SPM - What is the type of the segmentation results files?


I’m a new in neuroimaging and I have segmented Nifti structural MRI with SPM12 into grey matter. I got as result the file rwc1<original_filename> but I was wondering two things :

  1. What is the type of this file ? Is it Nifti like the original ?
  2. Most important question : Do the number in the MRI matrix correspond to the voxel intensities (like in the original) ? Or do they correspond to probability map ? I ask this because I heard about applying a mask on the original image to get the grey matter.

Thanks in advance

Ok, I think I have my answer : It corresponds to probability map.

But I still have a question : SPM proposes “modulated” option for warped tissue. They say that it normalizes the intensity of the whole image. But if we get probability and not voxel intensity, I don’t understant how we get the normalized intensity.