Ashburner John (PSYCHOLOGY) wrote:
> The Q-form is a bit limited. In SPM, I usually set it to be as close as
> possible to the S-form, and usually only the S-form is used by
> spm_get_space. Anyone who has worked with CT data will notice that
> shears would be desirable for representing the voxel-to-world mappings.
> Many CT images are skewed.
Ah, so then Ged's point (what's the use of the Q-form in the 1st place)
is a very good one.
There are no specifications as to what the Q-form and S-form should be
used for, respectively. But was there a rationale for having 2 separate
forms and making 1 more limited?
Things that I would think it could be handy for would be: coronal or
saggital slices instead of axial. Those positionings are rigid-body
transformations, and by using the Q-form for those, you keep your S-form
free for more demanding alignments.
best
Alle Meije
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