Freesurfer October 2007

freesurfer@nmr.mgh.harvard.edu

55 participants
79 discussions

intrasubject segmentation variance
by Thomas Doering 22 Oct '07

22 Oct '07

Dear freesurfers, i was running Freesurfer on the same subject on two independent Computers. The first Computer PC1has 2 physical Intel processors with 2 logical each - (dual core) - 1.6GHz with 4Gb Ram and the second PC2 has 2 physical Intel processors with 4 logical - (quad core) - 3 GHz with 8 Gb Ram. After running on these two Computers - i start at the exactly same time - i got a surprising result: My faster Computer PC2 took 41h to run the subject and the slower Computer took 31h. I wonder if somebody have some comment on this, because i have no idea what is wrong ( When i have the Linux System Monitor on, watching the CPU History, it seems that the slower PC hat a more effective occupation/usage than the faster - switching faster between one CPU and the other one...) Another small question: In the final segmentation table, i noticed that there are some small diferences between the results of PC1 and PC2: for ex.: PC1:ctx - rh-caudalmiddle frontal = 5029 5029 PC2:ctx - -"- 5360 5360 , so a diference of ~6%. I guess these are variations due to the algorithm.. Are there some established limits for that diferences? Thanks for help, Thomas

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About tissue probability maps from aseg.mgz
by Burak Ozkalayci 22 Oct '07

22 Oct '07

Dear surfers, I want to ask whether it is possible to have a tissue probability map of the brain according to aseg.mgz. If I am not wrong aseg.mgz is the MAP estimate of a Markov Random Field based segmentation hence we shall get the probability maps for each label or tissue. Is it possible? Best, Burak

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WMparc step command line
by Amy DeLuca 22 Oct '07

22 Oct '07

could someone send me the command line for the last step in recon3 stream. The new version differs from the wiki table and I need to run just that last WMParc step. Thanks Amy

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mgz header dump
by Michael Harms 21 Oct '07

21 Oct '07

I'm sure this is trivial, but I can't find the answer: How do you dump the header contents of an mgz file to the terminal? How about the optional information stored after the image data? thanks, Mike H. -- Michael Harms, Ph.D. -------------------------------------------------------------------- Conte Center for the Neuroscience of Mental Disorders Washington University School of Medicine Department of Psychiatry, Box 8134 Renard Hospital, Room 6615 Tel: 314-747-6173 660 South Euclid Ave. Fax: 314-747-2182 St. Louis, MO 63110 Email: mharms(a)wustl.edu --------------------------------------------------------------------

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Version 4.1 questions
by Kt Labadie 19 Oct '07

19 Oct '07

I have 2 questions related to version 4.1. 1) The ReconAllDevTable on the Martinos Center Freesurfer Wiki is not updated to reflect the new steps in version 4.1. Does anyone have a breakdown of these new steps? I was not sure of the flags for these new steps, or where they fit in (are they part of 2-pial, 2-cp or 3?) Is the wiki going to be updated to reflect this new version? 2) When I load an image in tkmedit (after it has been run all the way through step 3) I get an error message and it won't load the aseg. The aseg is there, I just have to load it manually. Did the following flag change with the new version? brainmask.mgz lh.white -aux T1.mgz -aux-surface rh.white - segmentation mri/aseg.mgz $FREESURFER_HOME/FreeSurferColorLUT.txt Thanks. KT LaBadie

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Talairach transformations in tkmedit and tkregister2
by Dr. Claudia Wheeler-Kingshott 17 Oct '07

17 Oct '07

Hi, We have a problem with the Talairach transformations. When we load the talairach.mgz file using tkmedit the axial and coronal orientations are swapped and displaced in the window. The puzzling thing is that if we use tkregister2, the registration is very good. Any idea of why? I found a previous message that had a similar problem but using both the tkmedit and tkregister2. Can we assume that in our case it is all fine, given that tkregister2 seems to be OK? Claudia -- ----------------------------------------- Claudia Wheeler-Kingshott, PhD Senior Lecturer Department of Inflammation Institute of Neurology, UCL Queen Square London WC1N 3BG tel. 0207 8373711 x4301 email: c.wheeler-kingshott(a)ion.ucl.ac.uk

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Interpretation of cortical thickness result
by Martin Kavec 16 Oct '07

16 Oct '07

Hi folks, I have been puzzled for a while with the results from couple of my subjects. They all have clearly visible cerebral atrophy (says neuroradiologist). I ran them through FS-4.0.1 and aseg.stat gives me, as expected, severe loss of gray matter (and others as well) as follows: GM ICV normalized Age matched reference ICV normalized What's puzzling me is the cortical thickness. Except of few locations, cortical thickness is within the STD of the controls, and at places it's even thicker. I am wondering, where such a huge GM volume loss (aseg.stats) comes from? Very simplified explanation could be that there is ^3 relation between volume and one of the dimensions of a structure ( V ~ x^3 ). In that case, it would be more sensitive to look at the volume of a parcelated cortical GM. But then, the intersubject variability of the cortical area would come into the play. Is there any other explanation? Is there a single parameter assessing cortical atrophy? Thanks a lot for the ideas in advance . Martin PS.: BTW, what is happening with the OASIS dataset analyzed using FS? When it was released the first time, there were some inconsistencies and it was pulled down from the ftp.

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Problems with make_average_subject
by jorge luis 16 Oct '07

16 Oct '07

Hello all I am trying to build an average subject under FS X86-64 v4.0.1 and I get the follow: [root@localhost ~]$ make_average_subject --subjects subj1 subj10 subj11 --out subjavr limit: descriptors: No se puede %s: %s: No se puede %s el lÃmite %s el lÃmite [root@localhost ~]$ The words in spanish should came from the operating system. Any idea? In advance thank you ____________________________________________________________________________________ Sé un Mejor Amante del Cine ¿Quieres saber cómo? ¡Deja que otras personas te ayuden! http://advision.webevents.yahoo.com/reto/entretenimiento.html

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[Fwd: optimal reconstruction.]
by Nick Schmansky 15 Oct '07

15 Oct '07

Shrikanth, I am re-posting this question to the freesurfer list, as others may have a better answer. To the best of my knowledge, there is no single error measure for which a comparison can be made of the quality of a surface reconstruction across subjects. Rather, a visual inspection of each surface, making use of tksurfer (and tkmedit), will reveal gross defects, and how faithfully it follows the wm/gm boundary. Bruce may have other suggestions. Nick -------- Forwarded Message -------- From: kulashek(a)mappi.helsinki.fi To: Nick Schmansky <nicks(a)nmr.mgh.harvard.edu> Subject: optimal reconstruction. Date: Mon, 15 Oct 2007 11:31:40 +0300 Hi, I have recently finished the construction of the inflated surfaces for 10 subjects using Freesurfer. Out of these 10 inflated surfaces how can I find the most accurate(optimal) suface, i.e. the surface with the least amount of error during the reconstruction. Thank you. Regards, Shrikanth

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hyperthreading
by Michael Harms 15 Oct '07

15 Oct '07

Hello, Question about eking out maximum machine performance: Is there a performance advantage (or alternatively penalty) for running twice as many FreeSurfer jobs (simultaneously) as physical CPUs on a Linux machine with HyperThreading enabled CPUs? That is, say you have two physical cores with HyperThreading -- the Linux OS treats this as four logical processors. However, given that Freesurfer is very 'execute' intensive is there any advantage to be gained by running 4 rather than 2 FS jobs simultaneously? Or will the total time per brain with 4 simultaneous jobs be (on average) just twice as long? thanks, Mike H. -- Michael Harms, Ph.D. -------------------------------------------------------------------- Conte Center for the Neuroscience of Mental Disorders Washington University School of Medicine Department of Psychiatry, Box 8134 Renard Hospital, Room 6615 Tel: 314-747-6173 660 South Euclid Ave. Fax: 314-747-2182 St. Louis, MO 63110 Email: mharms(a)wustl.edu --------------------------------------------------------------------

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Freesurfer October 2007