afni.nimh.nih.gov

It is possible to set the size of the warped voxels to be larger than the default 1 mm; in adwarp, this is done with the -dxyz option; in AFNI, this is done on the Define Datamode control panel. A voxel size of 2 mm will produce a dataset that is 1/8 the size of a 1 mm voxel size, since the volume of each large voxel is 8 times larger.

bob cox