Just a thought, since it appears that you may be using 'mricro' to get
the image values: Is 'mricro' properly respecting the scaling
information (scl_slope and scl_inter) contained in the nii headers?
Also, if you're using modulation, then aren't values > 1 possible, since
you're now measuring relative "volumes" rather than densities?
cheers,
-Mike H.
On Fri, 2010-05-28 at 01:52 +0800, lion gao wrote:
> Dear Christian Gaser,
>
> Thanks for your great work on VBM8. It make segmentation easier.
> Previously VBM5 or SPM5, SPM8 may fail to segment some T1 images
> (about 10%, e.g. gets strange C2. images), Now VBM8 seems work well
> and never fail to segment so far.
>
> One problem I find is that when I compare the images segmented by VBM5
> and VBM8, they looks quite different. and indeed their volumes differ
> a lot. Mainly, the grey matter volume in VBM8 is smaller than VBM5,
> whereas the white matter volume is bigger. the TIV changes little. I
> segmented several subjects from different groups. e.g. from young, old
> group and patient group, this trend is similar among the groups.
> please note that I use the default setting in both VBM5 and VBM8,
> which are normalized modulated segmentations.
>
> Attached pls find a figure for your reference. I wonder is there any
> reason for this. and which result may be better. BTW, another thing is
> that I find the density in white matter from VBM8 can be 2.0778, which
> those in VBM5 are all less than 1.0. So what's the meaning of 2.0778.
>
> Would you please help me to understand these issues. Sorry that if you
> have demonstrated these points in VBM8 manual. I have not read it
> thoroughly.
>
> Best wishes,
> Gao
>
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