Dear Silvana,
The question is not simple. So, you actually have CMRGlu acquired using dynamic PET scans?
Basically, the scaling that you want to apply depends on which is your research question. If you want to study how the anaesthetics affect the global methabolism then you should put CMRGlu images and set SPM not to apply any scaling.
If you use global scaling then what you're looking for is whether any area of the brain is "more hypometabolic relative to the average methabolism of the brain". There are also other options using reference regions scaling.
Basically, with CMRGlu you highlight effects that involve the whole brain. With global mean scaling you're looking for very localized effects.
Luca
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Da: SPM (Statistical Parametric Mapping) <[log in to unmask]> per conto di Silvana Prando <[log in to unmask]>
Inviato: sabato 12 maggio 2018 18:03:55
A: [log in to unmask]
Oggetto: [SPM] PET global normalization with proportional scaling
Hi everyone,
I have two groups of patients, A and B, who perform PET with FDG. Both groups did not have pathologies; they were only anaesthetized with different anaesthetics.
In all measures of global mean (SUV, CMRGlu, Ki) for the whole brain, group A has higher values than group B. In comparisons between structures, cortex for example, group A also presents higher mean values than group B. In comparison with SPM, using the global normalization of proportional scaling, the result is that the cortex of group A has a lower metabolism than group B.
Is it correct to analyze the spm result as a hypocaptation in group A compared to group B?
There is another count normalization to apply in this case?
Thank in advance for any help.
Silvana
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