Dear Bruce Fischl
?h.white.H, ?h.curv, and H Mean reflected the vector fields with 'sign(+ or -)', and MeanCurv reflected the integral of the 'absolute' value of mean curvature. Am I understanding this correctly?
Best Wishes,
Han
On Mon, Oct 3, 2016 at 7:49 AM, Bruce Fischl fischl@nmr.mgh.harvard.edu wrote:
Hi Han
I'm not sure I understand you question. The sign of the curvature depends on the arbirary convention you choose for the normal vector field over the surface. We pick and outwards pointing normal, which means that gyral regions in general have negative curvature (since they lie 'below' the tangent plane in terms of their dot product with the normal) and sulcal ones are positive. AFAIK both the ?h.white.H and ?h.curv curvatures obey this convention, although the smoothing applied to the ?h.curv will mean that some places they will have different sign. If you plot them both you will see that they are pretty highly correlated though.
Does that answer your question? If not, can you clarify?
cheers Bruce
On Sun, 2 Oct 2016, Hanbyul Cho wrote:
Dear FreeSurfer Team,
I apologize for the repetitive questions.
I made 2 labels which included bilateral paracentral lobule and sulcus regions. Then I extract the values:
- MeanCurv After mris_anatomical_stats processing, I extracted the MeanCurv by
the command, 'aparcstats2table --hemi ?h --parc <label> --meas meancurv --subjects <subjects list> --tablefile <output.txt>'
- ?h.Curv After mris_anatomical_stats processing with the option '-t
lh.curv', I extracted the curvature value by the command, 'aparcstats2table --hemi ?h --parc <label> --meas thickness--subjects <subjects list> --tablefile <output.txt>'
- H <mean> +- <std>, H Mean Rectified Surface Integral The Mean curvature values were compute by the command, 'mris_curvature_Stats -l <label> -g -n -m -f white -o <output.txt>
<subject> ?h'
I analyzed the each value. The ?h.Curv mean (within the label) has opposite relationship with Z value compared to MeanCurv, while similar relationship with Z value compared to H <mean>.
I heard that the MeanCurv is the integral of the rectified mean curvature of white matter surface (1/r mm), and ?h.curv is the mean curvature of the white matter surface with a Gaussian smoothing kernel applied. It looks that the MeanCurv and H Mean Rectified Surface Integral has only positive values, while the H <mean> and ?h.curv has positive or negative value.
I wonder whether MeanCurv and ?h.curv has the difference meaning or difference formula. And I would like to know the meaning of the ?h.curv negative value. Is H <mean> ( by mris_curvature_Stats ) compute from ?h.curv ?
Thank you.
Han.
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