Thank you Dr. Greve for your answer
I checked all about your comment.

I have questions more.
1. I found that volumes or counts in gtm.stats.dat are for native PET space. If co-registered PET onto corresponding MRI(i.e. MRI space) is available using rbv.nii.gz from mri_gtmpvc,
Or if you recommend it by gtm.stats.dat, I can use gtm.stats.dat --rescale (reference regions) for SUVR in PET space.
What do you prefer or recommend?

I'm not sure what you are trying to get. voxel volume or SUVR?

-> Yes. Voxel volume for SUVR analysis.

I compared gtm.stats.dat from both GTM and RBV method.

They were all same SUVR. I think region masks for gtm and rbv are same as pvc-masks, arent they?

2. I used mri_vol2vol --mov rbv.nii.gz --targ original_PET.nii --o test.nii --regheader
because rbv.nii.gz is in different space.
but when overlaid with them, registration is not correct.  (WHY)
rbv.nii.gz is in different space, even not in T1.mgz space. (DKT space)
I just wanted to use the pv-corrected image for image processing.
and you also said, smoothing is required after PVC. (Surface or volume based smoothing (resonable).

The RBV is in anatomical space, if you want to map it back to pet space, you need the registration file in the aux folder (not --regheader).

-> RBV has 0.5mm for voxelsize. even though I put image for input which has 1mm isotropic volume.

You said that 'use in lta file in aux folder'. There are many lta files. So let me know what it is.

- anat2bbpet.lta

- anat2rbv.lta

- bbpet2anat.lta

- bbpet2pet.lta

- pet2bbpet.lta

- rbv2anat.lta

my purpose is this. I want to map rbv.nii.gz to original T1MR space. Could you tell me how to do ?

Thank you so much, Dr.Greve