Reconstruction algorithm for polychromatic CT imaging: Application to beamhardening correction

This paper presents a new reconstruction algorithm for both single- and dua l-energy computed tomography (CT) imaging. By incorporating the polychromat ic characteristics of the X-ray beam into the reconstruction process, the a lgorithm is capable of eliminating beam hardening artifacts. The single ene rgy version of the algorithm assumes that each voxel in the scan field can be expressed as a mixture of two known substances, for example, a mixture o f trabecular bone and marrow, or a mixture of fat and flesh. These assumpti ons are easily satisfied in a quantitative computed tomography (QCT) settin g, We have compared our algorithm to three commonly used single-energy corr ection techniques. Experimental results show that our algorithm is much mor e robust and accurate. We have also shown that QCT measurements obtained us ing our algorithm are five times more accurate than that from current QCT s ystems (using calibration). The dual-energy mode does not require any prior knowledge of the object in the scan field, and can be used to estimate the attenuation coefficient function of unknown materials. We have tested the dual-energy setup to obtain an accurate estimate for the attenuation coeffi cient function of K2HPO4 solution.