Detector Shift
The reconstructed image with artifacts
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What you can observe from this image:
- It looks smeared in one direction in general (x-direction in the
example).
- Lines which should be aligned overlap or are not connected
correctly.
- The image gets blurrier the closer you get to these
artifacts.
- Bright parts look like they got kind of a shadow.
Explanation for the artifacts
For the calculation of the fan angle γ the distance s to the central beam has to be shifted to the left by half of the maximal distance smax. To get the position on the detector from γ, the detector value t then has to be shifted back to the right by half of the detector size tmax. If either of these shifts is performed by a wrong value the mentioned artifacts occur.
A likely mistake would be to shift s and t by the same value, e.g. ½ · smax.
The correct reconstruction
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Authors
Anja Pohan, Stefan Nottrott