Scattering correction using continuously thickness-adapted kernels

Quantitative reconstruction values are often miscalculated in Cone Beam Computed Tomography (CBCT) due to the presence of secondary radiation originating from scattering of photons inside the object and detector under consideration. The effect becomes more prominent and challenging in case of X-ray source of high energy (over a few 100 keV) which is used in industrial Non-Destructive Testing (NDT), due to higher scatter to primary ratio (SPR). This paper describes a scatter correction algorithm for correcting the combined scattering due to the object and the detector based on variations in Scatter Kernel Superposition (SKS) method. Scatter correction is performed for homogeneous and heterogeneous objects in a robust iterative manner suitable for high SPR, using pencil beam kernels which are simulated in computed tomography (CT) module of the CIVA software for NDT simulations. Two methods for scatter correction using SKS approach are discussed and compared in the paper. In the first method, we use a discrete approach in which kernels for only few thicknesses are used. In the second method a continuous approach is proposed where the kernels are analytically parameterised for all thicknesses. The results obtained after scatter correction are well within the expected reconstruction values. The continuous method produces better edge enhanced corrected projections and the method results in improved reconstruction values than the discrete method.