Hi Yang,

To edit the pial surface, you want to use brainmask.mgz.

As for the wm.mgz, you're right in that control points isn't the solution. 
Control points are to fix intensity problem, but you can also add wm 
voxels manually to fix any wm defects. In this case, adding that many control 
points 
would probably make the situation worse because the entire area will 
brighten and that would potentially extend the surfaces to include grey 
matter.

Is the area you pointed out by any chance the ventricle? If it is, then it 
doesn't matter that the white surface includes it. It's hard 
to tell with just this image. Do you mind sending a snapshot of the 
brainmask.mgz for this slice?

On Mon, 10 Jan 2011, Yang Liu wrote:

> Hi Freesurferers,
>
> I am correcting some defects in the white matter surface (yellow) and the
> pial surfaces (red). But I am not very sure of which volume I should work
> on.
> I did several experiments on editing one volume at a time.
>
> For pial (the red) surface, I edited brain.mgz first. I found it corrected
> some pial defects.
> However, I found one previous post here said the volume that should be
> edited is brainmask.mgz.
> So the second time I only changed brainmask.mgz. It also works.
>
> So, which one should I work on?
>
> brian.mgz or brainmask.mgz?
>
> Also, for defects on the white matter surface (the yellow one),  I found the
> surface doesn't follow the white matter segmentation closely, although I
> have a good wm.mgz. (see attached image).
> At the location pointed by the red arrow in the attached image, both the
> green and yellow sufaces includes a lot of gray matter at the location. It
> is strange that the wm.mgz has a very well defined slice in that
> neighborhood.
> I am familiar with situations where the surfaces miss a few white matter
> pixels, for which I can add a few control points to improve it.
>
> How shall I edit wm.mgz to correct this?  Adding more control points is not
> a solution, apparently.
>
> Thank you.
>
> Yang
>
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