Dear Friends,
I am new to CONN. I am working on animal data which infidelity requires different parameters from human data in the pre-processing step.  My question will be feeding my ROIs (before or after processing) to first level connectivity analysis step. My anatomical data is a volume with 80*64*20 dimensions.
I am planning to go to matlab and

1-) use 'imroi' routine,
2-) save the mask as nii
3-) Upload the newly generated nii as ROI.

However, my question is that: should circumscribe (whatever) a region in each 2D images in my volume? If I apply imroi only first 3-4 2D images of the volume, will the output be accurate?
Best Regards,
Mustafa