[Freesurfer] Cortical surface tessellation and smoothing

2007-06-25 Thread Kai Li 

Dear list,
   Is there a paper or any documentation describing how freesurfer 
tessellate and smooth cortical surfaces? In particular, does freesurfer 
use any specific variety of marching cube isosurface algorithm? Regular 
surface smoothing (like the Laplacian smoothing) may cause undesired 
surface shrinking. It looks that freesurfer does a good job on surface 
smothing. So I'm wondering what smoothing algorithm freesurfer employ.


Thanks,
Kai
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Re: [Freesurfer] Cortical surface tessellation and smoothing

2007-06-25 Thread Bruce Fischl 

Hi Kai,

it was described in the Dale, et al. 1999 paper in NeuroImage, or maybe 
part in 
that and part in the 2nd part of it (Fischl et al., 1999 also NeuroImage). 
They are both on our wiki (surfer.nmr.mgh.harvard.edu/fswiki). We don't use 
marching cubes, but a custom tesselation algorithm. The surface smoothing 
is like a Laplacian, but the surface area of the inflated surface is 
constrained to be the same as the original surface.



cheers,
Bruce


On Mon, 25 Jun 2007, Kai Li wrote:


Dear list,
  Is there a paper or any documentation describing how freesurfer tessellate 
and smooth cortical surfaces? In particular, does freesurfer use any specific 
variety of marching cube isosurface algorithm? Regular surface smoothing 
(like the Laplacian smoothing) may cause undesired surface shrinking. It 
looks that freesurfer does a good job on surface smothing. So I'm wondering 
what smoothing algorithm freesurfer employ.


Thanks,
Kai
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