[Mristudio-users] About calculating tensors

[jeongpyo son]

Hi. DTI Experts! 
I'm the new researcher at this part.
I have two questions about tensor calculation.

1. 
After acquired the DWIs, I have calculated tensors using the DTI studio program.
But there are problems about calculated data.
At many voxels (about 3/5 of whole FOV), FA values are overestimated. 
FA > 0.7 of gray matter regions and FA = 1 at almost WM regions.
Eigenvalues of overestimated regions are nagative values.
My data was acquired using Bruker 7T MRI and the subject were SD rats.
Why this problems are occurs?
Is the DTI studio program only for human DTI data analysis?

2. 
For solve these problems, I have a plan to calculate the diffusion tensors manually.
I only know the raw DWI data's signal intensities.
Through them, can I calculate the eigenvalues manually? 
If can, please let me know the calculating procedures (with formula). 

I know that my questions are so bottomless pit. 
But I spent many times for solving this problems and hit the wall.
I need your help!!


Thanks a lot!!