Andrew,<br><br>This seems a question you'd better ask to Siemens, but I have several general comments;<br>1) If your Siemens scanners are well calibrated, you should not see that much eddy current, which manifests as a bright high-FA ring especially at the front and back of the brain. If you don't see it, eddy current-corrected or not, you don't have to worry about it.<br>
2) You want to do affine registration to correct both eddy current-distortion and motion-caused misregistration. No matter what algorithms you use, the solution is only approximation and you get different solutions depending on which algorithm you use (or even by using different parameters using the same algorithm). Therefore, you won't get a clear answer by comparing your Siemens results with other software such as DtiStudio.<br>
3) Probably the best way to tell if the Siemens console does affine registration is;<br>> the first and the last slice often become partial because of X or Y rotation.<br>> Compare to images without registration (you can create this by processing DICOM using DtiStudio without AIR registration), registered images seem blur and higher SNR because of pixel interpolation necessary for registration.<br>
<br>I hope this helps.<br><br><div class="gmail_quote">On Tue, Sep 29, 2009 at 1:01 PM, Andrew Bender <span dir="ltr"><<a href="mailto:bender@wayne.edu">bender@wayne.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Hello all,<br>
<br>
This is less of a DTIstudio question than a practical consideration<br>
for DTI processing. Specifically, our institution has a newly<br>
installed Siemens 3T Magnetom Verio scanner and the console has the<br>
option of outputting computed DTI maps for FA, ADC, radial and axial<br>
diffusivities, and eigenvalues. However, nobody I've asked is clear<br>
as to whether these have been corrected for eddy current distortion<br>
when the console generates them. Does anybody know whether these<br>
console-generated DTI maps have been corrected or otherwise AIR<br>
registered? I've read recently that some newer consoles incorporate<br>
such correction algorithms, but our MR techs do not know and emails to<br>
Siemens have not been returned.<br>
<br>
Obviously, corrected DTI maps that don't require the same degree of<br>
pre-processing are preferable for workflow considerations. I'm<br>
planning on doing some comparisons for purposes of further validation<br>
using the AIRtool affine registration on the raw dicom images before<br>
generating the DTI maps in DTIstudion and Analyze, and comparing ROIs<br>
between those and the Siemens console generated maps to see if there<br>
are differences in output quality.<br>
<br>
Thanks in advance for your help.<br>
<br>
-Andrew<br>
<br>
<br>
************************************************<br>
Andrew R. Bender, M.A.<br>
Graduate Research Assistant<br>
Cognitive Neuroscience of Aging Lab<br>
Department of Psychology<br>
Institute of Gerontology<br>
Wayne State University<br>
87 E. Ferry Street<br>
Detroit, Michigan 48202<br>
<a href="mailto:bender@wayne.edu">bender@wayne.edu</a><br>
(313) 871-0710<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>