Dear all,
I am sorry if this is a very basic question, but I have not managed to
find any documentation that helps with this problem (if there is any
available, please let me know).
I have some SPET data which is in the form of four scans per subject
(two scans on two separate days). The first scan on each day was a
baseline scan, and the following scan was during infusion of either
active compound or placebo.
I am wanting to compare changes from baseline in the placebo and active
case.
So far, I have tried the following in SPM2:
PET: Multiple subjects, conditions and covariates,
9 subjects,
1=baseline-placebo scan
2=placebo scan
3=baseline-active scan
4=active scan
conditions=0101 (is this right??)
covariates=0
nuisance var.=0
global normalisation=none
no grand mean scaling
threshold masking=relative 0.8
global calculation=mean voxel
non-spericity?=no
contrast: t: 1 -1 (active<placebo)
contrast t: -1 1 (placebo>active).
threshold p=0.001
voxels=30
A lot of this was guesswork and trial and error, but I now have results
that are similar to using the standard ROI approach. My question is
whether I am actually measuring what I intend to?
I could really do with some help on this and would appreciate any
pointers.
Best wishes,
James Stone
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