Dear FSL experts,
I ran sienax -r -d on the MNI_152_T1_1mm.nii.gz brain, which was included with FSL. It was my understanding that sienax warps the input brain to the MNI152 brain in order to obtain a scaling factor, used as a normalization for head size. If the input brain is the same as the standard brain to which it is warped during the calculation of the scaling factor, then the volume and un-normalized volumes should be exactly the same. However, I got the following results:
tissue volume unnormalised-volume
pgrey 643267.44 633674.44 (peripheral grey)
vcsf 36549.11 36004.06 (ventricular CSF)
GREY 828226.80 815875.52
WHITE 739654.20 728623.79
BRAIN 1567881.00 1544499.31
I do not understand why this happened - if the standard brain used in sienax is not the MNI_152_T1_1mm.nii.gz brain, what is the standard brain used and where could I find it? Thanks for your help.
Stanley
|