[Mristudio-users] Why deleting b0 from one of the runs increases FA a lot.

[Dorian P.]

Dear developers and Dr. Mori,

I am comparing FA for some tracts at two time points. At each time point I
acquire 2-3 DTI runs to increase SNR. However, the scanner has
malfunctioned for one of the runs in one subject. As a result the B0 image
is not saved, but all other DWIs are there. So, I set the collapsed B0 to
gradient 100, 100, 100 and align all DWIs to the only B0 available. For
some results, the resulting FA is increased a lot.

I tried the same procedure with another subject, when I set one of the B0
to gradient 100, 100, 100, the resulting FA of the tract goes up from 0.51
to 0.62.

Is there any explanation why this is happening, and whether I should delete
completely the collapsed B0 instead of setting it to 100, 100, 100?

Thank you.
Dorian
TJU
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.mristudio.org/pipermail/mristudio-users/attachments/20130927/9da538c8/attachment.html