Dear Benno,
I have additionally registered the Dartel Template to the MNI space. The standard approach in the Dartel toobox is to use rigidly registered brains (means without correction for different brain sizes) as input which results in normalized images that have to be finally registered to MNI space. By using the intrinsic MNI transformation in the VBM8 template this step is not necessary. Thus, the final Dartel warped images are already in MNI space.
The recommended use of the VBM8 Dartel template is to rather use affine registered images as Dartel input to already consider the different brain sizes. The advantage of that approach is that less deformations are necessary to register the brains and the normalized brains don't need any final MNI transformation.
Best,
Christian
On Thu, 10 Apr 2014 16:26:55 +0100, Benno Gesierich <[log in to unmask]> wrote:
>Dear SPM Experts,
>
>I would like to use the VBM8 Dartel Template (i.e. Template_1_IXI550_MNI152.nii) as an independent template for my study, using the "Run DARTEL (existing templates)" option.
>However, when I made a comparison, I noticed that the VBM8 Dartel template is quite a bit larger than all our previously created Dartel templates, which in turn are quite similar in size. For example, I show here bellow the VBM8 Dartel template as blue overlay on a Dartel template created from the ADNI study. I have to admit that all our templates were derived from elderly populations. And I know, that the Dartel Template somehow represents the average brain size of the used subjects. But still, the difference in size is quite big, and I was wondering whether this can be due just to an age-related difference in average brain size? Were the brains maybe treated differently in VBM8 before importing them into DARTEL. And, more importantly, can I use the VBM8 template anyways in a standard DARTEL workflow (i.e. not using the VBM8 specific workflow), even if the subjects in my study appear to have on average much smaller brains?
>
>Thanks,
>Benno Gesierich
>
>Institute for Stroke and Dementia Research (ISD)
>Ludwig-Maximilians-Universtity
>Lochhamer Straße 13,
>D-82152 Martinsried
>
|