Batch tractography using GUI

[Maryam Shapourjani]

Hello dear Frank,

Regarding tractography (Batch), there is a parameter called Tolerance which consists of three numbers (by default 22, 26, 30).

The following text is written on the website about this parameter:

"Individuals may have track different a lot from the atlas. This distance value decides whether to consider a valid streamline. A higher value will allow for more complete mapping with the increasing risk of including false connections."

I understand the general concept, but:

• A. Why are three numbers written here?

• B. Does each of these three numbers separately represent a specific concept?

• C. Is the unit of Tolerance and the unit of each of these three numbers millimeters (mm)?

• D. Can these three numbers be the same (e.g., 22, 22, 22 or 22, 22, 26)?

• E. If the subject's streamlines are to be compared with the atlas's streamlines, and the highest Tolerance value means that pathways with a greater distance from the atlas are also selected, then why is there a need for lower numbers for Tolerance? For example, when the highest value is 30, all streamlines from a distance of 0 from the atlas up to a distance of 30 from the atlas are selected. In this context, why is there still a need for lower numbers like 22, when setting the value to 30 already covers 22?
  
  Sincerely,
  Maryam Shapourjani  

[Frank Yeh]

>
> A. Why are three numbers written here?

DSI Studio will try three different settings. If the first does not
give enough tract, then it will use the second.

>
> B. Does each of these three numbers separately represent a specific concept?

No, they are just three parameter values.

>
> C. Is the unit of Tolerance and the unit of each of these three numbers millimeters (mm)?
>

Yes

> D. Can these three numbers be the same (e.g., 22, 22, 22 or 22, 22, 26)?

Yes, but it does not make sense to use the same.

>
> E. If the subject's streamlines are to be compared with the atlas's streamlines, and the highest Tolerance value means that pathways with a greater distance from the atlas are also selected, then why is there a need for lower numbers for Tolerance? For example, when the highest value is 30, all streamlines from a distance of 0 from the atlas up to a distance of 30 from the atlas are selected. In this context, why is there still a need for lower numbers like 22, when setting the value to 30 already covers 22?

Lower tolerance may end up have no result at all, and thus need to try
different values.
Frank

>
> Sincerely,
> Maryam Shapourjani
>
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[Maryam Shapourjani]

Hello Dear Frank,

Thank you for the guidance.

I have another question about the tolerance in Batch Tractography using the GUI, based on this statement: (DSI Studio will try three different settings. If the first does not give enough tract, then it will use the second). If the first value selected for tolerance yields enough tracts, will the software not use the second and third values that were also selected?

Sincerely,
Maryam Shapourjani