What is diffusion tensor imaging?

What is diffusion tensor imaging?

Diffusion tensor imaging allows measuring fractional anisotropy and similar microstructural indices of brain white matter, in which lower than normal fractional anisotropy is associated with loss of microstructural integrity and degeneration.

What is the apparent diffusion coefficient (ADC) for biological tissues?

Biological tissues are highly anisotropic, meaning that their diffusion rates are not the same in every direction. For routine DW imaging we often ignore this complexity and reduce diffusion to a single average value, the apparent diffusion coefficient (ADC), but this is overly simplistic.

How do you model diffusion in complex materials?

A superior method to model diffusion in complex materials is to use the diffusion tensor, a [3 x 3] array of numbers corresponding to diffusion rates in each combination of directions. The three diagonal elements ( D xx, D yy, D zz) represent diffusion coefficients measured along each of the principal ( x-, y- and z -) laboratory axes.

How do you measure the tensor elements in an MRI?

To measure these individual tensor elements we typically begin in the so-called laboratory ( x-y-z) frame, which for clinical MRI is typically aligned with the patient’s body and main magnetic field. Gradients are applied in different directions and several sets of raw data (source) images are obtained.

What is diffdiffusion imaging and how does it work?

Diffusion imaging is an MRI method that produces in vivo magnetic resonance images of biological tissues sensitized with the local characteristics of molecular diffusion, generally water (but other moieties can also be investigated using MR spectroscopic approaches). MRI can be made sensitive to the motion of molecules.

What type of diffusivity is used in dtdti?

DTI uses mean diffusivity for the rate of molecular diffusion, FA for the summative direction of the diffusion which provides a prominent vector, axial diffusivity for the rate of diffusion parallel to the main vector, and radial diffusivity for the rate of diffusion perpendicular to the main vector.

What is the diffusion model in image processing?

The diffusion model is a rather simple model of the diffusion process, assuming homogeneity and linearity of the diffusion within each image voxel. From the diffusion tensor, diffusion anisotropy measures such as the fractional anisotropy (FA), can be computed.