We study flat detectors for X-ray imaging performance degradation. In cone beam C-arm-CT, memory effects have a
detrimental effect on image quality. Depending on the magnitude and history of irradiance differences, detector
sensitivity variations may persist for a long period of time (days) and are visible as rings upon 3D reconstruction. A new
method is proposed for reducing memory effects produced in CsI:Tl based Flat Detector X-ray imaging, which is based
upon trap-filling by UV-light. For experiments, a commercial detector has been modified such that UV back-lighting is
accomplished. A regular LED refresh light array for reducing photodiode temporal effects is interleaved with UV LED
sub-arrays of different wavelengths in the near UV range. The array irradiates the scintillator through translucent parts of
the detector substrate. In order to assess the efficacy of the method, ghost images are imprinted by well-defined
transitions between direct radiation and attenuated or shuttered radiation. As an advantage, the new method accomplishes
ghost-prevention, either by (1) continuous trap-filling at image-synchronous UV light pulsing, or (2) by applying a single
dose of UV light. As a result, ring artefacts in reconstructed
3D-images are reduced to low levels. An effective
wavelength has been found and an equilibrium UV dosage could be set for effective trap-filling. The overall sensitivity
of the detector increases at saturated trap-filling. It was found that with optimised detector settings, i.e. optimum
saturated trap-filling, the dependence on X-ray irradiation levels is low, so that the usage of the detector and its
performance is robust.
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