Question About Metric Differences Across DSI Studio Versions

[taravat rasooli]

Dear Dr. Yeh,

I hope you are doing well. I am writing to ask for your guidance regarding a discrepancy I observed in diffusion metrics when using different versions of DSI Studio.

In my initial analysis, performed with DSI Studio – Chen Jun 3, 2024, for example, the corpus callosum tract showed this pattern:

FA decreased, while RD, MD, and AD increased.

However, when I repeated the analysis using a newer version of DSI Studio (screenshot attached), for correlation tractography, the pattern changed noticeably:

FA decreased, but RD, MD, and AD also decreased.

(This inconsistency repeated for almost every tract.)

I wanted to ask two questions:

1. Is it possible that not performing preprocessing again in the newer version could lead to this pattern of reduced diffusivity across all metrics?

2. What other factors or version changes might explain this difference?

Thank you very much for your time and guidance.

I truly appreciate your help.

Warm regards,

Taravat Rasooli.

[Frank Yeh]

Older versions may apply 'normalization' which changes the values, and the Spearman permutation in the newer version also handles tie issues better. 

If the study effect is weak with ROI used, it could end up with a different results.  Using length threshold instead of using FDR threshold would avoid unreliable results.

Hope this helps

Frank

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