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
>
>