What are the reasons for this phenomenon in the visualization results of diffusion tensor imaging (DTI) fiber tracts in brain imaging?
What phenomenon do you mean?
Your tensor glyphs appear to be incorrectly rotated, suggesting incorrectly interpreted gradient directions. You can investigate/correct this with dwigradcheck
The black glyph is probably a tensor with (large) negative eigenvalues. You can avoid this by estimating the tensor using dwi2tensor -constrain … from the dev branch.
