Comparison of Scatter Correction Methods for CBCT

Abstract

In contrast to the narrow fan of clinical Computed Tomography (CT) scanners, Cone Beam scanners irradiate a much larger proportion of the object, which causes several times more X-rays scattering. If this scatter is not corrected, the reconstructed images exhibit artifacts: The middle area of the object becomes darker than the outer area, as the density in the middle of the object is underestimated. We compared three methods of correcting for scatter artifacts. 1) A heuristically-estimated constant was subtracted from each projection image (Uniform Scatter Fraction). 2) A beam-hardening-type correction followed by comparing with a cylindrical norm. 3) A combination of both. 4) Using the projections, the object dimensions were estimated in order to compute the scatter with a physical model. In our preliminary results, the first method significantly reduced scatter artefacts. Method two and method three lead to similar image quality and effectively reduced scatter artifacts.