Recently there was some discussion between colleagues as to the merits or
necessity of global scaling when one is comparing two groups with known
anatomical differences (i.e., age-related atrophy). It's my understanding
that scaling is not necessary because this is already handled in SPM as a
default and that it is most important for PET/SPECT, but others were working
off the assumption that scaling would be best because signal intensity may
vary as a function of age. What would be the effect and/or reasoning behind
using the scaling option at the individual level for eventual RFX comparison
between young and old?
Thanks,
Jeff
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Jeff Browndyke
Duke Univ. Med. Center
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