External Email - Use Caution
Hello,
I am running a dataset through version 6.0 of Freesurfer on Linux,
extracting results for both the Desikan atlas and our own atlas. When
extracting the stats for our atlas, the results were varying considerably
(sometimes up to 10%) in test-retest runs.
The release notes for 4.5 indicate that the default setting for
mris_ca_label should use the same number as a seed, and therefore give the
same results, but it doesn't.
"The binaries in the recon-all stream which are subject to variability due
to usage of a random number generator (mris_smooth, mris_sphere,
mris_topology_fixer, mris_topo_fixer and mris_ca_label) are now seeded with
the same number, with the result being that repeated runs of the recon-all
stream on a subject on the same platform will always give identical
results."
The issue seems to be resolved by adding -seed 1234 as a flag to
mris_ca_label.
I would like to understand what this is actually doing though, before
applying it to all my data. What is the random number generator used for?
What does setting it to 1234 actually do? It isn't listed in the optional
flagged arguments. Is it just deciding which vertex is labeled first?
Here is how we are running it (in two independent scripts):
FIRST:
# autorecon1 including data conversion
recon-all -i $mprage/001 -autorecon1 -subjid $s
# autorecon2 with threshold adjustments
recon-all -seg-wlo 60 -seg-ghi 70 -autorecon2 -subjid $s
# autorecon3
recon-all -autorecon3 -subjid $s
THEN:
mris_ca_label $s $h sphere.reg
/g5/dcn/freesurfer_testing/subjects/"$h".rantaFL.gcs
rantaFL.annot
modified to:
mris_ca_label -seed 1234 $s $h sphere.reg
/g5/dcn/freesurfer_testing/subjects/"$h".rantaFL.gcs
rantaFL.annot
Thank you,
Rosemary Nicholas
Center for Neurodevelopmental and Imaging Research
Kennedy Krieger Institute