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Does this help
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?
On 5/15/2023 4:18 PM, Silberfeld, Andrew wrote:
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Hello FS Community,
I'm working on a study about left-right asymmetry and one of the
experiments I'd like to do is to directly compare the average percent
change between sides for each ROI when processed using a volumetric
registration and when processed using FreeSurfer's surface-based
approaches (same set of images). I'm hoping to characterize the degree
to which both software produce consistent patterns of LR asymmetry for
volume. However, I'm not sure what the best way is to implement a
symmetrical registration with ROIs in FreeSurfer and I'm wondering
what is recommended?
For starters, the DK atlas/template is not feasible due to its
inherent asymmetry, andI've considered a number of approaches but it
feels like a challenge prohibits each one. What is the best way to go
about doing this?
I've considered the following ideas:
1. (Most ideally) I could import my already obtained symmetrical
volumetric template/atlas into FreeSurfer, but my understanding is
that making the .gca file requires multiple annotated subjects
rather than a single annotated atlas, since FS uses probabilistic
segmentations.
2. I've looked at the xhemi approach from Greve et al. 2013 but my
impression from reading the documentation is that this gives
results that differ based on whether the left hemisphere or right
hemisphere is used and also that the final results are described
for each vertex, rather than for each parcel which I need
(although the original paper did do some ROI-analysis).
3. I've also thought about performing recon-all on each sample twice:
once in the proper orientation and once more after flipping the LR
orientation of each sample. From there I could compare the left
hemi and the flipped-right hemi to each other which I think avoids
the DK atlas bias. This feels similar to option 2 and so I'm not
sure if this would give results that vary based on which
hemisphere is used for analysis. Also the documentation says I
would need to manually change lines in the text file, which is not
an ideal solution for several hundred subjects, although this
could be scripted. (*MailScanner has detected a possible fraud
attempt from "secure-web.cisco.com" claiming to be*
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<https://secure-web.cisco.com/1b40CbQ8lToemytkQqJc49_lPSzSyb_qOkrmyKts2VtGlgwJ5dD2cuI0nnd3FAn_YLHaAkF8Ob7ueYWA6Y1-LVFB0gwBaWXyc3Sk1TX_WFlYGA2uHUNicZ3moan43Me7J16G0dSePnbrVCH285NOldL_stK1Z5lTVJu8nO7bLiC7RVHLkMWUDMCGBVYSaDx6TuRnb_sNv8NMyer4uedYY7fpucl2dWvnUuVgztPVO2-QV6f0zy7RMcNPK7mvB9plgvy6NOjo80GRKhrLsF474p2MyyhVSZvzEDgA9htKEqTybiZNVSW9-pyRpcA0s5D08wImAk_StC4IXMTjARO4TUg/https%3A%2F%2Fsurfer.nmr.mgh.harvard.edu%2Ffswiki%2FLeftRightReversal>).
Maybe I'm overthinking it. What is the best way to go about doing this?
Thank you,
Andrew
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