Quote
# FA
4.130704e-01 4.096045e-01
4.096045e-01 3.369234e-01
Then, what should I write the FA value on the paper?
is it 0.409..?
Yes. Calling your target ROIs #1 and #2, then 0.41 (is probably how I would report it-- two significant figures seems appropriate for FA, perhaps three, but I guess that is a combination of a style and study design choice) is the average FA value in the set of voxels estimated to be the WM connection (=through which a suprathreshold number of tracts passed) between target #1 and #2.
Re. the other values (which are on the diagonal): 0.413 is the average FA in the set of voxels estimated to be the WM passing through at least target #1 (could go through #2, or could not, as well); 0.337 is the average FA for voxels in WM passing through at least target #2.
--pt
