Multi-material linearization beam hardening correction for computed tomography.

Since beam hardening causes cupping and streaking artifacts in computed tomographic images, the presence of such artifacts can impair both qualitative and quantitative analysis of the reconstructed data. When the scanned object is composed of a single material, it is possible to correct beam hardening artifacts using the linearization method. However, for multi-material objects, an iterative segmentation-based correction algorithm is needed, which is not only computationally expensive, but may also fail if the initial segmentation result is poor. In this study, a new multi-material linearization beam hardening correction method was proposed and evaluated. The new method is fast and implemented in the same manner as a mono-material linearization. The correction takes approximately 0.02 seconds per projection. Although facing a potential disadvantage of requiring attenuation measurements of one of the object's constituent materials, applying the new method has demonstrated its capability for a multi-material workpiece with substantial reduction in both cupping and streaking artifacts. For example, the study showed that the absolute cupping artefacts in steel, titanium and aluminum spheres were reduced from 22%, 20% and 20% to 5%, 1% and 0%, respectively.