> can somebody tell me if it within SPM is possible either to:
> for each individual subject segment one brain structure as for example the
> cerebellum and retrieve the mean signal intensity from the cerebellum as a
> whole and thereafter divide each voxel in all the images with that signal?
not as such but you can use the automatic segmentation and then either
remove the cerebellum by hand or using a mask if you want to work in the
> for each individual subject draw ROI's in the images containing a spesific
> brain structure as for example the cerebellum, and retrieve the mean
> signal intensity from the ROI's and thereafter divide each voxel in all
> the images with that signal?
drawing ROI has to be outside SPM using Analyze or MRIcro - then using
ImCalc simply multiply the segmented image by the ROI (i1.*i2) so you
get as output only this structure - be careful with the interpolation
method though .. (with trilinear I use to take the absolute values then
put to 0 values under 0.5) - For more calculations as you want to do it
is simple matlab stuffs. Say for instance
mean(mean(mean(image(ROI==1)))) given that image is the all brain and
ROI is a binary image of the cerebellum gray matter then you have the
mean for image only where ROI = 1, i.e. the mean signal of the
cerebellum. Nothing automatic (button press) here but rather
Hope this helps
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