TY - JOUR
AU - Luo, Shuqian
AB - BACKGROUND: The beam hardening artifact is one of most important modalitiesof metal artifact for polychromatic X-ray computed tomography (CT), which can impair theimage quality seriously.OBJECTIVE: An iterative approach is proposed to reduce beam hardeningartifact caused by metallic components in polychromatic X-ray CT.METHODS: According to Lambert-Beer law, the (detected) projections can beexpressed as monotonic nonlinear functions of element geometry projections, which are thetheoretical projections produced only by the pixel intensities (image grayscale) ofcertain element (component). With help of a prior knowledge on spectrum distribution ofX-ray beam source and energy-dependent attenuation coefficients, the functions haveexplicit expressions. Newton-Raphson algorithm is employed to solve the functions. Thesolutions are named as the synthetical geometry projections, which are the nearly linearweighted sum of element geometry projections with respect to mean of each attenuationcoefficient. In this process, the attenuation coefficients are modified to makeNewton-Raphson iterative functions satisfy the convergence conditions of fixed pointediteration(FPI) so that the solutions will approach the true synthetical geometryprojections stably. The underlying images are obtained using the projections by generalreconstruction algorithms such as the filtered back projection (FBP). The image grayvalues are adjusted according to the attenuation coefficient means to obtain proper CTnumbers.RESULTS: Several examples demonstrate the proposed approach is efficient inreducing beam hardening artifacts and has satisfactory performance in the term of somegeneral criteria. In a simulation example, the normalized root mean square difference(NRMSD) can be reduced 17.52% compared to a newest algorithm.CONCLUSIONS: Since the element geometry projections are free from the effectof beam hardening, the nearly linear weighted sum of them, the synthetical geometryprojections, are almost free from the effect of beam hardening. By working out thesynthetical geometry projections, the proposed approach becomes quite efficient inreducing beam hardening artifacts.
TI - Reduce beam hardening artifacts of polychromatic X-ray computed tomography by          an iterative approximation approach
JF - Journal of X-Ray Science and Technology
DO - 10.3233/xst-16187
DA - 2017-06-13
UR - https://www.deepdyve.com/lp/ios-press/reduce-beam-hardening-artifacts-of-polychromatic-x-ray-computed-0D2WfYASj3
SP - 417
EP - 428
VL - 25
IS - 3
DP - DeepDyve
ER -