Dear Alle,
Yes - you're right. My mistake. It should read that slice 9 is
acquired 1.5 seconds
*after* slice 10. I'll fix that.
Rest assured, however, that the implementation of slicetimer in FSL
is fully
tested and correct, even though we do not recommend using slice
timing correction.
The use of temporal derivative instead, is of course driven by the
data and hence
without problems of this kind.
All the best,
Mark
On 11 Jan 2008, at 09:19, Alle Meije Wink wrote:
> Hi,
>
> I was looking at the course notes about slice timing correction
> (http://www.fmrib.ox.ac.uk/fslcourse/lectures/feat1_part1.pdf, page
> 7 and further).
>
> It says: slice 9 acquired 1.5s before slice 10, and the picture
> shows that in slice 10, the measured response also appears to be
> 1.5s *later*. Could it be that that should be 1.5s *earlier* instead?
>
> In this very simplistic diagram
>
> -------------------------------------------------------------- t
> ################################################
> ###########################
> ##############
> response
> #######
> ###
> | |
> t9 t10
>
> The time axis of slice 9 has its origin at time t9, and the axis of
> slice 10 has its origina at time t10.
>
> In terms of the design matrix, the regressors in slice 10 would be
> shifted backwards (showing responses earlier than slice 9)? In
> terms of the data, the time signals would be shifted forward, I guess?
>
> with best wishes
> Alle Meije Wink
>
|