With distinct fields/gradients and FS 4.01 I think you can have quite distinct results. My guess: 10% difference.
Bruce can give you a more accurate figure. At http://surfer.nmr.mgh.harvard.edu/fswiki/ReleaseNotes notice: "-norandomness is the the default. 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 -randomness flag can be used to allow usage of a random seed." I suggest you to upgrade to 4.5.0 cheers ---------------------------------------------------------- Pedro Paulo de M. Oliveira Junior Diretor de Operações Netfilter & SpeedComm Telecom -- For mobile: http://www.netfilter.com.br/mobile 2010/6/10 <bla...@artsci.wustl.edu> > One scanner is a Siemens Vision 1.5T and the other is a Siemens Trio 3T. > We used FreeSurfer 4.01 for the cross-sectional processing. > > Thanks, > > - Tyler > > > It's hard to know without the info about scanner type > > (Manufacturer/Field/Sequence) and FreeSurfer version. > > > > I usually see 3-5% difference in measurements. Phillips 3T with common > > fSPGR. > > ---------------------------------------------------------- > > Pedro Paulo de M. Oliveira Junior > > Diretor de Operações > > Netfilter & SpeedComm Telecom > > -- For mobile: http://www.netfilter.com.br/mobile > > > > > > > > > > On Thu, Jun 10, 2010 at 12:03, <bla...@artsci.wustl.edu> wrote: > > > >> Hi All, > >> > >> Our group recently scanned subjects with two different scanners in order > >> to determine how reliable FreeSurfer comparisons between the two > >> scanners > >> are. After putting each session through the regular cross-sectional > >> Freesurfer pipeline, we noticed that there is much greater variability > >> between the two scanners when we compare structures in the right > >> hemisphere than in the left. Is there any FreeSurfer related reason for > >> this? > >> > >> Also, we are currently running each subject through the longitudinal > >> pipeline (i.e. Scanner 1 as TP1, Scanner 2 as TP2). Is there any reason > >> to > >> think that this will help reduce the variability seen between the two > >> scanners? > >> > >> Thanks in advance for any help. > >> > >> - Tyler Blazey > >> > >> > >> > >> _______________________________________________ > >> Freesurfer mailing list > >> Freesurfer@nmr.mgh.harvard.edu > >> https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > >> > >> > >> The information in this e-mail is intended only for the person to whom > >> it > >> is > >> addressed. If you believe this e-mail was sent to you in error and the > >> e-mail > >> contains patient information, please contact the Partners Compliance > >> HelpLine at > >> http://www.partners.org/complianceline . If the e-mail was sent to you > >> in > >> error > >> but does not contain patient information, please contact the sender and > >> properly > >> dispose of the e-mail. > >> > >> > > > > >
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