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.<div>
<br></div><div>Does it make sense?<br><br><div class="gmail_quote">On Mon, Sep 12, 2011 at 3:47 PM, Rajagopalan, Venkateswaran <span dir="ltr"><<a href="mailto:rajagov2@ccf.org">rajagov2@ccf.org</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">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,<br>
it is parameter-dependent."<br>
<br>
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 .<br>
<br>
Thanks for your time.<br>
<br>
Venkat<br>
<br>
________________________________<br>
<br>
From: <a href="mailto:mristudio-users-bounces@mristudio.org">mristudio-users-bounces@mristudio.org</a> on behalf of susumu mori<br>
Sent: Mon 9/12/2011 1:53 PM<br>
To: DTI Studio, ROI Editor, DiffeoMap Questions/Support<br>
Subject: Re: [Mristudio-users] Number of fibers<br>
<div class="im"><br>
<br>
Hi Vankat,<br>
<br>
This is one of the questions asked several times in the past. If you search the Mailing List archive (<a href="http://lists.mristudio.org/pipermail/mristudio-users/" target="_blank">http://lists.mristudio.org/pipermail/mristudio-users/</a>) with "number of fibers" (using ctrl-f), you can find some past communications. My typical reply is;<br>
<br>
The number of the fiber itself doesn't carry anatomical meaning. In<br>
DtiStudio, we use the exhaustive approach, meaning fiber tracking is<br>
initiated from the center of all pixels above the threshold. If the number<br>
of the seed points is increased, the number of the fibers increases too. So,<br>
it is parameter-dependent. You may be able to compare the numbers between<br>
subjects but it may simply reflect the size of the tracts, which can be also<br>
obtained from the number of pixels. The number of pixels is also reported in<br>
DtiStudio and has a physical dimension, which may be easier to use.<br>
As you can imagine, it is not possible to link "the number of fibers" to the real axonal fibers.<br>
My lab doesn't use this metric.<br>
<br>
Susumu<br>
<br>
<br>
On Mon, Sep 12, 2011 at 1:34 PM, Rajagopalan, Venkateswaran <<a href="mailto:rajagov2@ccf.org">rajagov2@ccf.org</a>> wrote:<br>
<br>
<br>
Dear All,<br>
<br>
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.<br>
<br>
Thanks in advance<br>
Venkat<br>
<br>
<br>
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