Hi - from what you've said I'm surprised that the 3DOF isn't working
right. It's probably easiest if you put example images on a www/ftp site
and we can take a quick look here.
Thanks, Steve.
On Wed, 8 Oct 2003, Johanna Pekkola wrote:
> Hello,
>
> and thanks for your help last time.
>
> Now, I would like to ask for your advice in regisration-related problems.
> I have tried many things but cannot seem to get around this.
>
> For each subject (10) I have EPI-images (28 axial oblique slices with 3.4
> mm slice thickness, T1 FSE images with exactly the same slice prescription
> but better in-plane resolution and a sagittal 3D SPGR volume.
>
> In FEAT registration I have used the axial T1 images as initial highres
> and 3D SPGR as highres. I run into problems in the first registration step
> (epi to initial highres).
>
> With all DOF (3,6,7,9,12) the epi-images seem to get
> tilted in respect to T1 so, that the frontal pole rises and occipital
> areas are lowered. Also, even with 3DOF and no search the stack of
> epi-images is misplaced in respect to T1 so, that there are 2-3 epi-slices
> below the bottommost T1 slice.
>
> Using 7 DOF of more the cranial and caudal limits of epi- and T1 slice
> stacks do correspond to each other quite well but the epi-images are magnified
> so that most of the cortical surface ends up outside the T1 brain area.
> Also, recognizable landmarks such as sylvian fissure are visibly
> displaced between the two volumes.
>
> Am I correct to think that when the same slice presciption has been
> used for epi and T1 the slices should not get misplaced in respect to
> each other like this?
>
> Is there something you could recommend?
>
> With Best Regards,
>
> Johanna Pekkola
> LCE/TKK
> Espoo
> Finland
>
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
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