Dear Chung-Haow Tu,
At 19:50 27/05/99 +0800, Chung-Haow Tu wrote:
| According to the Dr. Brett's abstract,
| the scan order effect looks like a movement artifact. So SPM
| will include this in motion correction in feature?
I doubt it.
(We're talking PET/SPECT here, not fMRI, which has motion correction.)
PET/SPECT analyses can have very low degrees of freedom. Assuming motion is
simply a nuisance effect (not confounded with the effect of interest),
inclusion of motion parameters into the statistical model could potentially
have a detrimental effect, by using up more in degrees of freedom than is
gained through a better fitting model. This is therefore a model selection
issue. Thus, inclusion of such covariates needs to be left as a user
choice.
Additionally, there may be alternative pre-processing steps that can remove
some of the artefact referred to by Matthew...
Hope this helps,
-andrew
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