instead of changing the average you can generate a registration with less
distortion by for example invoking mris_register with -dist 1 to increase
the penalty on the metric distortion term
On Thu, 20 Sep 2007, Jiefeng Jiang
wrote:
Sorry that I did not make it claer. The resampling did not fail, just the
result was not good.
The resamping process is like this:
I treated reconstructed cortical surfaces as functions defined on a sphere.
Meanwhile, I divided a sphere into 163842 points and 300,000+ triangles by
iteratively subdividing a icosahedron for 7 times. I would like to compute the
spatial coordinates of the 163842 points in R^3 space and then get a resampled
cortical surface. To achieve this, I linearly interpolated the 163842 points on
the ?h.sphere.reg files and computed their spatial positions.
The problem is that after spherical registration, the triangles on
?h.sphere.reg became more unevenly distributed(or distorted) -- some of them
had very small areas. Thus the 163842 points which were evenly spread on the
sphere may not resample all the details of the cortical surface. In my case,
some resampled triangles were too large that some sulci disappeared. I hope
that changing the default average surface of mris_register may fix the
problem...
Thanks.
----- Original Message -----
From: "Bruce Fischl" <[EMAIL PROTECTED]>
To: "Jiefeng Jiang" <[EMAIL PROTECTED]>
Cc: <freesurfer@nmr.mgh.harvard.edu>
Sent: Thursday, September 20, 2007 7:45 PM
Subject: Re: [Freesurfer] Average surface of mris_register
I'm sorry, I don't understand. What resampling fails? How does it fail?
On
Thu, 20 Sep 2007, Jiefeng Jiang wrote:
Hi,
I am using the ?h.sphere.reg files automatically generated by reconall. However, I found
that the area distortion compromise the results of my following resample step. I wonder
whether replacing the default average surface
"$FREESURFER_HOME/average/?h.average.curvature.filled.buckner40.tif" with the
?h.sphere in the /average/surf directory would reduce the distortion. If so, could anyone
tell me how to get a .tif file using files in /average/surf directory?
Thank you!
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