Dear Mozhdeh,
there are at least two data sets in your first sample and probably also in the 2nd sample that might be potential outliers. I would check data with a much lower sample covariance more carefully and probably exclude them from the analysis. Please also check the quality of the GM segmentations (which are the basis for cortical thickness) and the original data.
Best,
Christian
On Thu, 3 Jun 2021 23:16:56 +0430, Mozhdeh Haddadpour <[log in to unmask]> wrote:
>Hello,
>I implemented surface based morphometry(SBM) on a datasets on which I have
>previously performed VBM in CAT12/SPM12. The results for VBM are as
>expected but, for SBM, I am getting no suprathreshold clusters in both FWE
>& uncorrected p value!!! I was wondering because the datasets are similar
>in both VBM and SBM!!
>Also, I checked smoothed thickness data quality with option of "* check
>sample homogeneity of surface"* in CAT12 such a way that I created two
>samples below Data and in sample 1 I uploaded the control groups smoothed
>thickness data and in sample 2 I uploaded patients group smoothed thickness
>datasets.after running this module results are shown in attached file.
>
>Given this result,are my datasets heterogeneous or not?
>It is worth noting that I just changed the smooth kernel to 15mm and other
>settings in processes of extracting and smoothing & resampling of thickness
>datasets are the same as default.
>
> 1. How can I solve ("no suprathreshold in cluster") problem??
> 2. Which part of the default settings do you think should be changed?(I
> mean "resample size(32k,164k)(I used 32k!!)"?? or "FWMH kernel size"??? or
> other suggestions????
>
>Thanks
>
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