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Dear Freesurfer Developers,
It is not clear to me how to calculate the Euler number. Using mri_segstats reports something like: Computing euler number orig.nofix lheno = -18, rheno = -20 orig.nofix lhholes = 10, rhholes = 11 However, I had understood from previous comments that the Euler number should be around 2. I'm wondering which of the above numbers I could report.
Thanks, Colleen
Hi Colleen
After correction the Euler number should be exactly 2. If it is not, it means the surface is not topologically equivalent to a sphere. Every defect (hole or handle) will decrease it by 2, so an Euler number of -18 (like your lh below) is:
# of holes = (2-euler_number)/2 = (2--18)/2 = 10
Make sense?
Cheers Bruce
-----Original Message----- From: freesurfer-bounces@nmr.mgh.harvard.edu freesurfer-bounces@nmr.mgh.harvard.edu On Behalf Of C.P.E. Rollins Sent: Thursday, September 3, 2020 12:17 PM To: Freesurfer freesurfer@nmr.mgh.harvard.edu Subject: [Freesurfer] how to calculate Euler number
External Email - Use Caution
Dear Freesurfer Developers,
It is not clear to me how to calculate the Euler number. Using mri_segstats reports something like: Computing euler number orig.nofix lheno = -18, rheno = -20 orig.nofix lhholes = 10, rhholes = 11 However, I had understood from previous comments that the Euler number should be around 2. I'm wondering which of the above numbers I could report.
Thanks, Colleen
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Thanks for the clarification Bruce. Would it make sense then to report -18 ? As suggested by the Rosen 2018 paper in Neuroimage.
Thanks again, Colleen
On 2020-09-03 17:16, C.P.E. Rollins wrote:
Dear Freesurfer Developers,
It is not clear to me how to calculate the Euler number. Using mri_segstats reports something like: Computing euler number orig.nofix lheno = -18, rheno = -20 orig.nofix lhholes = 10, rhholes = 11 However, I had understood from previous comments that the Euler number should be around 2. I'm wondering which of the above numbers I could report.
Thanks, Colleen
I guess that makes sense
-----Original Message----- From: freesurfer-bounces@nmr.mgh.harvard.edu freesurfer-bounces@nmr.mgh.harvard.edu On Behalf Of C.P.E. Rollins Sent: Thursday, September 3, 2020 12:48 PM To: Freesurfer freesurfer@nmr.mgh.harvard.edu Subject: Re: [Freesurfer] how to calculate Euler number
External Email - Use Caution
Thanks for the clarification Bruce. Would it make sense then to report -18 ? As suggested by the Rosen 2018 paper in Neuroimage.
Thanks again, Colleen
On 2020-09-03 17:16, C.P.E. Rollins wrote:
Dear Freesurfer Developers,
It is not clear to me how to calculate the Euler number. Using mri_segstats reports something like: Computing euler number orig.nofix lheno = -18, rheno = -20 orig.nofix lhholes = 10, rhholes = 11 However, I had understood from previous comments that the Euler number should be around 2. I'm wondering which of the above numbers I could report.
Thanks, Colleen
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