Glossary

This page tries to explain some may be uncommon terms related to this project.

Voxel and Cell

• Voxel - The center point of the volume region where the data was measured (averaged). Sometimes also the region itself. The positions in the grids are the voxels.
• Cell - In a 3D regular grid the volume enclosed by eight neigboring voxels forming a cube.

Partial Volume Effect

The partial volume effect occurs when a single voxel contains a mixture of multiple tissue values which may result in blurring or dimming parts. Other effects may be that tracked fibers are discontinous or broken.

Medical Abbreviations

For an overview on brain anatomy, you should have a look at http://www.healcentral.org/content/6831/Anatomy%20of%20Brain.ppt

| LCS, CSF | Liquor cerebrospinalis or Cerebrospinal fluid | | WM | White Matter | | GM | Gray Matter | | MRI | Magnetic Resonance Imaging | | dwMRI, dMRI | Diffussion weighted MRI | | DTI | Diffusion Tensor Imaging | | CNG,CG | WM Bundle - Cingulum | | CC | WM Bundle - Corpus Callosum | | FMaj | WM Bundle - Forceps Major | | FMin | WM Bundle - Forceps Minor | | CST | WM Bundle - Cortico Spinal Tract | | FA | Diffusion Index - Fractional Anisotropy | | GFA | Diffusion Index - Generalized Fractional Anisotropy | | LA | Diffusion Index - Linear Anisotropy | | RD | Diffusion Index - Radial Diffusivity | | MD | Diffusion Index - Mean Diffusivity | | ADC | Diffusion Index - Apparent Diffusion Coefficients |

Diffusion Tensor

A second order Diffusion Tensor in three dimensions is a essentially a 3x3 matrix attempting to model the diffusion process:

$$ \underline{D}=\left(\begin{smallmatrix}D_{xx} & D_{xy} & D_{xz}\\D_{yx} & D_{yy} & D_{yz}\\D_{zx} & D_{zy} & D_{zz}\end{smallmatrix}\right) $$

based on this matrix there are multiple diffusion indices defined. They may or may not exist also for higher order tensors (FA versus GFA). A symmetric tensor of order k and dimension d has {{latex(${d+k-1}\choose{k})}} different independent components. The following lists some numbers for d=3: