>
>I try to setup the study. I have one group of controls (N=43) in 4d
>analyze format and another groups of disease (N=7). I use the first
>level analysis and number of analysis is 2 ( 2 groups of patients ?).
>The TR=3, High pass filter cutoff=100. Turn off the FILM prewhitening
>and turn on the intensity norm. Then the FSL ask to setup model contrast
>details after I push the go. Is there any thing should change ? Thanks
If I can just add my $0.02... The thing to remember about PET data is that
it is *not* a time series.
So you definitely don't want to include a highpass filter (ie turn off
temporal filtering). Similarly, the
concept of TR is pretty meaningless in PET so you might as well set it to 1
and simply use it as an
scan index in your model.
I may have missed the relevant previous posting but do you only have one
scan per subject (ie like a resting
FDG or SPECT image)? And are you only interested in computing a group
comparison patients vs. controls?
For more sophisticated models (like multiple conditions per subject) you'll
need a slightly more
complicated model.
Also, you might want to think about how to best remove global effects. If
I remember right (and
Steve please correct me if I get this wrong), Feat's intensity
normalisation is a global scaling. In
most PET studies people use subject-specific scaling either to the
subject-global means or by
including the scan mean intensity as a covariate (AnCova scaling in SPM-speak).
Good luck!
Joe
Joseph Devlin, Ph. D.
FMRIB, Dept. of Clinical Neurology
University of Oxford
John Radcliffe Hospital
Headley Way, Headington
Oxford OX3 9DU, U.K.
Phone: +44 (0)1865 222 738
Fax: +44 (0)1865 222 717
Email: [log in to unmask]
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