Hi Bruce,

Thanks for your quick response! So I have several follow-up questions:

1. As I load the two files (.sphere and .sphere.reg), there are two variables for each file, i.e. coordinates and facets. If I want to measure the distortion during registration, I will only need to look at coordinates? If so, the most appropriate way is simply calculating the Euclidean distance for each vertex between the two files (i.e., compute the distance between the first row of coordinates in .sphere file and the first row of coordinates in .sphere.reg, and so forth)?

2. What file I can use to get the distortion by the sphere inflation, as you mentioned?

3. The measure of vertex-wise distortion is basically how far each vertex has been warped from its original coordinate (native space) to the new coordinate (fsaverage space)? Thanks!

Best,

Tony

From: freesurfer-bounces@nmr.mgh.harvard.edu <freesurfer-bounces@nmr.mgh.harvard.edu> on behalf of Bruce Fischl <fischl@nmr.mgh.harvard.edu>
Sent: Thursday, November 9, 2017 12:28:13 PM
To: Freesurfer support list
Subject: Re: [Freesurfer] comparing sphere and sphere.reg

Hi Tony

you can do that but it won't measure the distortion induced by the sphere
mapping itself.

cheers
Bruce

On Thu, 9 Nov 2017, tony han wrote:

>
> Hi,
>
>
> I'm trying evaluating the distortion for each subject from their native space to fsaverage atlas
> space. Is it a appropriate measure to compare ?h.sphere and ?h.sphere.reg? I assume that by
> comparison, I may get the how each vertex warped during the registration? Thanks!
>
>
> Best,
>
> Tony
>
>
>
>