Hello all,
One reason the 1.5 x 1.5 x 1.5 mm size is suggested is that DARTEL is
computationally intensive, and a lot of people have experienced
problems using smaller voxel sizes. Given that the regions we are
interested in are typically not so tiny, and there is usually
smoothing involved, this seems like a reasonable decision. I.e. it
may not be worth trying to get a smaller resolution. (Using standard
segmentation, the GM/WM images were usually saved a 2 x 2 x 2 mm
resolution, anyway, so historically there has always been a loss of
some spatial resolution when doing VBM...)
If you run segmentation (or the new segmentation, which perhaps you've
been using), the resulting GM/WM images can have a different
resolution than you put in. So if you segment your .938 x .938 x 1.5
mm image, you should still be able to get images for DARTEL (i.e., the
rc* images) that are isotropic, either automatically (from New
Segment) or by importing the images from standard segmentation.
(Someone else please chime in if there's still a problem here!)
Best regards,
Jonathan
On Thu, May 13, 2010 at 8:44 AM, jmanjon <[log in to unmask]> wrote:
> Hi Ajay,
>
> I don´t know what people is doing out there but I would suggest you to go to
> 0.938 mm^3 not to 1.5 mm^3. If you chose the first option you maintin your
> resolution but if you use to the second you loose resolution so the choice
> is quite clear.
>
> hope this helps
>
> Jose
>
>
> Ajay Kurani escribió:
>>
>> Hi SPM users,
>> I have read that in order to use DARTEL the GM/WM images must be imported
>> as isotropic voxels after rigid body transformations. My original image is
>> .938x.938x1.5 so would my isotropic voxels be of since 1.5x1.5x1.5 or can i
>> go smaller by reslicing the image? Also, is reslicing only used when
>> comparing fMRI data or can I reslice my T1 weighted image for VBM analysis?
>>
>>
>> Thanks,
>>
>> Ajay
>>
>>
>
>
> --
> ________________________________________________________
>
> Dr. Jose V. Manjón Herrera ------- [log in to unmask]
> home: http://personales.upv.es/jmanjon
> [IBIME - Biomedical Imaging Area]
> BET - Bioengineering, Electronics and Telemedicine Group
> UPV - Politechnical University of Valencia - Spain
> ________________________________________________________
>
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