¥AFNI program 3dvolreg is for
aligning 3D volumes
² T[x]
has 6 parameters:
åShifts
along x-, y-, and z-axes; Rotations about x-, y-, and z-axes
²Generically
useful for intra- and inter-session alignment
²Motions that
occur within a single TR (2-3 s) cannot be corrected this way, since method assumes a rigid movement of the entire
volume
¥AFNI program 2dImReg is for
aligning 2D slices
² T[x]
has 3 parameters for each slice in volume:
åShift
along x-, y-axes; Rotation about z-axis
²Useful for
sagittal EPI scans where dominant subject movement is ÔnoddingÕ motion that my be faster than TR
²It is
possible and sometimes even useful to run 2dImReg
to clean up nodding motion, followed by 3dvolreg to deal with out-of-slice motion
¥Hybrid
Ôslice-into-volumeÕ registration:
²Put each
separate 2D image slice into the target volume with its own 6 movement parameters (3 out-of-plane as well as 3
in-plane)
²Has been
attempted by some AFNI users but the results are not wildly better than volume registration; method often fails on
slices near edge of brain
åMore
work is needed (i.e., send money)