JHA410H1 Lecture Notes - Lecture 4: Mri Sequence, Tractography, Voxel
Document Summary
Dti is a structural imaging technique that uses a specific mri sequence to characterize water diffusion within tissue to infer tissue structure. Gradient strength and diffusion time can modulate diffusion contrast: the longer the time the more diffusion information but the more the signal decays (i. e. less resolution) There are 4 main measures of water diffusion: axial diffusivity: increases with brain maturation and decreases with axonal injury, high ad = high fa = anisotropy. From tensor color you can infer direction. In general, dti allows us to characterize white matter pathways by two methods: tractography: location/direction, anistropy: integrity (or health) There are three main types of tracts in the cns (i. e. bundles of axons connecting regions of the brain categorized on their types of connections: commissural fibres: connect corresponding cortical regions in the two hemispheres. Long associations fibres: between lobes (e. g. inferior frontal-occipital fasciculus) Tractography paper: pre-surgical mapping for brain tumour resection.
