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</o:shapelayout></xml><![endif]--></head><body lang=DE link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span lang=EN-US>Hello rtk users,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>I have question to the RTK FDK Filter. As far as I understand from to the fourier slice theorem the object to be reconstructed needs a circular trajectory and needs to rotate its own centre.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>Please have a look at the attached sketch. With this planar trajectory (Object, a PCB, is moved on a circle trajectpry “in-plane”, PCB itself is not rotating) do I need<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>a special filtering if I want to use FDK for planar CT with respect to the sketched trajectory ? I tried a circular in-plane trajectory where the PCB is centred and rotates<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>around its centre point. And with 100 projections I get good results. But with the trajectory I described (sketch, attached image) the results are not so good.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>Because of the row-wise ramp filter It looks like there is a directional dependency. My assumption is, and with respect to fourier slice theorem, that the missing object<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>rotation (rotation around itself) causes there directional effects.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>So my questions to the experts are. Do I need to apply a special filtering before backprojecting with FDK or is it just the wrong<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>algorithm for this kind of trajectory ?<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>kind regards,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>Robert C.<o:p></o:p></span></p></div></body></html>