> In the SPM99 manual, page 84, there are nicely rendered brains. I tried to
> create that kind of brain surface with the single_subj_T1.img in the
> canonical folder. The following is what I did:
>
> 1. segment single_subj_T1.img (choose "NO" when prompted "Are they
> spatially normalized?"; "Modality"-->"T1-MRI"; "No inhomogeneity
> correction.") 2. select "Xbrain" in Display, choose
> "single_subj_T1_seg1.img" and "single_subj_T1_seg2.img"
>
> However, the rendered brain does not look right (as shown in the attached
> figure). They are too smooth at some locations. The brain extraction I've
> done seems not producing the same effect as shown by the
> render_single_subj.mat. Did I do anything wrong with segmentation or brain
> extraction? Or I missed some steps?
You did all the right steps.
The single subject dataset that render_single_subj.mat was based on had an
isotropic resolution of 1mm. In order to reduce disk space downloading time
etc, I reduced the size of the dataset by a factor of 8 by reproducing with
voxels of 2mm. There is simply not enough detail in the downsampled data
to derive a reasonable cortical surface.
The renderings in the manual is derived from a high resolution dataset.
Best regards,
-John
--
Dr John Ashburner.
Wellcome Department of Cognitive Neurology.
12 Queen Square, London WC1N 3BG, UK.
tel: +44 (0)20 78337491 or +44 (0)20 78373611 x4381
fax: +44 (0)20 78131420
http://www.fil.ion.ucl.ac.uk/~john
mail: [log in to unmask]
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