[MINC-users] Thickness analysis

[Jason Lerch]

On Jun 19, 2005, at 10:43 PM, Fornito, Alexander wrote:

> 	
> Hi,
> I've been reading your papers on thickness analysis (MacDonald, et al, 
> 2000, NeuroImage, 12; Lerch and Evans, 2005, NeuroImage 24) and I was 
> seeking some clarification on the nature of the surface that is 
> generated. The MacDonald paper states that the final surfaces created 
> contain 81, 920 triangles. The Lerch and Evans paper states that the 
> number of 'nodes' generated is 40, 962, which is about half that 
> quoted by MaDonald et al.
> My questions:
> By 'nodes' do you refer to vertices?
> Is 40, 962 the number of vertices per hemisphere, whereas 81, 920 the 
> total number for both hemispheres?
> If so, my next question is, wouldn't the number of vertices be greater 
> than the number of triangles?

Nope. Both papers are correct - remember that a single node/vertex 
belongs to multiple polygons. So we do in fact normally use surfaces 
consisting of 40,962 vertices and 81,920 polygons.

>
> Lastly, is the T link algorithm for calculating thickness available 
> for download, and can it be applied to calculate thickness of surfaces 
> using other methods (eg., freesurfer)?

Not really - the link algorithm is the one (of the six) that is the 
most dependent on our method of extracting surfaces, and would thus not 
work with freesurfer.

Cheers,

Jason

>
> Thanks for your help,
> Alex
>
>
>
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