Dear Natalia,
the explicit mask is ignoring regions with zero value for the analysis. However, you will still have values which are close to zero and rather belong to white matter or CSF. Therefore, it is recommended to use an absolute threshold of 0.1 or higher to exclude non-gray matter areas from analysis.
Best,
Christian
On Wed, 2 Mar 2016 17:55:15 +0000, Natalia K <[log in to unmask]> wrote:
>Hi,
>Could anyone help me with the masking option in VBM analysis in SPM8?
>I have 2 level analysis (comparing two groups) two sample t-test. I have also age as a covariate and TIV (total intracranial volume) as a globals (global values). The data are also ''modulated'' at Normalization step.
>I used Explicit Mask – gray matter mask. No implicit mask and no threshold masking. Can I use this option ''Expilicit Mask''? Is it appropriate?
>
>Thank you in advice for your help.
|