By the way, smoothing can remove the thickening (if there is only a little and mainly thinning ).
Best, Martin
On 08/05/2013 02:18 PM, Martin Reuter wrote:
Hi Bastian,
actually (see other mail today) it computes percent thickening per year as it is the slope of the linear fit into the measurements (thickness with respect to age or time). If the slope is negative, there is thinning.
The results (within subject and on fsaverage) have signs so they always reflect both thinning or thickening. And usually due to noise you'll find regions in an individual subject that go both ways. So when you look at the within subject results (on the base anatomy) you should see both blue and red regions. that should be also true for when looking at the same map on fsaverage (it is just mapped there, should not change the sign, only the location a little).
Best, Martin
On 08/02/2013 05:31 AM, Bastian Cheng wrote:
Dear freesurfer-experts,
I have successfully done a longitudinal analysis on cortical thickness changes over 2 timepoints (0 and 1 year).
My question is:
If I look at the -individual- overlays of perc. change (i.e. pc1fit), only positive values are shown. whereas at the -fsaverage- view, positve AND negative values are shown (i.e. thinning and thickening)
I understood that long_mris_slopes calculates the "percent thinning per year". But is there a way to show both sides of the histogramm (i.e. from -2 to +2) also on the -individual- overlay?
This might be a naive question, however, any help is greatly appreciated!
Bastian. _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer