Inconsistent X-Y location of labels for PAM50_label_body.nii.gz

[jcohenadad]

Context

From forum post: https://forum.spinalcordmri.org/t/registration-of-lumbar-data-to-pam50/1109

While working with the labels I saw that the PAM_label_body usually places the label at 70/70/xx but labels 15:18,20 are at 70/71/xx, so one voxel more anterior. Maybe this is intentional but it looked a bit unusual.

The reason for this inconsistency is likely because labels were created at the center of mass of the cord segmentation, which happens to be slightly shifted along the A-P direction depending on the S-I location.

Solution

We could re-generate all labels, making sure they are centered at x=70, y=70.

Pros:

• Easier to visualise
• Less confusing for users

Cons:

• Labels are not centered according to the center of mass anymore (ie: 70,70 is kind of 'arbitrary'). Although this is a minor cons.

Important
We should make sure that, if other PAM50 label files are also affected by this problem, we also fix them in the same PR.

[jcohenadad]

Alternatively, remove that file, see spinalcordtoolbox/spinalcordtoolbox#4229

Also related to #25