Question about hippocampus tractography

Hello,
i am trying to get FA value of hippocampus and draw tractography.
After doing all the preprocessing, i did brain parcellation with freesurfer. so i have this template that divide brain in each part.
i used mrcalc to make get hippocampus mask and used mrgrid to make fa.mif and hippocampus template aligned. then with mrstats i got the number (fa value) is this the right way to do it? the reason why i am concerned is that i tried to draw tractography with tckgen i got tractography. is it because i used whitematter fod.mif file?