I have a (quite) simple question about SPM PET analyses.
I have been running simple regression between PET data and a covariate (let's say static amyloid PET images and a simple cognitive score performance) in a group of participants to investigate the possible relationship between the cerebral uptake and my variable of interest.
I used the multiple regression design, select my scans (normalised and smoothed) and enter my covariate vector (so far so good).
I am not quite sure of the optimal following parameters to enter in my model:
1- Global calculation: I used to put "omit", but that may be a mistake?
2- The "overall grand mean scaling" option for global normalisation: I don't really understand the point of such scaling, but maybe this would be important for me to use? any recommandations? and then should I add the normalisation option (proportional/AnCOVA)?
Thank you for your help on this. I really want to avoid silly mistakes.
And sorry if these questions have already been addressed, could you then indicate me to the corresponding answer?