Quantitative assessment of a beam hole scatter correction in industrial computed tomography

Abstract

Abstract In industrial Computed Tomography (CT), scattered radiation causes a loss of quality of the reconstructed 3D volume. Scatter is caused by photon-matter interaction, whereby a photon is deflected from its initial propagation direction. The most prominent contributor to scattered radiation in the scope of photon energies occurring in industrial CT is Compton Scattering. With the used Beam Hole Array (BHA) technology for scatter correction, scatter intensities are determined by subtracting the primary intensities, which are gathered behind small apertures from the total intensities, which are gathered in the absence of the apertures. Intensities measured behind the apertures are assumed to be scatter free, since the transversal components of the radiation are strongly reduced. The scatter correction is performed by subtracting scatter intensities from primary intensities in the projection image. Improvements are evaluated for a newly developed test specimen considering image quality metrics and dimensional accuracy. The contrast could be improved especially for small structures. Cupping artifacts that express as systematic offset of grey values rising with the penetration length were reduced. Measurement deviations towards tactile references were decreased.