Hi, Sondos-

That is not the correct way to provide the "-dti_in .." input. What comes after the "-dti_in" option is not a list of files (which is what is currently being provided). It is just the *prefix* of the files created by tensor fitting.

For example, if your output from tensor fitting created a lot of files in the "/Users/" directory called:
dti-afni_MD.nii.gz, dti-afni_FA.nii.gz, dti-afni_V1.nii.gz, dti-afni_V2.nii.gz, dti-afni_V3.nii.gz, dti-afni_L1.nii.gz, ...

Then you would enter the commoon part of their prefix to the option name, such as:

3dTrackID -dti_in /Users/dti-afni ....

with all the rest of your options.

Please see the EXAMPLES section at the bottom of the 3dTrackID help file for more cases of this.

--pt