[Mristudio-users] bug in DTIstudio 3.0 (beta) tensor calculation?

[Yi Jiang]

Dear All,

I have a DTI dataset with 1 b0 and 6 DWIs, matrix size 512x256x256 each. I 
tried both the 64bit version 2.4.01 (Oct 2007) and 64 bits version 3.0.0 
(Sep 2008) DTIstudio to do DTI tensor calculation.

For the version 2.4.01, no matter I used automatic outlier rejection or not, 
with all default settings (such as the background threshold is 10), I was 
able to obtain reasonable diffusion tensor images such as FA or colormaps.

For the version 3.0.0 Sep 2008, if I used the standard linear fitting 
method, the resulted images were all reasonable.

If I used automatic outlier pixel rejection, the resulted images (FA, 
colormap, eigenvalue etc.) were all zero.

If I used the automatic outlier image rejection when its error > 3% 
(default), the resulted images (FA, colormap, eigenvalue etc.) were all 
zero.

If I used the automatic outlier image rejection when its error > 99%, the 
resulted images (FA, colormap, eigenvalue etc.) were all zero.

The weird thing is I have use the default settings in the version 3.0.0 
(with automatic outlier image rejection when its error > 3%) to calculate 
diffusion tensors for some other datassets (1 b0 and 12 DWIs, matrix size 
512x256x256 each), the resulted images were all reasonable. Only for this 1 
b0 and 6 DWIs one (similar or better SNR than the other 12 direction DTI 
datasets), the results are not consistent.

Can anyone help? Thanks a lot!

Best,
Yi