p.s. I should add that we've known about this effect for a while (as the
authors in the paper state), but haven't had the time to track it down.
Since it's an avoidable source of variance (by controlling what computers
you run the analysis on), it's lower on our list of priorities than other
improvements. As far as the other part of the paper comparing different
versions I'll admit I'm puzzled as to why anyone would find it surprising
that different versions yield different answers. Would you want an MRI
analysis package to be the same in 2012 as in 1999? We're always trying to
improve things - increase accuracy and remove unecessary sources of
variance - so inevitably different versions give different results.
In any case, it's nice to get some posititive feedback :)
Bruce
On Wed, 20 Jun 2012, Peter J. Molfese wrote:
We run things on an Xgrid cluster that is now a mixture of Macs running Snow
Leopard (10.6.8) and Lion (10.7.x). We found the results given from
asegstats2table and aparcstats2table are identical after running 100
subjects on both Mac OS X 10.7.4 and 10.6.8 with Freesurfer 5.1. I also ran
a few subjects on the cluster and on individual computers (not on the
cluster so to speak) and the results are identical.
Best,
Peter
Hi,
The paper entitled
?The Effects of FreeSurfer Version, Workstation Type,
and Macintosh Operating System Version on Anatomical
Volume and Cortical Thickness Measurements?,
PLoSONE, Vol 7(6), e38234 (2012)
may be of interest to all of you. It can be found at:
http://dx.plos.org/10.1371/journal.pone.0038234
Cheers,
Ed
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