title: Iterative correction of beam hardening artifacts in CT.
abstract: OBJECTIVE
  To reduce beam hardening artifacts in CT in case of an unknown x-ray spectrum and unknown material properties.
  
  
  METHODS
  The authors assume that the object can be segmented into a few materials with different attenuation coefficients, and parameterize the spectrum using a small number of energy bins. The corresponding unknown spectrum parameters and material attenuation values are estimated by minimizing the difference between the measured sinogram data and a simulated polychromatic sinogram. Three iterative algorithms are derived from this approach: two reconstruction algorithms IGR and IFR, and one sinogram precorrection method ISP.
  
  
  RESULTS
  The methods are applied on real x-ray data of a high and a low-contrast phantom. All three methods successfully reduce the cupping artifacts caused by the beam polychromaticity in such a way that the reconstruction of each homogeneous region is to good accuracy homogeneous, even in case the segmentation of the preliminary reconstruction image is poor. In addition, the results show that the three methods tolerate relatively large variations in uniformity within the segments.
  
  
  CONCLUSIONS
  We show that even without prior knowledge about materials or spectrum, effective beam hardening correction can be obtained.
authors: IBBT-Vision Lab, Universiteit Antwerpen, 2610 Antwerp, Belgium.
authors: G
authors: G
authors: Van Gompel
authors: K
authors: K
authors: Van Slambrouck
authors: M
authors: M
authors: Defrise
authors: K J
authors: KJ
authors: Batenburg
authors: J
authors: J
authors: de Mey
authors: J
authors: J
authors: Sijbers
authors: J
authors: J
authors: Nuyts
mesh_terms: D016477:Artifacts; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D019047:Phantoms, Imaging; D019904:Polymethyl Methacrylate; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D019904:Polymethyl Methacrylate