Beam Hardening Artifact Correction Method for Multimaterial Computed Tomography Imaging

In a typical computed tomography (CT) system, an X-ray tube produces a polychromatic X-ray beam, resulting in beam hardening artifacts in a CT image. A correction method for the artifacts is proposed for multimaterial CT imaging with a single voltage. Unlike most correction methods, the proposed correction method can be implemented in a typical CT system without hardware changes and requires no prior information on the X-ray spectrum or material composition. In addition, image segments and preliminary calibration phantoms are not needed. The core idea is to decompose the X-ray transmission image to obtain basis projections. X-ray scattering is considered and incorporated into the optimized objective function of the decomposition model. To reduce the requirement of prior information, basis physical effects are used to express the attenuation coefficient of the materials, and the variables related to the spectrum are set as unknown. The projection of one voltage is insufficient and leads to multiple solutions of the model. To reduce the influence of multiple solutions, the projection data integral invariant is used to constrain the decomposition model. Three multimaterial samples are used to verify the correction method. Compared with the directly reconstructed images, the beam hardening artifact is obviously reduced in the images reconstructed via the proposed method. The results demonstrate the effectiveness of the proposed correction method.