Type II beam hardening artifacts in phase contrast imaging

Abstract

The effects of beam hardening have previously been extended from absorption imaging to phase contrast imaging, showing a similar, albeit reduced, effect in the phase images. The effect of beam hardening on the interferometer performance, however, has not been demonstrated. In this work, the visibility reduction on a differential phase contrast imaging system due to spectral changes as a result of beam hardening is demonstrated. The implication of this reduction is an artificial increase in noise for the phase contrast image through highly-attenuating regions of the object. In addition, false signal will be recorded in the dark-field image, which normally shows only highly-scattering objects and interfaces. The results show that with added beam filtration, the effect is reduced, just as with more traditional beam hardening artifacts. However, the effect also means that one must also take into account the desired imaging task when determining the system’s design energy.