Good Afternoon,

I am trying to use the tractography command 3dTrackID for the first time today. I have two questions about this command:

1. Does the input tensor dataset HAVE to be a direct output from AFNI's 3dDWItoDT command? I am asking because I am trying to perform a tractography analysis on a DTI template from the Illinois Institute of Technology (http://www.nitrc.org/frs/?group_id=432) and I do not believe they used this command to create their tensor files.

2. I noticed in the documentation for 3dTrackID that INPREF_V1, INPREF_MD, INPREF_L1, and INPREF_FA volumes are needed to perform the tractography. What I have tried is using 3dTcat to concatenate the principle diffusion direction vector (V1), the mean diffusivity volume (which I calculated using L1, L2, and L3 from the link I posted above), the principle eigenvector (L1), and the fractional anisotropy (FA). When I tried to run 3dTrackID with 2 ROI's (-logic AND), I saw the following output in the terminal. What may this error be suggesting that I am doing wrong?

| ++ version: MU
|
|
|MemAlloc failure.

Thank you,
Nikolai