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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Hi all,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>I’m doing a 2D 3D registration between fluoroscopic
images and CT images, creating a DRR. Since I have several local optima I use a
multi resolution approach. I scale the images by a factor of two and do
Gaussian blurring. So I scale in 4 steps. First I register the images with one eighth
of the original size, than with one fourth, with the half size and finally with
the original size. But I have local optima in the first step. So it leads me to
misregistration when my starting point is too far away from the final point
when my images are correct registered. I can avoid this problem with using a
different step size for the Powell optimizer. But when I find a good step size
for one starting point it often is useless for other starting points. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>My images are cardiac images, where the aorta and the
spine can be seen very clearly. I use the Gradient Difference Metric ( not exactly
the ITK-Implementation, I changed it a bit, and it worked very well in several tests
). <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>Do you have an idea how I could find good starting
points or how to choose the step size for the Optimizer, depending on the
information the image gives me? Or should I use another Optimizer? What is your
experience? I’m looking forward to your answers.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>Regards<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>Sven<o:p></o:p></span></font></p>
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