<br>Hi Alice,<br><br> Welcome to ITK !<br><br>Thanks for the detailed description of the problem.<br><br><br>The outcome of the Demosn registration algorithm<br>is and image that has the same grid as the Fixed <br>
image, but is populated with the intensity levels<br>of the Moving image.<br><br>If in your case:<br><br>Fixed Image = Cylinder at value 5000<br>Moving Image = Ellipse at value 4860<br><br>Then the outcome of the registration process<br>
should be an at value 4860.<br><br>Is that what you observe ?<br><br>Also, please notice that the Demons registration<br>is based on the assumption that both images have<br>the same intensity distribution. That is, in principle,<br>
you should rescale the intensities of both images <br>before you pass them as input to the Demons filter.<br><br>You may also need to blur the images a bit in order<br>to create ramps of intensity in the border of the objects,<br>
to make possible for Demons to compute displacement<br>vectors based on the direction of the gradient.<br><br>(maybe a screenshot of your images will helpful).<br><br><br><br> Regards,<br><br><br> Luis<br>
<br><br>-----------------------------------------------------------------<br><div class="gmail_quote">On Fri, Apr 23, 2010 at 10:33 AM, calice14 <span dir="ltr"><<a href="mailto:gtg102x@mail.gatech.edu">gtg102x@mail.gatech.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;"><br>
Hello all,<br>
<br>
I have a quick question about Demon's Registration. I have successfully<br>
implemented an example, but the results were not what I expected. The<br>
simulated phantom are of ellipsoid and cylinder shape. One constrain for the<br>
two phantoms is, the total intensities of the two phantoms are the same. So<br>
for the cylinder phantom, the pixel value is 5000 while for ellipsoid it's<br>
4860. After registration, I got the result phantom which shape can match the<br>
cylinder. The problem is, the pixel intensity of the registered images<br>
followed the moving phantom(ellipsoid 4860), not the fixed phantom (cylinder<br>
5000).<br>
As it's assumed that Demon registration should keep the total intensity in<br>
the registered images, I'm wondering why my registered images don't have the<br>
correct pixel value (4860)?<br>
<br>
Is the Demon's Algorithm not implemented to keep total intensity values<br>
constant after registration?<br>
<br>
Please excuse me if this seems trivial. I am a very much a newbie to the<br>
image registration world :)<br>
<br>
Thanks all,<br>
<br>
Alice Cheung<br>
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