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

History of AFNI updates  

|
January 19, 2005 12:20PM
Wolfgang is correct on all counts here. There have been several papers showing noise at highly anisotropic values give negative eigenvalues. Unfortunately, the FA values are not really defined for those cases. GE (I hadn't known this) and DTI Studio change the negative eigenvalues to 0.0. Bob Cox has come up with a modified algorithm that takes into account the noise. I've been working on an update to this software to implement that algorithm.

In the meantime, Wolfgang's suggestion may be the best choice. Do a manual masking of the negative eigenvalues and recalculate the FA.
Subject Author Posted

FA image thresholding

Brian Schweinsburg, Ph.D. January 17, 2005 08:47PM

Re: FA image thresholding

Wolfgang January 17, 2005 10:29PM

Re: FA image thresholding

Daniel Glen January 19, 2005 12:20PM

Re: FA image thresholding

Brian Schweinsburg January 19, 2005 12:27PM