[caret-users] white matter point on flattened surface

[Sofia Crespi]

thank you Donna
I would think too!
Sofia
----- Original Message ----- 
From: "Donna Dierker" <donna at brainvis.wustl.edu>
To: "Caret, SureFit, and SuMS software users" 
<caret-users at brainvis.wustl.edu>
Sent: Thursday, May 14, 2009 3:27 PM
Subject: Re: [caret-users] white matter point on flattened surface


> Hi Sofia,
>
> Let's say you have an activation map (fMRI) in volumetric form for your
> subject, for whom you also have a fiducial surface.  Provided that the
> fMRI has been volume-registered to the same anatomical used to generate
> the fiducial surface.
>
> When you map that fMRI volume onto the surface, you always map to the
> fiducial surface.  (Note that the fiducial surface might be a white
> matter, pial, or midthickness representation.  If the surface was
> generated using Caret, it's a midthickness surface.  If it was generated
> using, say, Freesurfer, then a midthickness surface is easily generated
> by averaging the WM and pial surfaces.)
>
> Once the fMRI is mapped onto the fiducial surface, then you have a
> node-scalar mapping that can be rendered/overlaid on any surface
> configuration (flat, inflated, etc.).  But one never maps to the
> inflated/flat surfaces directly.
>
> It's worth mentioning that the Caret surface, being a midthickness
> surface, won't necessarily intersect your white matter voxel.  It
> depends on the fMRI resolution and how the fiducial surface intersects
> the fMRI volume there.  There are various mapping algorithms that help
> you get around this problem (gaussian being the most helpful,
> probably).  But if you have an actual white matter surface available, it
> is possible to map to that, as well.  If the voxel is deep in the white
> matter, it will still not intersect the WM surface, but then it is of
> questionable validity, I would think.
>
> Hope this helps,
>
> Donna
>
> On 05/14/2009 04:45 AM, s.crespi1 at campus.unimib.it wrote:
>> dear Donna
>> I have a we question concerning the overlapping metrical data on the flat 
>> map.
>> If I have some voxel belonging to the white matter how does caret manage 
>> them with respect to the flat?
>>
>> thank you!
>> sofia
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>>
>
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