Reduction of Beam-Hardening Artifacts in X-Ray CT

Our goal is to decrease the importance of beam-hardening artifacts in X-ray computed tomography by addressing the polyenergetic nature of the X-ray source. We use the same physical model as De Man and al (1998). We next adopt an estimation framework for the reconstruction: the attenuation coefficients are determined by a likelihood-based estimator. This approach leads to minimization of an objective function which exhibits a complex structure. Nonetheless, we develop a numerical procedure with satisfactory numerical efficiency: we use a nonlinear conjugate gradient method. The three major contributions of this communication are: the positivity of the solution ensured by a change of variables, the convergence properties of the algorithm, and a satisfying computation time