[WARNING] eddy has not provided rotated bvecs file;using original gradient table

1

Dear experts,

I try to perform the fixel-based analysis of fibre density and cross-section.But there is a WARNING when I using the script of dwipreproc.
The command of I used is following:

foreach * ：mrconvert IN/dwi.nii IN/dwi.mif -fslgrad IN/dwi.bvec IN/dwi.bval -datatype float32
foreach * : dwidenoise IN/dwi.mif IN/dwi_denoised.mif
foreach * : dwipreproc AP IN/dwi_denoised.mif IN/dwi_denoised_preproc.mif -rpe_none

Then occured the WARNING:eddy has not provided rotated bvecs file;using original gradient table.
However, I obtained the output dwi_denoised_preproc.mif finally.
But I did not know the reason that the WARNING occured. And the dwi_denoised_preproc.mif that I obtained is right?

Thanks,
Mirabelle

2

This would indicate that your version of FSL does not perform rotation of the bvecs (requires FSL > 5.0.8, if I remember right). It’s a warning only - dwipreproc will use the corrected bvecs if it finds them, otherwise it will just use the originals, and give you this warning.

Whether this is a problem depends on how much motion you expect in your data. This correction would matter for large motion (rotation in particular), so if you have compliant subjects, I don’t think it’s worth worrying about a great deal.