If you do a text search on our wiki for "paired" it will take you to the instructions for doing a paired analysis.
doug Martin Reuter wrote: > Hi Brian, > > when you use the longitudinal stream in FreeSurfer, it accounts for the > 'relatedness' therefore the resulting information (e.g. segmentation > labels, volume measures, thickness measures, surface locations etc. ) > will be more accurate (on average) than if you'd just process the > different time points independently (cross sectionally). > > Comparing the results after FreeSurfer is through will work exactly the > same in both settings. You can compute what you are interested in (e.g. > percent volume loss in left hippocampus by looking into the aseg.stats , > or percent cortical thinning) per subject and then do a group analysis > with your two groups. > > Best, Martin > > > On Thu, 2009-10-01 at 14:39 -0400, Gogtay, Nitin (NIH/NIMH) [E] wrote: > >> Hi Martin + others, >> >> Thank you for your help on this. >> >> I am still a bit confused and maybe you can help me understand. So we have >> a sample of 12 patients + 12 controls and each with 2 scans (time 1 and time >> 2) thus total 48 scans. >> >> As suggested these have been processed using the longitudinal free surfer >> algorithm (Thanks for your help regarding troubleshooting during that as >> well) >> >> To compare the results between two time points (I assume slopes of subjects >> compared to those of controls? And intercepts?), how does one account for >> the 'relatedness' i.e. Same subject two time points? As it is now, wouldn't >> the free surfer treat the data as 'cross sectional' to calculate the slopes? >> >> Maybe i/we are missing something? >> >> Sorry for the bother and thank you again for the help! >> >> Nitin >> >> Nitin Gogtay, M.D. >> Staff Clinician >> Child Psychiatry Branch, NIMH >> (301) 435 4494 >> >> ________________________________ >> From: "Weisinger, Brian (NIH/OD) [E]" <brian.weisin...@nih.gov> >> Date: Thu, 1 Oct 2009 14:26:23 -0400 >> To: Nitin Gogtay <gogt...@mail.nih.gov> >> Subject: FW: [Freesurfer] How to calculate differences using the >> longitudinal data >> >> >> ------ Forwarded Message >> From: Martin Reuter <mreu...@nmr.mgh.harvard.edu> >> Date: Wed, 30 Sep 2009 14:49:46 -0400 >> To: "Weisinger, Brian (NIH/OD) [E]" <brian.weisin...@nih.gov> >> Cc: "Freesurfer@nmr.mgh.harvard.edu" <Freesurfer@nmr.mgh.harvard.edu> >> Subject: Re: [Freesurfer] How to calculate differences using the >> longitudinal data >> >> Hi Brian, >> >> after the longitudinal runs are through you have directories >> tpN.long.base for each timepoint per subject. These contain the same >> structure as the cross sectionally processed results, however the values >> (e.g. thickness, volume etc. in the stat files) should be more >> accurate. >> >> You can compare these results between timepoints in the same way you >> would do that without the longitudinal stream. You just need to take the >> more accurate information in the .long. directories instead. >> >> Best, Martin >> >> On Tue, 2009-09-29 at 14:59 -0400, Weisinger, Brian (NIH/OD) [E] wrote: >> >>> I have run the longitudinal stream on the scans I need, but now I am not >>> sure what to use to compare the differences. >>> If someone could clarify this for me I would really appreciate it. >>> >>> Thanks >>> >>> _______________________________________________ >>> Freesurfer mailing list >>> Freesurfer@nmr.mgh.harvard.edu >>> https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer >>> >>> >>> >> >> ------ End of Forwarded Message >> >> >> >> > > _______________________________________________ > 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 In order to help us help you, please follow the steps in: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
