Dear Ehsan,

If your data is somewhat noisy, it is possible that some voxels inside the brain act in a way that is not physically possible. We will put it on our to do list to add some more check points in the dke_ft script, that will set these voxels to zero or something that is appropriate depending on why the situation is occurring.

For the time being you can manually eliminate that specific voxel from the outputs. Also, i do not think it will affect the tractography results.

Hope this helps,
Best
Emilie