion tensor imaging (DTI) is a promising method for characterizing microstructural changes or differences with neuropathology and treatment. The diffusion tensor may be used to characterize the magnitude, the degree of anisotropy, and the orientation of directional diffusion.
How is tractography done?
Tractography is performed using data from diffusion MRI. Bundles of axons provide a barrier to perpendicular diffusion and a path for parallel diffusion along the orientation of the fibers. Anisotropic diffusion is expected to be increased in areas of high mature axonal order.
How is DTI done?
In other words, the DTI technique involves the delivery of external magnetic pulses to impose a random phase shift for water molecules that diffuse. This leads to a loss of signal from diffusing molecules, which subsequently creates darker volumetric pixels or voxels.
Is DTI structural or functional?
Thus, DTI provides information about structural connectivity, as compared to functional connectivity data from rsFMRI. Perhaps most importantly, DTI can illustrate to the surgeon the relationship of a tumor to underlying white matter tracts.
How long does a DTI scan take?
The exam usually takes 1 to 2 hours. It is important that you relax and lie as still as possible. Any movement during this time will blur the picture. You may be given an injection of contrast dye into your arm or through an IV to enhance the images.
What is white matter tractography?
WHITE MATTER TRACTOGRAPHY (WMT) White Matter Tractography techniques estimate the connectivity patterns between different brain regions from the continuity in the local estimates of fiber direction at each voxel. To date, a large number of WMT algorithms have been proposed.
What is superscript T in the tensor model of diffusion?
Superscript T indicates the matrix transpose. The tensor model of diffusion consists of a 3 × 3 matrix derived from diffusivity measurements in at least six noncollinear directions.
Is diffusivity directionally dependent on fiber tract orientation?
Diffusion is anisotropic (directionally dependent) in WM fiber tracts, as axonal membranes and myelin sheaths present barriers to the motion of water molecules in directions not parallel to their own orientation. The direction of maximum diffusivity has been shown to coincide with the WM fiber tract orientation ( 9 ).
How do you map the direction of maximum diffusivity?
The direction of maximum diffusivity may be mapped by using red, green, and blue (RGB) color channels with color brightness modulated by FA, resulting in a convenient summary map from which the degree of anisotropy and the local fiber direction can be determined ( Fig 2) ( 16 ). Fig 2. A, FA map without directional information.
