No, the RAS in fsaverage is in MNI305 space, so no need to do the conversion.

On 9/27/2021 11:22 AM, Kennedy, Bryan wrote:

Good morning,

We are trying to conduct a meta-analysis by mapping reported MNI dimensions (by others) on fsaverage. I know that I have to use the following conversion:

MNI305RAS = TalXFM*Norig*inv(Torig)*[tkrR tkrA tkrS 1]'

in which,

Norig = [-1.00000 0.00000 0.00000 128.00000; 0.00000 0.00000 1.00000 -128.00000; 0.00000 -1.00000 0.00000 128.00000; 0.00000 0.00000 0.00000 1.00000]
Torig = [-1.00000 0.00000 0.00000 128.00000; 0.00000 0.00000 1.00000 -128.00000; 0.00000 -1.00000 0.00000 128.00000; 0.00000 0.00000 0.00000 1.00000]

When I checked TalXFM, it was just the identity maxtrix (in fsaverage/mri/transforms/talairach.xfm). So,

RAS = inv(Norig)*Torig*MNI;

But based on that, MNI and RAS would be the same coordinates. For instance:

MNI(16 -67 39) -> RAS(16 -67 39)

Are we missing something? Do these numbers make sense to you?

Thanks in advance,

Bryan