Ok, but my automatic procedure constructed the ROI
masks on the lh.sphere (not on lh.sphere.reg)of the
fsaverage subject.
Is it wrong to compute the area of a ROI in the
fsaverage spherical surface by adding the areas of the
triangular faces inside this region? (The area of each
triangular face being computed using the spherical
coordinates of its vertices and the Heron formula for
the triangle area)
Thank you for your useful help
Jorge
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Hi Jorge,
the ?h.sphere is the metrically optimal surface, but after spherical
registration, the ?h.sphere.reg has a fair amount of metric distortion,
which is necessary to align folds
cheers,
Bruce
On Wed, 12 Sep 2007, jorge luis wrote:
Hello all
I have made changes in the thickness values in some
regions of a left hemisfere of a subject surface after
mapped it onto the fsaverage sphere.
The changes were made to have areas close to these in
the left colum of the following table:
My area Freesurfer number of vertices
20 mm2 27.88 mm2 (37)
30 mm2 35.09 mm2 (47)
40 mm2 39.17 mm2 (52)
50 mm2 56.89 mm2 (76)
60 mm2 44.05 mm2 (59)
I computed the region areas in the fsaverage surface
by adding the areas of the triangular faces inside
these regions using the spherical coordinates of the
vertices and the Heron formula for the triangle area.
The freesurfer sphere mapping is based in minimal
metric distortion, so, why the freesurfer computed
areas for these regions are different(the second
column in the table)?
In both cases the same surface vertices were found
to be inside of the regions (the third column in the
table)
I would like to have more insight on how freesurfer
compute the area of a given ROI in the fsaverage
spherical surface.
In advance thank you
____________________________________________________________________________________
Sé un Mejor Amante del Cine
¿Quieres saber cómo? ¡Deja que otras personas te ayuden!
http://advision.webevents.yahoo.com/reto/entretenimiento.html
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