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Dear SPM experts,
During the model estimation, the SPM program produces a pile of beta*** files
as well as a mask.img file.
First of all, I
wonder how does SPM create this mask.img.
Second, this mask.img contains gray values ranging from 0 to 1, instead of
logical values (0 or 1) as I thought. Why? And how can I use this mask.img to
extract the inside-brain voxels?
The last one, there are two sets of data which were collected using different
MRI machines. We processed them respectively and got different masks. As
attached please find mask1.img and mask2.img. The former comes from one subject
of the first data set, and the latter comes from one subject of the second data
set. The latter has a sharp edge, whereas the form is something blurred. I have
checked other subjects, the mask images for the first data set are always
blurred, whereas the mask images for the second set are always sharp. What
reason causes the problem? The head motion? Or the difference of the
resolution?
Thanks in advance for any help!
Best wishes!
Lu FENG