The ICBM452 atlas is an average of T1-weighted MRIs of normal young adult brains. The space the atlas is in is not based on any single subject. Instead it is an average space constructed from the average position, orientation, scale, and shear from all the individual subjects. The atlas, therefore, is both an average of intensities and of spatial positioning.

### About the Atlas

##### Affine AIR 12 Atlas

The atlas was created using AIR5.0 and exists in two forms. The first is based on linear transforms of the subjects into the atlas space using a 12-parameter affine transformation (the air12 atlas). This atlas uses chirp-z interpolation for the voxel intensities. The second is based on a 5th order polynomial transformation into the atlas space (the warp5 atlas). The atlas was created using AIR5.0 and exists in two forms.

The first is based on linear transforms of the subjects into the atlas space using a 12-parameter affine transformation (the air12 atlas). This atlas uses chirp-z interpolation for the voxel intensities.

##### Warp 5 Atlas

The second atlas is based on a 5th order polynomial transformation into the atlas space (the warp5 atlas). This atlas uses a 3D-sinc interpolation with half-windows of 6 voxels in each dimension. It has a more accurate alignment then the linear atlas and shows more detail.