Hi,
I am trying to perform longitudinal registration using SPM12 （Serial Longitudinal Registration). According to the manual, “Prior to running the registration, the scans should already be in very rough alignment, although because the model incorporates a rigid-body transform, this need not be extremely precise.” However, I am unsure what steps I should take to achieve “rough alignment” of the scans within a subject. Does this mean I can linear register the anatomical images to a specific age (e.g., the image with the youngest age within a subject)?