Hi John,
Thanks
The reason for me to try it out is that in one of my studies I have
PET receptor binding images which I wanted to apply the Dartel field/
plus affine normalization to.
Importing PET (coregistered - not resliced - to the T1 images) using
dartel and subsequently applying the dartel field did not work out as
the import stage failed. Importing resliced PET data works, but would
give an extra interpolation step.
vh
William
On Feb 18, 2008, at 3:10 PM, John Ashburner wrote:
> Hi William,
>
> There is not yet a sraightforwards way of doing this modulation. If
> I was
> doing a VBM study with DARTEL, then I would analyse the Jacobian
> scaled data
> in the average space of the population, and then map any findings to
> MNI
> space. Note that the imported data are rigidly transformed, so that
> the
> Jacobians that DARTEL generates should reflect relative volumes
> (without
> having to factor in any expansion/contraction from an affine
> transform).
>
> For fMRI, the convention is currently to spatially normalise to MNI
> space,
> smooth and then do the stats. There is no Jacobian scaling step in
> there,
> and the steps I outlined were really for processing functional data.
>
> All the best,
> -John
>
>> I successfully ran dartel on several data sets I have. Thanks again
>> for the code below.
>> As I want to report findings in MNI coordinates I followed your
>> guidelines in dartel_guide.pdf and generated a composite of the
>> Dartel flow field and the sn.mat file containing the affine
>> transformation of the template6.nii to the apriori grey.nii and
>> applied it to the c1*.nii files.
>>
>> The next thing I want to do is to modulate the resulting spatial
>> normalized files. I would preferably be able to modulate "Affine+
>> nonlinear" warps and "non-linear" warps only as I would like to look
>> at the effects of using different schemes for correcting global size
>> differences. How would I do this??
====================================================
William Baaré Ph.D. Senior Researcher
Danish Centre for Magnetic resonance
MR-department, 340
Kettegaard AllÈ 30
Hvidovre Hospital tel: 00 45 3632 2978/2885
University of Copenhagen fax: 00 45 3647 0302
2650 Hvidovre mail: [log in to unmask]
Denmark www: www.drcmr.dk/ www.cimbi.dk
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