Preprocessing data: timeshifts

AFNI Message Board
1

Hi all,
I often see in papers that the first two preprocessing steps they use are:
First, compensation of systematic, slice-dependent timeshifts.
Second, elimination of systematic odd-even slice intensity differences caused by interleaved acquisition.

I’m a little confused with the second… Aren’t odd-even slice intensity differences caused by slice-dependent timeshifts as well? Aren’t these two steps talking about similar things?

Also, I understand that you can deal with one of these problems in afni using interpolation (tshift), right? What about the other?

Thanks for your advice.
Best,
Ana

2

Hi Ana,

Those 2 steps certainly seem like they might be the same, and what we do using 3dTshift. Perhaps the latter one could have something to do with motion, though without real details in the paper, one can only guess. If you run into more details to help figure it out, please feel free to post them.

  • rick
3

Thanks, Rick. I will.