Thanks a lot Doug, We have followed your suggestion and now fMRI is the third sequence. Both patients and controls will have two sessions too.

Best

Daniel

----------------------------------------------------------------------

Message: 1
Date: Sat, 09 Nov 2013 12:50:39 -0500
From: Douglas Greve <greve@nmr.mgh.harvard.edu>
Subject: Re: [Freesurfer] acquisition in 1 session vs 2 sessions
To: freesurfer@nmr.mgh.harvard.edu
Message-ID: <527E75EF.2070807@nmr.mgh.harvard.edu>
Content-Type: text/plain; charset="iso-8859-1"


I think the only thing you would have to worry about is the fMRI since 
the way the subject reacts to the task (or state of subject during rest) 
might change depending upon how long he/she has been in the scanner. Why 
not do the fMRI at #3? Then each population would be in the scanner for 
the same amount of time. If the T1 and FLAIR are bandwidth matched, I'd 
do them in the same session. The only other confound could be that your 
controls might move more in the last couple of scans since they will 
have been in the scanner for a while at that point. Depending on your 
patient population, there might be difference in movement anyway. There 
should not be any problems with analyzing the data regardless of how you 
slice it up.

doug





On 11/9/13 3:56 AM, Daniel Ferreira wrote:

Dear experts,

We are designing a study including a long MR protocol:

1) Localizer
2) Cal
3) T1-FSPGR
4) FLAIR 3D
5) DTI 1
6) DTI 2
7) fMRI

Due to patients characteristics we were thinking on splitting the 
acquisition in two different sessions (session 1: sequences 1, 2, 3, 
4; session 2: sequences 1, 2, 5, 6, 7).

Do you think we should do the same for the healthy controls or we can 
scan them in just one single session? I wonder how system 
session-related artifacts could differentially affect the two kinds of 
protocol (spitted vs. single). I also wonder how FreeSurfer processing 
can be affected by this issues.

Thanks a lot.

Daniel Ferreira






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