AFNI Message Board

Dear AFNI users-

We are very pleased to announce that the new AFNI Message Board framework is up! Please join us at:

https://discuss.afni.nimh.nih.gov

Existing user accounts have been migrated, so returning users can login by requesting a password reset. New users can create accounts, as well, through a standard account creation process. Please note that these setup emails might initially go to spam folders (esp. for NIH users!), so please check those locations in the beginning.

The current Message Board discussion threads have been migrated to the new framework. The current Message Board will remain visible, but read-only, for a little while.

Sincerely, AFNI HQ

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Lukas Pezawas
March 31, 2003 06:20PM
Hi Doug!

I would like to learn some more details about the "cliplevel" part of your normalization procedure posted:
[afni.nimh.nih.gov]

You mentioned that values close to zero would make the normalisation inaccurate. As I understand, this the reason, why voxels close to zero are set to zero in this formula.
However, this clippling procedure will also zero out brain voxels, which are located in the orbitofrontal brain region. These voxels are lower intensity voxels due to the suseptibilty artifact, which starts to show up in this region.

In the context of my current study it would be nice to save these voxels from being zeroed out.

I would like to know more about the background, why these values are inaccurate and would there be any possibilty to use any masking procedure instead?

Thanks,
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Subject Author Posted

percent signal change

Lukas Pezawas March 31, 2003 06:20PM

Re: percent signal change

B. Douglas Ward April 01, 2003 11:48AM

Re: percent signal change

Lukas Pezawas April 01, 2003 01:40PM