Ok, thanks Martin for your advice. Is good to have it in mind for long designs.
Best
Daniel
--- Daniel Ferreira NVS Department, Div of Clinical Geriatrics (Karolinska Institute, Sweden) Department of Clinical Neuroscience (Karolinska Institute, Sweden) daniferp@gmail.com | daniel.ferreira.padilla@ki.se
El 31/01/2014 13:18, Martin Reuter escribió:
Hi Daniel, I'd also include 24 month into both the processing and analysis. It is not really that we are trying to improve a registration here. We are trying to improve segmentation and surface placement of each time point. I'd aways use all data, except there are good reasons to drop (eg strong motion artifacts). Best Martin
Sent via my smartphone, please excuse brevity.
-------- Original message -------- From: Daniel Ferreira Date:01/31/2014 3:41 AM (GMT-05:00) To: freesurfer@nmr.mgh.harvard.edu,mreuter@nmr.mgh.harvard.edu Subject: Re: [Freesurfer] longitudinal processing, template and flags
Thanks Martin for your reply,
I am agree with you on point 1. What would you say in the case that we are interested in rates of decline from baseline to 12 months, but besides 6 months follow-up we also have 24 months?. Here I see more conceptual problems. In an hypothetical context of severe atrophy from 12 to 24 months, adding the 24 mo follow-up perhaps difficult registration more than improves it. What do you think?
Thanks a lot
Best
Daniel
Hi Daniel,
- yes. But why not include 6 month in your study if you have those
scans??? You will get much more reliable slope estimates with 3 time points compared to 2, so including that time point will not only help for the image processing part, but also in your statistics (you gain power).
- I am not familiar with the mprage flag and think it mainly affects
the normalization. If you are sure you need it, then also add it to the -base and -long runs, just to be safe.
best, Martin
On 01/29/2014 09:08 AM, Daniel Ferreira wrote:
Dear experts,
I have two questions regarding the longitudinal stream:
- I am including Baseline and 12 months follow-up in my study.
However, I also have 6 months follow-up. I wonder if it is conceptually right to include these 6 months scans in template creation with the idea of increasing registration.
- I am applying the -mprage flag in the crossectional first step.
Should I use it in the -base and -longs steps too?
Thanks very much
Daniel Ferreira
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