¥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)