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 <dani...@ull.es>
Date:01/31/2014 3:41 AM (GMT-05:00)
To: freesurfer@nmr.mgh.harvard.edu,mreu...@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,
1. 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).
2. 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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