Hi.
First, we generally discourage concatenation of different session time
series for first-level analyses, but recommend separate analyses which
then get combined at higher-level FEAT anlayses, for various practical and
theoretical reasons.
To run avwmerge, assuming, for each session, that your 120 volumes have
their numbers in the "00001" part, you want
avwmerge -t mp_001 mp_001_00???.img
you can check the order it will use just by typing
echo mp_001_00???.img
Doing the above will allow easy use of the "delete volumes" option in
FEAT.
Thanks, Steve.
On Wed, 9 Apr 2003, Mark Pinsk wrote:
> Hi, just started w/ FSL. I haven't found a clear answer on something that
> seems simple.
>
> Typical experiment session: Ten 4-minute EPI "runs" (TR=2, 120 measurements
> per run, so total of 1200 measurements).
>
> Each measurement is an Analyze file (hdr+img) named like this:
> subject_run#_measurement# (ex: mp_001_00001.img).
>
>
> My first inclination is to avwmerge all 1200 files into one big Analyze
> file. First question: will avwmerge know what order to put all that data
> in (given the numbering scheme shown above) ?
>
> Also, the "delete volumes" option in FEAT does not make sense then, since
> it will just delete the first few measurements of run 1, but not the first
> few measurements of subsequent runs since they are all merged into one
> file. So then it looks like I need to first, manually delete the first
> few .img/.hdr files of each and every run, THEN use avwmerge to put it all
> together, then set delete volumes to 0. Does that seem right to you?
>
> If that IS correct, then I will have to create a very long design matrix
> (unless the conditions occur in same exact order for each run). Is that
> correct?
>
> Alternatively, I imagine analyzing each run separately, then doing some
> sort of group analysis, but that seems counterintuitive to me. Especially
> since all these runs were acquired in same experimental session.
>
> Any help clearing this up would be very much appreciated, thanks!
> Mark
>
Stephen M. Smith MA DPhil CEng MIEE
Associate Director, FMRIB and Analysis Research Coordinator
Oxford University Centre for Functional MRI of the Brain
John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
|