Hi Martin,
Thank you for your answer, but my idea was to compare the atrophy
rates when using scans at 6 months (0 - 6 months) and scans at 12
months (0 - 12 months). If my templates are built with more time
points, the results will be biased, right?
Regards,
Yolanda
2013/3/18 Martin Reuter <mreuter@nmr.mgh.harvard.edu>:Hi Yolanda,
actually it is advantageous if the template is build from more time points.
You don't need to process the images again, just do your statistical
analysis with the time points you are interested in.
But: why restrict the statistics to a subset of the data? If you are
interested in yearly change, you can compute that from all time points. If
you are interested in seeing if the atrophy rate increases over time, use a
piecewise linear model (node at 6 months) and see if the slopes increase,
etc. Removing time points from the statistics is usually a bad idea as you
loose power.
Best, Martin
On 03/18/2013 01:15 PM, Yolanda Vives wrote:
Dear FreeSurfer experts,
I have run a longitudinal study considering multiple time points (7
scans/subject on average) with FS 5.1. However, I am interested in the
percent changes between two time points only (between 0 and 6 months
and between 0 and 1 year). Should I run the longitudinal stream from
step 2 (template) two more times (1.- considering only 0 and 6 months
scans and 2.- considering only 0 and 12 months scans) or is it correct
even if my templates were built with all the time scans together?
Thank you for your help,
Yolanda
_______________________________________________
Freesurfer mailing list
Freesurfer@nmr.mgh.harvard.edu
https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
--
Dr. Martin Reuter
Assistant in Neuroscience - Massachusetts General Hospital
Instructor in Neurology - Harvard Medical School
MGH / HMS / MIT
A.A.Martinos Center for Biomedical Imaging
149 Thirteenth Street, Suite 2301
Charlestown, MA 02129
Phone: +1-617-724-5652
Email:
mreuter@nmr.mgh.harvard.edu
reuter@mit.edu
Web : http://reuter.mit.edu
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
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.