Hi,

I'm having a weird problem using 3dcalc to create ROIs.

Below are two command lines; one is supposed to create a spherical ROI of radius 4mm at voxel (20 20 69) and the other at (20 20 70).

cmd1:

3dcalc -a AA_spgr_oLIPS_ROI+orig -expr 'step(-a*(((x-20)*(x-20))+((y-20)*(y-20))+((z-69)*(z-69))-16))' -prefix test1

cmd2:
3dcalc -a AA_spgr_oLIPS_ROI+orig -expr 'step(-a*(((x-20)*(x-20))+((y-20)*(y-20))+((z-70)*(z-70))-16))' -prefix test2

Cmd1 above works fine. I get an output brik that is all zeros except within a sphere centered around (20 20 69). But cmd2 returns the following message and creates the output brik test2_orig but it does not contain the desired sphere at (20 20 70).
++ Symbol x using predefined value
++ Symbol y using predefined value
++ Symbol z using predefined value
** WARNING: output sub-brick 0 is all zeros!

What is going on here? Why does it not like the value of 70 or higher for the z coord?
Am I missing something basic here?
Help!

Thanks,
Shruti