Rabu, 30 September 2009

Diffusion Tensor Imaging

Diffusion Tensor Imaging.Technique in whichat least six diffusion-weighted images with different gradient combinations must be acquired to permit the calculation of the diffusion tensor.Determination of the tensor permit the full realisation of the true 3-D nature of diffusion.It is rotationally in variant measurement i.e unlike ADC the values are not governed by the orientation of the structure in relation to the scanner.The tensor ,once computed can be displayed on an image as a diffusion ellipsoid.Alternatively,the dominant or preferred diffusion direction can be used to portray diffusion pathways.This is used in the brain to visualise white matter tracts and is called tractography.

Specially,the diffusion tensor is a symmetric 3 x 3 matrix.The eigenvalues relate to the diffusivities along three directions given by the eigenvectors.One eigenvalue represents diffusion along the preferred or primary direction while the second and third relate to perpendicular directions.

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