I have to study a bit about RA, but FA should not be more than 1, although there is possibility if the fitting didn't work properly. For example, depending on the degree of anisotropy, noise, registration artifacts (motion, eddy current), it's possible to get negative diagonal elements, (physically impossible but mathematically possible) and FA becomes more than 1. In other words, by applying diffusion-weighting, signal increases. In DtiStudio, if diagonal elements become less than 0, they are replaced by 0, eliminating most of FA>1.<br>
<br><div class="gmail_quote">On Mon, Sep 13, 2010 at 4:20 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;">
<div>
<p><font size="2">Dear All,<br>
<br>
I am using recent version of DTI studio (DTISTUDIO-lates-x86.exe) to process my DTI images. I am wondering whether RA and FA maps are normalized i.e. their values range between 0-1 because in cerebral peduncle (for CST) in some of my subjects (controls) I am getting RA values above 1 and FA values close to 1 which i haven't seen while using earlier versions of DTI studio. Kindly clarify the above.<br>
<br>
Thanks in advance<br>
<br>
Venkateswaran<br>
</font>
</p>
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