I just found the command to do this. 
mri_vol2vol --mov PET --reg mri_coreg.lta --fstarg --o rPET


On Tue, Jun 28, 2016 at 10:48 AM Pradeep <tpradeep@gmail.com> wrote:
Hello All, 

I am trying to extract the SUV values a PET image

mri_segstats --seg wmparc.mgz --sum petsuv.segstats.dat --i rPET --ctab-default

since rPET is supposed to be coregistered to MRI, I did the following 

mri_coreg --s MRI --mov PET --lta mri_coreg.lta

which did not generate the coregistered image but just transformation.

Is there a way to generate this image or to just input the mri_coreg.lta as a flag to mri_segstats?

Thanks,
Pradeep