Dear Tyler,
On 18 Feb 2021, at 1:52, Fettrow,Tyler wrote:
> Hi Christian, thanks for the reply.
>
> It makes sense there is not a one-to-one mapping.
>
> However, the coordinates presented in the spm Results GUI (see
> attached png), when viewing the surface data results, seem to
> correspond to MNI coordinates. Is this a rough estimation of surface
> to voxel coordinates?
The use of MNI coordinates for surfaces is rather misleading and not
that useful. I guess this is only used in SPM for compatibility purposes
with the output structure.
>
> Is there a way to pull the surface data out at those reported
> clusters?
You can use cat_surf_results with the data cursor functions. This allows
you to obtain the data at the selected vertex or inside a cluster.
Best,
Christian
>
> Tyler
>
>
> -----Original Message-----
> From: SPM (Statistical Parametric Mapping) <[log in to unmask]> On
> Behalf Of Christian Gaser
> Sent: Wednesday, February 17, 2021 7:19 PM
> To: [log in to unmask]
> Subject: Re: [SPM] MNI voxel coordinates to Surface Vertices
>
> [External Email]
>
> Dear Tyler,
>
> it is not possible to make a one-to-one mapping from voxel to surface
> coordinates. Imagine how the surface intersects or crosses a 3D
> volume, therefore the connection between voxel and vertex is not
> always possible.
>
> Best,
>
> Christian
>
> On Wed, 17 Feb 2021 14:01:20 +0000, Fettrow,Tyler <[log in to unmask]>
> wrote:
>
>> Hi all,
>>
>> I am new to playing with the surface data so I may not be using the
>> terminology properly and apologize in advance. I am trying to figure
>> out how to extract data from specific points from a gifti surface
>> file created by CAT12. Specifically, I would like to convert an MNI
>> coordinate to vertices, or the entry type that is necessary to
>> extract data from the surface files.
>>
>> Digging through cat_surf_results I see on line 3310 "y =
>> spm_data_read(SPM.xY.VY, 'xyz', XYZ)", which grabs the data from the
>> cursor position of the CAT Results GUI. Is it possible to convert
>> from voxel coordinates to this expected ordered vector of vertices?
>> Is there a function embedded in the CAT12 library that does this
>> already, for example, within the ROI analysis portion of CAT12?
>>
>> Thanks for any feedback.
>>
>> Tyler
>>
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