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 <mreu...@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: > mreu...@nmr.mgh.harvard.edu > reu...@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 > 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
