Hello Freesurfers

I'm starting to work with DTI data and I have a couple of questions; I have 2 identical DTI sequences for some subjects and I would like to work with them, does anyone knows if it's better to concatenate them or to make an average of them?

And I'm wondering when I make an eddy-current or motion correction (alignment to the B0 or T2) if there is any algorithm to change the vectors to the corresponidng alignment?

Best Regards

Gabriel