This is tough to interpret, but basically, yes it would be 0-.004mm2/year. It is not quite right to say that it is at that vertex because of smoothing, but in that area. It is also hard to say what the total change would be for a cluster. One could sum the changes over the cluster vertices, but that would probably over-estimate the change. doug
On 09/06/2014 09:51 AM, Lars M. Rimol wrote: > > Hi, > > I have performed a longitudinal analysis using the lme module in > FreeSurfer, with this model: > > *intercept(random effect) + centered age + group + group x centered > age + sex* > > I tested the effect of time with this contrast vector [ 0 1 0 0 0 ]. > Dependent variable is area. > > Here, mapping the second beta means mapping the effect size for > (change over) time. In the beta map, I find values from 0 to 0.004. I > would interpret that to mean that local area shrinks by at most 0.004 > mm² per year in the reference group. But I'm not 100% sure about the > biological (or geometrical) meaning of that. > > Can I interpret this literally as the mean yearly shrinkage of the > three triangles surrounding a given vertex, the average of whose area > comprises the area score of the vertex, being 4/1000 mm? Of course, > these maps are smoothed with 30mm, so the real spatial resolution is > nowhere near this.... > > > Thank you! > > > -- > yours, > > Lars M. Rimol, PhD > St. Olavs Hospital > Trondheim, > Norway > > > _______________________________________________ > Freesurfer mailing list > Freesurfer@nmr.mgh.harvard.edu > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer -- Douglas N. Greve, Ph.D. MGH-NMR Center gr...@nmr.mgh.harvard.edu Phone Number: 617-724-2358 Fax: 617-726-7422 Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting FileDrop: https://gate.nmr.mgh.harvard.edu/filedrop2 www.nmr.mgh.harvard.edu/facility/filedrop/index.html Outgoing: ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/ _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer The information in this e-mail is intended only for the person to whom it is addressed. If you believe this e-mail was sent to you in error and the e-mail contains patient information, please contact the Partners Compliance HelpLine at http://www.partners.org/complianceline . If the e-mail was sent to you in error but does not contain patient information, please contact the sender and properly dispose of the e-mail.
