Hi Joana, no, what you did is fine. I just wanted to make sure that you are using the cross table created from the long table (so that there is only a single entry for each subject). It looks like that is the case.
Best, Martin On Tue, 2011-09-27 at 12:11 +0200, Joana Braga Pereira wrote: > Hi Martin, > > > Many thanks for your reply! > > > I did follow all the steps as described in the wiki. > > > I'm not sure i understand your suggestion though.. > > > Are you proposing that, instead of using the cross.qdec.table, i > should use the longitudinal table to see the difference between two > time points? > > > My long.qdec.table looks like this: > > > fsid fsid-base years > M_b01_pre template_M_b01 0 > M_b01_post template_M_b01 1.33 > M_b02_pre template_M_b02 0 > M_b02_post template_M_b02 1.33 > M_b03_pre template_b03 0 > M_b03_post template_b03 1.42 > M_b04_pre template_b04 0 > M_b04_post template_b04 1.58 > M_b05_pre template_b05 0 > M_b05_post template_b05 1.83 > M_b07_pre template_b07 0 > M_b07_post template_b07 1.33 > M_b09_pre template_b09 0 > M_b09_post template_b09 1.25 > M_b10_pre template_b10 0 > M_b10_post template_b10 1.25 > M_b11_pre template_b11 0 > M_b11_post template_b11 1.42 > M_b13_pre template_b13 0 > M_b13_post template_b13 2.08 > M_b14_pre template_b14 0 > M_b14_post template_b14 1.42 > M_b15_pre template_b15 0 > M_b15_post template_b15 1.33 > M_b16_pre template_b16 0 > M_b16_post template_b16 1.67 > M_b17_pre template_b17 0 > M_b17_post template_b17 1.33 > M_b18_pre template_b18 0 > M_b18_post template_b18 1.25 > M_b19_pre template_M_b19 0 > M_b19_post template_M_b19 1.42 > M_b20_pre template_M_b20 0 > M_b20_post template_M_b20 1.25 > M_b21_pre template_b21 0 > M_b21_post template_b21 1.42 > M_b22_pre template_b22 0 > M_b22_post template_b22 1.17 > > > If i did that, qdec won't find long.thickness-rate...This measure as > well as the other longitudinal measures (pc1, spc, etc) can only be > found in the surf subfolders of the templates (fsid-base). > > > What did i miss? > > > Thanks for your patience, > > > Joana > > > > > > 2011/9/23 Martin Reuter <mreu...@nmr.mgh.harvard.edu> > 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 > > > > > > > > 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. > > > > _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
