The "RAS" in that image refers to scanner RAS (not MNI coords).
The "Talarairach" is actually MNI305 (it is called this in version 7 to avoid this kind of confusion).

In case you have not seen it, here is a page that may answer more of your questions.

https://surfer.nmr.mgh.harvard.edu/fswiki/CoordinateSystems

On 5/4/2020 3:48 PM, Hye Bin Yoo wrote:

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Dear Freesurfer Developers,

How are you? We have been using Freesurfer Freeview for localizing implanted electrodes for human brains, and the coordinate system of choice was "Talairach". However, we are trying to utilize MNI152 coordinate system for advanced analyses. How could we transform between the coordinate systems between Talairach and MNI152 using Freesurfer commands? We do realize there are formulae available, but we would like to make sure WHAT coordinates Freeview is actually referring to.

For your information, please find the attached picture. The red squares are on RAS and Talairach, and we assume these correspond to MNI305 and Talairach in MNI space, respectively. Is there an internal formulae we can utilize to obtain the RAS values given Talairach coordinates only?

Thank you very much for your help in advance!
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