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Iterative correction of beam hardening artifacts in CT
Author(s) -
Van Gompel G.,
Van Slambrouck K.,
Defrise M.,
Batenburg K. J.,
de Mey J.,
Sijbers J.,
Nuyts J.
Publication year - 2011
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3577758
Subject(s) - attenuation , imaging phantom , iterative reconstruction , segmentation , homogeneous , beam (structure) , physics , algorithm , iterative method , optics , computer science , artificial intelligence , computer vision , thermodynamics
Purpose: 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.