Hi,
in Brian's thesis it says (page 177-178):
"In neuroanatomy, variation in the global scale of a structure may be
of interest as it may correspond to variations in grey matter volume
due to pathology. Thus strictly speaking we are usually interested in
investigating the variation in size-and-shape of the deep grey
structures.."
on the FIRST website:
http://www.fmrib.ox.ac.uk/fsl/first/index.html
it says:
"--useScale : Used in conjunction
with --useRigidAlign, it will remove global scalings when aligning
meshes."
"Also note that
the --useScale option will not be used. Without
the --useScale option, changes in both local shape and
size can be found in shape analysis. This type of finding can be
interpreted, for example, as local atrophy. With
the --useScale option, overall changes in size are lost."
i'm not sure i understand. No --useScale means that my metric does not separate size from shape, i.e. it is a size-and-shape analysis. i do not see how my finding can then be interpreted as local atrophy (size).
including --useScale or some kind of size variable in my statistical model assures, at least, that my metric is interpretable as shape, i.e. it is a shape analysis.
-joost