The "DH68" stereotactic atlas of baboon brain: definitions and reference data.

http://www.imaging.wustl.edu/PETPharm/dh68.htm

* Based on the following reference: Davis, R. and R. Huffman (1968). A Stereotaxic Atlas of the Brain of the Baboon. Austin, Texas, University of Texas Press.

* (At present) uses rotation to the same orientation as the above atlas, linear scaling based on landmark points visible in the MR image, and a single reference point (AC), to place MRIs in register with the standard atlas.

* Note: atlas (0,0,0) is an arbitrary point in cerebellum labelled as zero in the Davis and Huffman atlas. We compute this point by reference from the AC, which is fixed but does not have coordinates of zero.

* X is left-right, Y is anterior-posterior, and Z is superior-inferior.

* Right is positive. Anterior is positive. Superior is positive.

* All dimensions are given in mm.

* Atlas points are given as e.g. (1.2, 2.3, -4.8), which refers to 1.2mm to the right of midline, 2.3mm anterior to atlas zero, and 4.8mm inferior to atlas zero.

Definitions

* AC := center of anterior commissure, (0.0, 21.0, 7.0)

* PC := top edge of posterior commissure, (0.0, 6.5, 7.05)

(Note: these definitions deviate from those of the Talairach atlas so as to have 2 points at essentially the same Z coordinate; this simplifies things a little.)

Rotation

* The image is rotated so that

- the midsagittal plane is vertical (i.e. parallel to X = 0), and

- the AC and PC are at the same height (i.e. Z coordinate).

* After this rotation, sagittal, coronal and transverse refer to image planes in which X, Y or Z (respectively) are constant.

Scaling

* Anterior-posterior scaling factor (Y) is the AC-PC distance (in the atlas, this is 14.5mm)

* X and Z scaling factors are taken from measurements on the coronal plane passing through the AC:

- Left-right scaling factor (X) is the horizontal distance between the most medial points of the putamen on this plane (atlas: 19.5mm)

- Superior-inferior scaling factor (Z) is the average (L and R) vertical distance between the superior border of the caudate nuclei on this plane and the inferior border of the optic tracts on this plane (atlas: 23.2mm)

Translation

* Images are translated so that the AC is in a fixed location.

* We have taken the atlas as an image with:

- 128 x 128 pixels in the transverse plane and 64 contiguous transverse planes

- voxel size 1mm in each dimension

* Using ANALYZE conventions, the AC falls at image voxel (64.5, 85.5, 29.0); i.e. between the 64th and 65th pixels in a right -> left row, between the 85th and 86th pixels in a posterior -> anterior column, and centered on the 29th slice (inferior -> superior).

* This places atlas zero (0, 0, 0) at image voxel (64.5, 64.5, 22.0) using the same conventions.

* NOTE: this differs from the previously published image description because originally a 77-slice image was used, and now a 64-slice image is used. The two are top-aligned, but ANALYZE counts slices from the bottom. The above description is correct for the 64-slice images.