Dear Martin and FS experts, I have a small follow-up question regarding the post below. Given a young sample where ICV is still growing, that I want to control for this and that the data look ok: Can I use the cross-sectional ICV as a covariate in analyses on the longitudinal data? Or will this introduce any bias?
In other words, does “the longitudinal stream assumes head size is fixed across time” affect the estimated long values when this assumption is incorrect? Best regards, Christian K Tamnes ________________________________________ From: freesurfer-boun...@nmr.mgh.harvard.edu <freesurfer-boun...@nmr.mgh.harvard.edu> on behalf of Martin Reuter <mreu...@nmr.mgh.harvard.edu> Sent: 14 October 2014 17:23 To: Freesurfer support list Subject: Re: [Freesurfer] ICV for adolescent and young adult in longitudinal stream Hi Knut, the longitudinal stream assumes head size is fixed across time. That is why we report only one ICV (the one from the within subject template) in all time points. If in your data heads are growing still, you can still use the longitudinal stream, but need to be carefully inspecting your data (e.g. are surfaces OK in both time points, is the skull strip good etc). You can also read out the individual ICV on each time point when looking at the cross sectional directories (first step of the long pipeline), there in aseg. stats are the ICV's for each time point. Best, Martin On 10/13/2014 12:24 PM, Knut J Bjuland wrote: > Dear FreeSurfer export, > > I have used the longitudinal stream in FreeSurfer. However, when I > extracted the ICV for adolescents and young adult, I get the same number > for those subjects that are present at two-time points. Will > registration to a common space cause the change in ICV? Can this change > explain why the icv is equal at 15 and 19 years of age for all my > subjects with two-time points? > > > Best regards, > > Knut Jørgen Bjuland > PhD candidate > NTNU > Trondheim > > > > _______________________________________________ > Freesurfer mailing list > Freesurfer@nmr.mgh.harvard.edu > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > -- Dr. Martin Reuter Instructor in Neurology Harvard Medical School Assistant in Neuroscience Dept. of Radiology, Massachusetts General Hospital Dept. of Neurology, Massachusetts General Hospital Research Affiliate Computer Science and Artificial Intelligence Lab, Dept. of Electrical Engineering and Computer Science, Massachusetts Institute of Technology A.A.Martinos Center for Biomedical Imaging 149 Thirteenth Street, Suite 2301 Charlestown, MA 02129 Phone: +1-617-724-5652 Email: mreu...@nmr.mgh.harvard.edu reu...@mit.edu Web : http://reuter.mit.edu _______________________________________________ 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
