At 2017-03-22 21:58:12, "Bruce Fischl" <fischl@nmr.mgh.harvard.edu> wrote:
>Hi Hui
>
>meancurv is the spatially smoothed mean curvature of the surface at each 
>point (that is, the average of the two curvatures k1 and k2)
>
>cheers
>Bruce
>On Wed, 22 Mar 
>2017, Àî»Û wrote:
>
>> Dear FreeSurfer Group,
>> 
>> Sorry for interrupting.
>> 
>> I am Hui Li, a researcher fron Beijing, China, interesting in sMRI of mind
>> disorder. Recently, I am working on some data about schizophrenia. I
>> compared the patients and healthy controls, and found that the main
>> difference between these two groups is the index of "meancurv". So I
>> searched online for the papers described "meancurv" of using FreeSurfer
>> package, however, most of the papers reported an index---gyrificaiton, some
>> of the gyrificaiton was calculated from "absoult mean curvatura", for
>> example articles from Dr. Luders (A curvature-based approach to estimate
>> local gyrification on the cortical surface, NeuroImage, 2006, 29, 1224).
>> Then I looked for how to calculate "meancurv" in FreeSurfer, I found that
>> "The curvature in general is measured as 1/r, where r is the radius of an
>> inscribed circle. Since mean curvature is the average of the two principal
>> curvatures it has the units of 1/mm. The Gaussian curvature is the product
>> of them, so it is 1/mm^2". I am confused about these two concepts of "mean
>> curvatura", could you help me to understand the "mean curvatura" in
>> FreeSurfer? What is the biological meaning of this index, does it share the
>> same anatomical meaning with Dr. Luders'? Could I use "mean curvatura" from
>> FreeSurfer represent Gyrification Index?
>> 
>> Thanks all of you so much.
>> 
>> Hui Li
>> 
>> 
>> 
>>  
>> 
>> 
>>