Steve,
some more points to add to the previous query...even though the
registration page on the feat report looks ok my activations on highres
overlay doesn't. i wondered if the problem might be a failure to match
pixel sizes in the different images. for one subject both 24 slice
functional EPI and 120 slice EPI ('initial sturctural') have pixdims
3,3,3 but for another subject the 120 slice is 4,4,3. i don't know why
the latter is different for one of the subjects. could this difference
between the 24 slice and 120 slice image for one of the subjects be
causing a problem? and do i need to set some parameter (eg one of the
advanced options) in flirt to allow for the fact that my 24 slice
functional EPI (and 120 slice EPI) has slices at an oblique angle?
thanks for your help
Jane
In message
<[log in to unmask]> FSL
- FMRIB's Software Library <[log in to unmask]> writes:
> Hi - it's difficult to judge registration quality by looking at the
> activation overlay - you should be clicking on the registration
> evaluation image towards the bottom of the FEAT webpage report and
> look at the detailed registration evaluation images - do they look ok?
>
>
> Cheers, Steve.
>
>
> On Mon, 17 May 2004, Jane Aspell wrote:
>
> > Hi
> >
> > I'm having some problems registering my functional data onto a highres
> > image of an individual subject's brain. My functional data is in the
> > form of 24 obliquely oriented slices mainly covering the occipital
> > area (it's a vision study). The clusters of activation seem to 'flame
> > out' from the brain in some areas, into 'space' by a few millimetres.
> > This problem seems to be worse in occipital areas and not so bad in
> > parietal areas. I have an idea that occipital areas are subject to
> > more distortion than other areas - is this true? To register my
> > functional to a highres with flirt i did a 7 parameter global rescale
> > transformation from my 24 slice functional data to a 120 slice EPI
> > (slices at the same angle as the functional) and another 7 param
> > global rescale to my individual highres structural. is there anything
> > you could advise i do to improve my registration?
> >
> > many thanks for your time,
> >
> > Jane Aspell
> >
>
> Stephen M. Smith DPhil 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
>
--
Dr Jane Aspell Department of Experimental Psychology, University of
Oxford, South Parks Road, Oxford, OX1 3UD tel: +44 (0)1865-281606
|