zero tracts with Correlational tractography with latest version

[ramtilak gattu]

Hello Dr Yeh,

I have a database with 25 control subjects and 1 TBI patient, featuring spatially normalized fractional anisotropy (FA) mapped to the MNI template, created using DTI Studio and SPM.

We are analyzing correlational tractography for tracts with decreased FA, using a t-statistic threshold of 2.0 and a minimum tract length of 10 mm. Here is a video file for your review  (https://www.dropbox.com/scl/fi/ze5gobsq5qjjvgfk4dsi2/Recording-2025-12-18-115302.mp4?rlkey=dz627fqcbnmjxmhmul0i5dawr&st=38qch7hs&dl=0) and finding everything in order, the latest version of DSI Studio shows no tracts with decreased FA.

In contrast, the version from May 2025 does show some tracts (see attached snapshots). 

Could you help me understand these discrepancies?

Thanks 

Regards

Tilak

[Frank Yeh]

The regression won't provide good result with just 1 TBI patient and
20 controls due to a heavily unbalanced group.
The more suitable approach is to average 20 control to get the average
FA map and use differential tractography to find the affected tract in
the TBI patient.

The online tutorial covered differential tractography and the example
shows how to do this is a more robust way using differential
tractography.

Best regards,
Frank

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