[Rtk-users] FDK for planar ct

[Robert Calliess]

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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