Hi,
No - that's fine if it is small head changes in the same session.
What *does* really make a difference is taking the subject out and
repositioning them in the scanner (either on the same day or on a
different day). In this case we recommend getting a new fieldmap
for the new session, as the position changes can be much greater
this way, and also changes in sinuses and so on (e.g. getting a
cold) can make a substantial difference.
All the best,
Mark
On 14 Jul 2011, at 09:34, Torsten Ruest wrote:
> Dear Mark,
>
> thank you for clarification. I was aware that the fieldmaps and the EPI data are realigned during the preprocessing step using feat, but from previous posts to the mailing list I assumed that slightest changes to head position even within the same shimming setup may render the fieldmap invalid. Anyway, that was really helpful.
> Cheers,
>
> Torsten
>
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