Hi Mark,<div><br></div><div>Unfortunately, this is a typical artifact we see in many EPI/DTI data. I think it's a truncation error, but not sure. If it is a truncation error, it may decrease by making the image matrix larger, but it causes loss of SNR and larger deformation. So you win some and lose some. I personally like to use a smaller matrix (use only the echoes with enough SNR) and take the artifacts as part of the game....<br>
<br><div class="gmail_quote">On Thu, Aug 4, 2011 at 3:16 PM, Mark A. Pinsk <span dir="ltr"><<a href="mailto:mpinsk@gmail.com">mpinsk@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Hi everyone,<br>
<br>
We're seeing an artifact in our DTI images (most visible in the non-DWI images, but they show up everywhere including the calculated FA maps). I assume this will negatively impact any tracking analyses. It's a checkered pattern that originates from high intensity regions (i.e. ventricles) and goes in both the frequency and the phase encode directions. Links to snapshots below. I was told by one person that they are Fourier truncation artifacts, but I was also told by another person that they are flow artifacts.<br>
<br>
Can someone clarify for me (1) what they are, (2) should I be concerned, and (3) how do I avoid them ?<br>
<br>
<a href="http://dl.dropbox.com/u/3889124/dti_snapshot1.tiff" target="_blank">http://dl.dropbox.com/u/3889124/dti_snapshot1.tiff</a><br>
<a href="http://dl.dropbox.com/u/3889124/dti_snapshot2.tiff" target="_blank">http://dl.dropbox.com/u/3889124/dti_snapshot2.tiff</a><br>
<br>
Thanks very much!<br>
Mark<br>
<br>
<br>
_______________________________________________<br>
mristudio-users mailing list<br>
<a href="mailto:mristudio-users@mristudio.org">mristudio-users@mristudio.org</a><br>
<a href="http://lists.mristudio.org/mailman/listinfo/" target="_blank">http://lists.mristudio.org/mailman/listinfo/</a><br>
Unsubscribe, send a blank email to: <a href="mailto:mristudio-users-unsubscribe@mristudio.org">mristudio-users-unsubscribe@mristudio.org</a><br>
</blockquote></div><br></div>