Hi Lee
It's really hard to say. The change in voxel size might sound trivial, but it
is a 30% change in volume (and hence SNR). The longer TE will counteract that
by increasing T2* weighting.
Sorry I don't have anything more conclusive to say except that it is obviously
not ideal
Bruce
From: freesurfer-boun...@nmr.mgh.harvard.edu
<freesurfer-boun...@nmr.mgh.harvard.edu> On Behalf Of Backhausen, Lea
Sent: Thursday, November 5, 2020 12:13 PM
To: 'freesurfer@nmr.mgh.harvard.edu' <freesurfer@nmr.mgh.harvard.edu>
Subject: [Freesurfer] Different Sequences Longitudinal Stream {Disarmed}
External Email - Use Caution
Dear FreeSurfer experts,
I am currently working on a longitudinal data set with 4 time points, acquired
at one site with the same Siemens Trio 3T scanner.
Unfourtunately, the T1 sequence differs slightly for one of these time points.
These sequences have been measured:
1. repetition time (TR) = 2300 ms, echo time (TE) = 2.93 ms, inversion time
(TI) = 900 ms, voxel size = 1.1 x 1.1 x 1.1mm, flip angle = 9°; matrix size =
256 x 256 x 160 mm
2. repetition time (TR) = 1900 ms, echo time (TE) = 2.26 ms, inversion time
(TI) = 900 ms, voxel size = 1.0 x 1.0 x 1.0mm, flip angle = 9°; matrix size =
256 x 256 x 176 mm
Is it possible to process these different sequences in the longitudinal stream
(if e.g. one participant would have 3 data sets of sequence 1 and one data set
of sequence 2)?
Or would this cause too much bias?
Thank you very much, kind regards!
Lea Backhausen
------------------------------
Lea Backhausen
Ph.D. Student (M.Sc. Psychology/Neuroscience)
Department of Child and Adolescent Psychiatry, Faculty of Medicine of the TU
Dresden, Germany
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