Voxel-based morphometry
The voxel - based morphometry ( VBM ) is concerned with describing brain structures from tomographic imaging by size, intensity, shape and texture parameters quantitatively. These metrics are used in statistics and analyzed together with other clinical and experimental parameters.
The term voxel is made up of the words volumetric and pixel ( picture element ) together. A voxel is a three-dimensional equivalent of a pixel. The morphometry is to characterize the shape of objects by quantifiable values .
In order to analyze differences in the human brain, wherein the voxel -based morphometric the entire brain volume on the voxel level to levels of gray or white matter of the brain, or liquid / bone structure is checked. In this case, all MRI images of the examined brains are brought to a common level, to evaluate the data in a standard room. Thus comparisons between multiple people are possible. First, the orientation and size of the images of the brains to be corrected: the orientation in space is done by shift and rotation, and resizing by scaling and shearing. After that, all brain volumes are in the same standardized space, the local structural differences are highlighted. The subsequent division into portions resulting parametric maps with corresponding units for gray or white matter, and the cerebrospinal fluid / bone structures. The cards will be statistically analyzed at each voxel. Thus, the local structural differences can be calculated which have a different concentration or a different volume.