Dear Chiara,
> Hi, thank you for your reply and for your suggestion, I will invert
> registration and segmentation.
> Do you have any suggestion on modulation?
in general the recommendation is to modulate. The reason is as
follows: Let us say you have two subjects, one with a larger amygdala
and one with a smaller. Let us further say that the segmentation is
perfect, i.e. all the grey matter of the amygdala has been correctly
identified in both subjects. The registration will now shrink the big
amygdala and enlarge the small one so that they both match that the
template that is used. If we also assume the registration is perfect
this means the two images, and hence also the registered grey matter
segments, are now identical and if we try to look for difference s we
will not find any.
What the modulation does is to keep track of individual shrinkage and
enlargements so that the amygdala that was shrunk will be multiplied
by a number >1 and the amygdala that was enlarged will be multiplied
by a number <1 to reflect this. Slightly simplified one can say the
modulated values reflect "cc of gray matter per cc in standard space"
Hope that makes sense.
Jesper
|