Hi , I was running FIRST following user guide , and execute the below command : first_flirt con01 con01_to_std_sub ${FSLDIR}/bin/slicesdir -p ${FSLDIR}/data/standard/MNI152_T1_1mm.nii.gz con01_to_std_sub.nii.gz The registered file is attached . Questions : 1. It seems that the registered brain(i.e. con01_to_std_sub.nii.gz) is larger than the standard brain of MNI152_T1_1mm.nii.gz . Is it normal ? Should't they be equivalent between the registered brain and the standard brain ? 2. How good is the registering result ?Generally how to asses the registering result ? compared with the standard brain by visual inspection? I am at a loss . Regards . Xin-Fa Shi .