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hi everybody I am an absolute beginner with SPM I am trying to analyse FDG-PET brain images in patients with dementia using SPM8 I need to normalize scans intensity to the cerebellum, whose mean count values I have extracted with Marsbar how should I do that exactly..? my guess is I should use the 'user' option in Global calculation and input individual cerebellar means, and then select 'proportional scaling' in Global normalisation, but am I correct? or am I normalizing twice (i.e. to the cerebellum and to mean voxel value of the entire brain) if I select 'proportional scaling'? but if I choose 'none' in Global normalisation, then what does SPM do with the cerebellar values inputted in the user's vector..? hope that's clear enough many thanks Valeria