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

Diffusion Tensor

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

\underline{D}=\left(\begin{matrix}D_{xx} & D_{xy} & D_{xz}\\D_{yx} & D_{yy} & D_{yz}\\D_{zx} & D_{zy} & D_{zz}\end{matrix}\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 {d+k-1}\choose{k} different independent components. The following lists some numbers for d=3: