Hi,

My goal is to align the EP data collected from two sessions in the same participant on different days. So to acheieve this, I was trying to first align the MP datasets collected in the two sessions and I encountered a problem with 3dvolreg when doing this. I am running on a Linux machine and using linux_gcc32 binaries.

To provide more details, the EP data in these two sessions was collected in the oblique slices, so following suggestions from Daniel, I realigned the MP's in both sessions to respective oblique EP's in that session using

##session1
3dWarp -card2oblique VD12a_EP+orig. -prefix VD12a_MP_algntoEP VD12a_MP+orig.

##session2
3dWarp -card2oblique VD12b_EP+orig. -prefix VD12b_MP_algntoEP VD12b_MP+orig.

Then I used

@Align_Centers -base VD12a_MP_algntoEP -dset VD12b_MP_algntoEP

Now I tried to align the MP from sess2 to sess1 using 3dvolreg and couldn't succeed.

[srikanth@memphis VD12]$ 3dvolreg -twopass -base VD12a_MP_algntoEP+orig. -prefix VD12b_MP_algntoEP_shftR VD12b_MP_algntoEP_shft+orig.
++ 3dvolreg: AFNI version=AFNI_2007_05_29_1644 (May 30 2007) [32-bit]
++ Authored by: RW Cox
malloc failure for image space: 532261120 bytes
in file: mri_new.c at line 193
mri_new_7D_generic
mri_to_float
mri_3dalign_setup
3dvolreg main


As a matter of curiosity, I tried registering the MP's again but now they are not aligned to oblique EP's, and then it worked properly.

[srikanth@memphis VD12]$ 3dvolreg -twopass -base VD12a_MP+orig. -prefix VD12b_MP_shftR VD12b_MP_shft+orig.
++ 3dvolreg: AFNI version=AFNI_2007_05_29_1644 (May 30 2007) [32-bit]
++ Authored by: RW Cox
++ Max displacement in automask = 10.13 (mm) at sub-brick 0


So I am not sure why 3dvolreg failed with oblique looking MP's. It looks like some kind of memory problem. Can someone help me with this?

Thanks,
Srikanth.