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Hi Dianne,

dyads_dispersion was added in later versions.It shows the dispersion of orientation samples around the mean. It is an extra piece of information for the user, but it is not used in later stages of processing (i.e. probtrackx), so no need to worry about.

Cheers,
Stam

  ----- Original Message ----- 
  From: Dianne Patterson 
  To: [log in to unmask] 
  Sent: Thursday, September 22, 2011 8:10 PM
  Subject: Re: [FSL] Discrepancy between V1 and dyads1


  Dear FSL group,

  When I run bedpost (FSL 4.1.4), It does not generate dyads1_dispersion
  I've tried with 2 crossing fibers and with only 1.  I use the default bedpost options.
  My data has 25 directions and 3 B0s.

  Should I be concerned that this file is not being generated?
  Is there something else i need to do to generate it?

  Thoughts?

  Thankyou,

  Dianne


  On Thu, Sep 22, 2011 at 9:52 AM, Saad Jbabdi <[log in to unmask]> wrote:

    Don't worry!
    In Georg's case, the dyads clearly had the wrong bvecs, as they looked left-right flipped.
    In general, given that you use the right bvecs, the dyads1 and V1 will align well in deep white matter with a single strong fibre orientation, and less well where you have crossing fibres etc.


    Saad.






    On 22 Sep 2011, at 17:33, Dianne Patterson wrote:


      Should dyads1 and V1 always match?
      If so, I'm worried.
      -Dianne


      On Thu, Sep 22, 2011 at 1:56 AM, Saad Jbabdi <[log in to unmask]> wrote:

        Hi Georg,
        Are you sure you are using the same bvecs file?
        Which version of FSL/FDT are you running?

        Saad.



        On 22 Sep 2011, at 04:15, Georg Kerbler wrote:

        > Hi
        >
        > I am having some problems with bedpostx. The orientation of dyads is incorrect. I checked the orientation of V1 (with dtifit) before running bedpostx, and the orientations are correct with V1 (see attached screenshot). Any suggestions?
        >
        > Thanks

        > Georg<Screenshot-1.png>

        --
        Saad Jbabdi
        University of Oxford, FMRIB Centre

        JR Hospital, Headington, OX3 9DU, UK
        (+44)1865-222466  (fax 717)
        www.fmrib.ox.ac.uk/~saad





      -- 
      Dianne Patterson, Ph.D.
      Research Scientist
      [log in to unmask]
      University of Arizona
      Speech and Hearing Science 314
      1131 E 2nd Street, Building #71
      (Just East of Harvill)

      621-9877
      ==============
      If you write me (expecting an answer) and I don't respond within a
      day, then the UAConnect System has probably lost your message.
      You can always write me at [log in to unmask],
      because gmail actually works.




    --
    Saad Jbabdi
    University of Oxford, FMRIB Centre


    JR Hospital, Headington, OX3 9DU, UK
    (+44)1865-222466  (fax 717)
    www.fmrib.ox.ac.uk/~saad






















  -- 
  Dianne Patterson, Ph.D.
  Research Scientist
  [log in to unmask]
  University of Arizona
  Speech and Hearing Science 314
  1131 E 2nd Street, Building #71
  (Just East of Harvill)

  621-9877
  ==============
  If you write me (expecting an answer) and I don't respond within a
  day, then the UAConnect System has probably lost your message.
  You can always write me at [log in to unmask],
  because gmail actually works.