Hi -
These bvals and bvecs look ok to me.
A couple of things Things to check for in your data:
1) The first volume should be much brighter than all the others
(as there was no diffusion weighting applied)
2) In the other volumes, you should be able to
pretty much guess the orientation of the gradient directions
(and hence the elements in bvecs) by looking at the data in that volume.
For example, one side of the corpus callosum will be dark in the image
where the orientation is +x+y, and the other side will be dark in +x-y.
One side of the cortico-spinal tract will be darker than the other for
+x+z, and vice-versa for -x+z etc. etc.
If all of this is ok, then I'm out of suggestions, can you put your data
on a website or ftp site, and email me with instructions for getting it
(please do not send it by email)
Cheers
Tim
-------------------------------------------------------------------------------
Tim Behrens
Centre for Functional MRI of the Brain
The John Radcliffe Hospital
Headley Way Oxford OX3 9DU
Oxford University
Work 01865 222782
Mobile 07980 884537
-------------------------------------------------------------------------------
On Thu, 21 Oct 2004, Lin-Ching Chang wrote:
> Hello, Tim,
>
> Thanks very much for your answer.
> Yes. it is very helpful.
>
> I can run the DTIFIT now and all of slices were processed. However, each
> created tensor map is all like a mask. For example, the values of FA in the
> brain are all ones.
>
> Maybe the bvals and bvecs files I created are incorrect?
> Here is the content of my bvals file
> 0.0 1000.0 1000.0 1000.0 1000.0 1000.0 1000.0
>
> Here is the content of my bvecs file
> 0.0 0.70711 -0.70711 0.0 0.0 0.70711 -0.70711
> 0.0 0 0.0 0.70711 0.70711 0.70711 0.70711
> 0.0 0.70711 0.70711 0.70711 -0.70711 0.0 0.0
>
> I ran the bedpost_datacheck and everything seems OK.
> Whatelse can I check?
>
> Best,
>
> LC
>
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