[Mristudio-users] Number of fibers

[susumu mori]

In the current implementation of DtiStudio, tracking starts from the center
of all voxels, but it is just a procedural division. As a matter of fact,
there are programs out there, in which you can control the number of seeds
per voxel, like 10 seeds randomly distributed inside a voxel. Then you may
get 10 more fibers that penetrate your ROIs.

Does it make sense?

On Mon, Sep 12, 2011 at 3:47 PM, Rajagopalan, Venkateswaran <
rajagov2 at ccf.org> wrote:

> Thanks very much Dr.Susumu, I am not able to understand this part sorry "If
> the number of the seed points is increased, the number of the fibers
> increases too. So,
> it is parameter-dependent."
>
> Can you please throw more light on this I am not able to understand the
> following; according to my understanding DTI studio starts tracking from all
> voxels above the threshold say FA=0.2, bending angle =41 (which i set) after
> tracking from all voxels it will give me fibers running between the two ROIS
> which I choose in order to reconstruct CST or other tracts, so by seed
> points does it mean the size of these ROIs which I draw or something
> different, suppose if I keep the ROI size same in two conditions (two time
> points of scan in the same subject) then can number of fibers will make
> sense .
>
> Thanks for your time.
>
> Venkat
>
> ________________________________
>
> From: mristudio-users-bounces at mristudio.org on behalf of susumu mori
> Sent: Mon 9/12/2011 1:53 PM
> To: DTI Studio, ROI Editor, DiffeoMap Questions/Support
> Subject: Re: [Mristudio-users] Number of fibers
>
>
> Hi Vankat,
>
> This is one of the questions asked several times in the past. If you search
> the Mailing List archive (
> http://lists.mristudio.org/pipermail/mristudio-users/) with "number of
> fibers" (using ctrl-f), you can find some past communications. My typical
> reply is;
>
> The number of the fiber itself doesn't carry anatomical meaning. In
> DtiStudio, we use the exhaustive approach, meaning fiber tracking is
> initiated from the center of all pixels above the threshold. If the number
> of the seed points is increased, the number of the fibers increases too.
> So,
> it is parameter-dependent. You may be able to compare the numbers between
> subjects but it may simply reflect the size of the tracts, which can be
> also
> obtained from the number of pixels. The number of pixels is also reported
> in
> DtiStudio and has a physical dimension, which may be easier to use.
> As you can imagine, it is not possible to link "the number of fibers" to
> the real axonal fibers.
> My lab doesn't use this metric.
>
> Susumu
>
>
> On Mon, Sep 12, 2011 at 1:34 PM, Rajagopalan, Venkateswaran <
> rajagov2 at ccf.org> wrote:
>
>
>        Dear All,
>
>        After fiber tracking when I try to see statistics of FA along the
> fiber I could see in the stats file number of fibers in each slice. I am
> wondering what this number of fibers mean physiologically and how is this
> number of fibers calculated is it the number of the streamlines in a voxels.
>
>        Thanks in advance
>        Venkat
>
>
>
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