Max Censored Displacement

Hi AFNI team,

I am analyzing database resting state images with one functional run each. I noticed in my output that some participants have a large max censored displacement ranging from 1-3. How is this value calculated?

Thank you,

3dvolreg’s help has some information.

-maxdisp = Print the maximum displacement (in mm) for brain voxels.
(‘Brain’ here is defined by the same algorithm as used
in the command ‘3dAutomask -clfrac 0.33’; the displacement
for each non-interior point in this mask is calculated.)
If ‘-verbose’ is given, the max displacement will be
printed to the screen for each sub-brick; otherwise,
just the overall maximum displacement will get output.
** This displacement is relative to the base volume.

Hi Jenna,

You might be referring to the max censored displacement output at the end of an script. In that case, maximum displacement between volreg parameters (Euclidean distance of first differences) among all pairs of volumes (not just consecutive). It can easily get up between 5 and 10 mm (approximate mm).

Just for demonstration purposes, we were dropping subjects for whom that value was >= 8.

See AFNI_demos/AFNI_pamenc/AFNI_02_pamenc/global_process_outline.txt, and search for that “max censored displacement” string.

  • rick