Hi Joana, actually it is possible, when using long_mris_slopes after running your longitudinal data (I think that is what you did).
I cannot judge if your table is correct. You did create that table from the longitudinal qdec table as described on the wiki (longitudinal tutorial) right? So each line should be a template/base name and in the longitudinal table there should be two entries for each of these templates. I notice that the years (here the average, so probably the distance in time between your two time points) differs a lot (half a year to a year) between subjects, that is of course not optimal. You can look at different things: difference per year (rate) percent change per year with respect to baseline (pc1) or percent change per year with respect to average thickness (spc, called symmetrized percent change as it is symmetric). If you are interested in the change per year, long_thickness_rate is correct. It accounts for the different time intervals. You can then (in qdec) check if this is measure is different from zero. So everything you describe looks good. Best, Martin On Fri, 2011-09-23 at 11:25 -0400, Douglas N Greve wrote: > This is actually something that you cannot currently do in QDEC. Try > doing a search for "paired" on our wiki for instructions on how to do > this type of analysis. > doug > > Joana Braga Pereira wrote: > > Dear Freesurfers, > > > > I'm doing a longitudinal analysis of cortical thickness using the > > newest version of Freesurfer and there is something i would like to > > ask you all. > > > > I have two time points and only one group of patients. > > > > I've finished the pre-processing and am now searching for differences > > between the two time points using Qdec. > > > > Since i only have one group my cross.qdec.table.dat file looks pretty > > much like this: > > > > fsid years > > template_M_b01 0.665 > > template_M_b02 0.665 > > template_b03 0.71 > > template_b04 0.79 > > template_b05 0.915 > > template_b07 0.665 > > template_b09 0.625 > > template_b10 0.625 > > template_b11 0.71 > > template_b13 1.04 > > template_b14 0.71 > > template_b15 0.665 > > template_b16 0.835 > > template_b17 0.665 > > template_b18 0.625 > > template_M_b19 0.71 > > template_M_b20 0.625 > > template_b21 0.71 > > template_b22 0.585 > > > > I selected the long.thickness.rate in Qdec interface and years as > > continuous covariate since it is the only variable that i have in > > my cross.qdec.table.dat (no groups or other covariates of interest). > > > > My question is: Is this the analysis i should be doing given that i > > want to know the differences between time point 1 - time point 2? > > > > Many thanks, > > > > Joana > > ------------------------------------------------------------------------ > > > > _______________________________________________ > > Freesurfer mailing list > > Freesurfer@nmr.mgh.harvard.edu > > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > _______________________________________________ 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.
