Hi Enrica,

surfaces are placed in 3D between voxles and so even in the cross sectional stream they can detect sub-mm differences in e.g. thickness. The longitudinal stream increases reliability as it deforms the same surface model to each of the time points within a subject instead of re-creating surfaces from scratch.

Some papers related to that are:

http://www.nmr.mgh.harvard.edu/~fischl/reprints/Han_NeuroImage_2006_thickness_reliability.pdf
Reliability of MRI-derived measurements of human cerebral cortical thickness: The effects of field strength, scanner upgrade and manufacturer, X. Han, J. Jovichich, D. Salat, A. van der Kouwe, B. Quinn, S. Czanner, E. Busa, J. Pacheco, M. Albert, R. Killiany, P. Maguire, D. Rosas, N. Makris, A. Dale, B. Dickerson, and B. Fischl, (2006) NeuroImage, 32(1):180-194.

and
http://reuter.mit.edu/papers/reuter-long12.pdf

Within-Subject Template Estimation for Unbiased Longitudinal Image Analysis, M. Reuter, N.J. Schmansky, H.D. Rosas, B. Fischl, (2012), NeuroImage 61(4):1402-1418.

Best, Martin

On 01/04/2016 12:07 PM, Enrica Cavedo wrote:

Dear Freesurfers,

I'm going to perform a longitudinal analysis of cortical thickness using 3D-T1 images with a voxel size of 1mm isotropic. Could you kindly explain the robustness of free surfer longitudinal pipeline to calculate sub-mm changes on the cortex.

thank you in advance for your help,

best regards,

enrica
_______________________________________________
Freesurfer mailing list
Freesurfer@nmr.mgh.harvard.edu
https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer

-- 
Martin Reuter, PhD
Assistant Professor of Radiology, Harvard Medical School
Assistant Professor of Neurology, Harvard Medical School
A.A.Martinos Center for Biomedical Imaging
Massachusetts General Hospital
Research Affiliate, CSAIL, MIT
Phone: +1-617-724-5652
Web  : http://reuter.mit.edu