²Recipe above
does not address problem of having different slice thickness (EPI and/or SPGR)
in different sessions
åBest
solution: pay attention when you are scanning, and always use the same slice
thickness for the same type of image
åOK
solution: use 3dZregrid
to linearly interpolate datasets to a new slice thickness
²Recipe above
does not address issues of slice-dependent time offsets stored in data header from
to3d (e.g., Ôalt+zÕ)
åAfter interpolation to a rotated grid, voxel values can no longer
be said to come from a particular time offset, since data from different
slices will have been combined
åBefore
doing this spatial interpolation, it makes sense to time-shift dataset to a common
temporal origin
åTime shifting can be done with program 3dTshift
íOr by using the -tshift option in 3dvolreg, which first does the time shift to a common
temporal origin, then does the 3D spatial registration
í
¥Further
reading at the AFNI web site
²File README.registration (plain text) has more
detailed instructions and explanations about usage of 3dvolreg
²File regnotes.pdf has some background
information on issues and methods used in FMRI registration packages