[caret-users] caret-users Digest, Vol 75, Issue 10

z丹丹 jidanz at hotmail.com
Mon Dec 28 20:58:07 CST 2009


Hi Donna,

Thanks for your answer. 


> On 12/28/2009 02:55 AM, z?? wrote:
> > Hi Donna,
> >
> > I want to ask a question related to the spherical registration. When
> > we have the original surface, we need to make it into a sphere to
> > register it to a template sphere. After this step, we will get the
> > deformed sphere. Do you have any way to make this deformed sphere go
> > back into the original surface space?
> If you selected a bidirectional deformation (source to target AND target
> to source), then you could apply the inverse deformation to the deformed
> sphere, but in practice no one ever does this, as far as I know.
> 

For the answer, I think you mean I can deform the deformed subject "sphere" back to the  original subject "sphere", while  this is not I want.  What I want is  to put  this  "deformed subject sphere representation" into a "deformed subject fiducial surface representation" .

> The typical reason for deforming in the reverse direction (target to
> source) is viewing atlas "goodies" on the individual's surface (e.g.,
> visuotopic or orbito-frontal parcellations).
> 
> > I mean, after this, I can have one original surface, one deformed
> > original surface which is from the deformed shpere, when I superimpose
> > them together, we can know which part deformed a lot.
> I think viewing the deformation field is probably a better way to do
> this. See figure 5 in David Van Essen's PALS paper
> (http://brainvis.wustl.edu/resources/-Pals.wcover.pdf), panel C.
> This isn't something I do every day, but I think you use File: Open Data
> File to open the deform_field file that gets written during
> registration. Then look at Toolbar: D/C: Deformation Field to see your
> visualization options.
> > Is that possible? Or do you just compare the deformation in the
> > spherical space?
> To be honest, I generally don't look at these deformations. I do sanity
> check the registration output, to make sure the deformed fiducials look
> reasonable and the depth maps are sane looking. Then I do group
> analyses, where depth or coordinate differences are computed and put
> through statistical tests.

I checked the deformation field, so  it shows  the direction of the deformation.  But I still want to know whether I can get the deformed subject sphere in a "fiducial representation". You mentioned you "check the registration output, to make sure the deformed fiducials look
 reasonable and the depth maps are sane looking."  So  what  registration out put do you check? The  landmarks  before and after registration?  And  "deformed fiducials"  is  the  deformed  subject sphere or the real deformed fiducial surface?  If it's the latter one, that is  what I want to get.

By the way, when I register the subject sphere to the template sphere, after registration, there is  a  deformed _*temp*.coord file  (a fiducial surface file, not the deformed sphere). It has the same representation as the template fiducial surface but with the same number of vertices with the subject. I don't think this fiducial surface is the deformed fiducial surface after registration as it algined perfect with the template...it seems it is resampled,  do you know how it comes?

Thank you very much.

Jidan


 		 	   		  
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