<div>Hi Lassi, </div><div><br></div>In general, inspection of the corners in an image probably does not constitute a proper assessment of bias correction algorithms. Can you describe your data a little more and perhaps I can point you to some variations you might want to try?<div>
<br></div><div>Nick<br><div><br><br><div class="gmail_quote">On Wed, Oct 7, 2009 at 8:46 AM, Lassi Paavolainen <span dir="ltr"><<a href="mailto:lassi.paavolainen@jyu.fi">lassi.paavolainen@jyu.fi</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">Hi Nick,<div class="im"><br>
<br>
On Thu, 24 Sep 2009, Nicholas Tustison wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi Lassi,<br>
<br>
You might want to take a look at the N3 algorithm implemented in ITK. It might provide what you're looking for.<br>
<br>
<a href="http://www.midasjournal.org/browse/publication/640" target="_blank">http://www.midasjournal.org/browse/publication/640</a><br>
<br>
Good luck,<br>
Nick<br>
</blockquote>
<br></div>
I have played around with that now. It looks promising but doesn't do its job completely. I have tested it with one dataset where mean intensity is around 130 in lower left corner and around 100 in upper right corner.<br>
<br>
When I run test program from your publication using shrinkFactor = 4 and using default iteration number and number of fitting levels values, I get image where difference between those areas is about 20. Running it five times difference is subtracted to around 10. I have changed the number of iterations and fitting levels without making a much of a difference in results.<br>
<br>
So it looks really promising but I would like to get the job done by running it only once. Of course results cannot be perfect (there is no perfect solution in image analysis). Do you have any idea where I should look into to make it converge to some sort of optimal result by running the filter just once?<br>
<font color="#888888">
<br>
Lassi</font><div><div></div><div class="h5"><br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
On Sep 24, 2009, at 4:23 AM, Lassi Paavolainen wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi,<br>
<br>
Does anyone know about ITK method to correct non-uniform illumination? There seems to be MRIBiasCorrection class and an example of it in InsightApplications. I'm not sure if this class can help me and anyway it doesn't seem to be very easy to use.<br>
<br>
I have read following technical report (<a href="http://www.sci.utah.edu/~tolga/pubs/UUSCI-2005-008.pdf" target="_blank">www.sci.utah.edu/~tolga/pubs/UUSCI-2005-008.pdf</a>). One of the authors seems to be Ross Whitaker who is involved in ITK too. Is there ITK implementation of that method?<br>
<br>
Lassi<br>
<br>
-- <br>
Lassi Paavolainen, M.Sc.<br>
Software Engineer<br>
BioImageXD (<a href="http://www.bioimagexd.net" target="_blank">http://www.bioimagexd.net</a>)<br>
<a href="mailto:lassi.paavolainen@jyu.fi" target="_blank">lassi.paavolainen@jyu.fi</a><br>
<br>
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</blockquote>
<br>
-- <br>
Lassi Paavolainen, M.Sc.<br>
Software Engineer<br>
BioImageXD (<a href="http://www.bioimagexd.net" target="_blank">http://www.bioimagexd.net</a>)<br>
<a href="mailto:lassi.paavolainen@jyu.fi" target="_blank">lassi.paavolainen@jyu.fi</a><br>
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