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Dear all,
I have several question regarding the affiliated Longitudinal batch in VBM8 toolbox.
As you see, the default in the "Writing options GM WM and CSF Modulated Normalized" option was set to none, which I assume would generate unmodulated images (In previous chapters of the VBM manual, Dr Glaser actually suggested using non-linear only). So is the default setting changed under the circumstance of Longitudinal Study? If so, why?
More importantly, in the third realignment the GM images are realigned to the group mean GM image (p1 I assume). But in the subsequent Apply Deformation module the deformation field is applied to both GM and WM images (p1 and p2). Are is GM the only matter of interest in this batch? If so, why apply the deformation field to the WM as well? If not, why not include WM images (p2) in the third realignment step?
Also, in the Apply Deformation Module, there is an option Modulate image(preserve volume) whose default was set to no. So I am a little bit confused here. If I am interested in the modulated images (i.e. preserving absolute volume), should I simultaneously set this to yes and set "Writing options GM WM and CSF Modulated Normalized" option in the VBM8: Est&Write Module to non-linear only?
Finally, I noticed that the smoothing part is missing in this batch. Does it mean that we don't need to smooth the normalised images?
Sorry about the amaturity of these questions, but I am new to structural image processing and I would really appreciate some insights.
Many thanks and best regards,
Ce