I think it doesn't make too much sense to go below 0.15 for FA threshold. As FA goes down, the fiber orientation has less meaning; there is no orientation for a sphere and because of noise, even perfectly sphere media could be FA = 0.1.<div>
<br></div><div>I think Cut is a better approach. Trajectory in between two ROIs has a strong anatomical constraint and has very small false positive.</div><div><br></div><div>If you are interested in transverse diffusivity, you can use (Evalue1+Evalue2)/2. (assuming 3 Evalues are numbered 0, 1, 2).</div>
<div><br></div><div>2DFA2-3 and FA1-3 are metrics to measure difference between Evalue1 and 2 and Evalue0 and 2. We calculate them, but honestly, I'm not sure if it has much meaning.</div><div><br></div><div><br><br><div class="gmail_quote">
On Wed, Mar 6, 2013 at 12:46 PM, Prachi Dubey <span dir="ltr"><<a href="mailto:pxd2010@gmail.com" target="_blank">pxd2010@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><br>Thank you Hangyi thats very helpful. </div><div> </div><div>Do you propose it is best to stick to 0.2 threshold? or there is another lower but reliable threshold. My priorty is to get the most reproducible results for mean tract diffusion parameters. </div>
<div> </div><div>also what do you think will be more reliable for quantitative purposes, using cut function to exclude the fiber edge or using the entire tract. </div><div> </div><div>Also would like to hear your comments on eigen value1 and 2 and 2DFA2-3 and 2DFA1-3. And how these are computed, how specifically they differ from FA and Trace. </div>
<div> </div><div>Prachi<br></div><div class="gmail_quote"><div><div class="h5">On Wed, Mar 6, 2013 at 12:36 PM, Hangyi Jiang <span dir="ltr"><<a href="mailto:hjiang@jhmi.edu" target="_blank">hjiang@jhmi.edu</a>></span> wrote:<br>
</div></div><blockquote style="margin:0px 0px 0px 0.8ex;padding-left:1ex;border-left-color:rgb(204,204,204);border-left-width:1px;border-left-style:solid" class="gmail_quote"><div><div class="h5">
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<div style="font-family:Tahoma;font-size:10pt;direction:ltr"><br>
personally, I think 0.1 is too low to get reliable (or consistent) fiber tracking results.
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<br>
best,<br>
<br>
hangyi<br>
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<div style="direction:ltr"><font color="#000000" face="Tahoma"><b>From:</b> <a href="mailto:mristudio-users-bounces@mristudio.org" target="_blank">mristudio-users-bounces@mristudio.org</a> [<a href="mailto:mristudio-users-bounces@mristudio.org" target="_blank">mristudio-users-bounces@mristudio.org</a>] on behalf of Prachi Dubey [<a href="mailto:pxd2010@gmail.com" target="_blank">pxd2010@gmail.com</a>]<br>
<b>Sent:</b> Wednesday, March 06, 2013 12:10 PM<br>
<b>To:</b> DTI Studio, ROI Editor, DiffeoMap Questions/Support<br>
<b>Subject:</b> [Mristudio-users] transverse diffusion parameters<br>
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<div></div>
<div>
<div>Hi,</div>
<div> </div>
<div>Any thoughts on how low one could go on FA threshold for tracking without introducing too much noise. I am using FA=0.2, and a lot of my patients have very severely atropic tracts and it is excluding a lot of the data. I can track more fibers if go as
low as 0.1 but that makes me worry if I am introducing tracking error.</div>
<div> </div>
<div>Also what has your experience been with transverse diffusion values, eigen value1 and 2 and 2DFA2-3 and 2DFA1-3. In my dataset they are more sensitive than FA or Trace.
</div>
<div> </div>
<div>Any thoughts, comments appreciated. Prachi<span><font color="#888888"><br clear="all">
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-- <br>
</font></span></div><span><font color="#888888">
<div> </div>
<div>Prachi Dubey, MD MPH</div>
<div>ph:<a href="tel:4109614841" value="+14109614841" target="_blank">4109614841</a></div>
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<br></blockquote></div><div class="HOEnZb"><div class="h5"><br><br clear="all"><br>-- <br><div> </div>
<div>Prachi Dubey, MD MPH</div>
<div>ph:<a href="tel:4109614841" value="+14109614841" target="_blank">4109614841</a></div>
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