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
¥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