Dear Valeria,


Please see Yakushev I et al. Neuroimage 2009 for a detailed description of the process - as well as a better normalisation method than cerebellum :-).

All the best and hope this helps,

Alexander

-----------------------------------------
Alexander Hammers, MD PhD

Professor (Honorary Consultant) of Imaging and Neuroscience
Head of PET Imaging Centre
Division of Imaging Sciences and Biomedical Engineering
King's College London
St Thomas' Hospital, London

Telephone +44-(0)20 7188 8364 (PA Viviane Schroeder)
Email [log in to unmask]



On 09 Jun 2015, at 13:57, Valeria Isella <[log in to unmask]> wrote:

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