Hi Linda,

I am not sure what distance you are trying to measure, but perhaps this would help.
Say you have a location identified on a subject's surface in SUMA. You can click on that location and note the coordinate, then you can use Vecwarp to transform each coordinate to TLRC space.

All of this assumes that you are using the proper -sv volume for each subject. This can easily be checked by making sure the surfaces in SUMA overlay properly on the volume in AFNI for each one of your cases.

Note that there are ways to automate all of this, but it is easier for the first pass to try it by hand. If you want to automate, you can use the output of SurfClust to get the peak coordinates, then transform them with Vecwarp as you did above.

An alternate way is to make use of the standard meshes. Say you pick a location from subject s1 that falls on standard mesh node 12, then the equivalent TLRC/MNI location on the same standard mesh of the TLRC_N27/MNI_N27 brain would be found on node 12 of that mesh. So simply get the node indices from subject s1 and get the coordinates at those indices but from the TLRC_N27 ot MNI_N27 brain.

cheers
Ziad


> And Now I can get the peak position of the
> stimulate response both in afni and SUMA
> coordinate system.
> Now I want to calculate the distance different
> within the same subject between two scan.
> In the afni coordinate systerm, I know that I
> need to convert all the subject to the standard
> template. So that they can compare the distance
> with each other. Because some subjects brain are
> bigger.
> My question is: if I use the peak position in
> the SUMA coordinate system. ( I do not use the
> 3dvol2surf). But only use the above way. If I can
> compare the distance between subjects without
> convert all the subject to the standard template.
> Thanks very much!
> Linda