[Mristudio-users] Number of fibers

[Rajagopalan, Venkateswaran]

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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