Hi Wafaa,

I think there may be a couple of issues.

1) Did you average your 9 B0 images so that there is only one at the beginning of the 4D Nifti?
2) I can't remember 100% if you can use a different number of directions for each b value, but if you can, I think you'll need two separate gradient vector files since you use 30 directions and then 60 directions. (Look at previous posts in this forum - I think this query has been addressed previously).

Also, if you attach your parameters file, 4D Nifti, and bvecs files people can try to debug it for you.

Cheers,

Kirk