If a subject is imaged using different imaging modalities and protocols, during follow-up studies or if different animals are used, the subject is positioned in different ways and postural variations occur
In biomedical imaging research, anatomical atlases have pro- ven to be useful for defining a standard geometric reference for further subject analysis and meaningful comparisons.
Atlases may consist of a 3D, sometimes 4D, whole-body or organ-based geometric representations. This enables map- ping functional activity and anatomical variability among individuals and populations.
For example, it is possible to make population brain studies in a specific time frame. For that, brain images from each individual, obtained through MRI, PET, and other imaging techniques, are spatially warped to a brain template.
The atlas consists of a standard 3D coordinate space with labeled regions and structural probability maps and is available for clinical use. This