Dear Robert,
Your description of the trajectory is very obscure to me. Maybe you have
a very unusual X-ray system. Could you make the following points clear :
- what is a PCB ?
- what is fixed/moving in your system (we need this information for the
object, the source and the detector), and what kind of trajectories have
the moving parts ?
- can you re-draw your sketch with just 2 or 3 positions (ideally, on
similar but separate drawings), each one with the object, the source and
the detector ?
If you do that, we should have a clear understanding of how your
acquisition goes, and be able to give you appropriate advice.
Best regards,
Cyril
On 10/10/2017 15:02, Robert Calliess wrote:
Hello rtk users,
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.
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
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
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.
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
rotation (rotation around itself) causes there directional effects.
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
algorithm for this kind of trajectory ?
kind regards,
Robert C.
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