Abstract
Material decomposition (MD) is an important application of computer tomography (CT). For phase contrast imaging, conventional MD methods are categorized into two types with respect to different operation sequences, i.e., “before” or “after” image reconstruction. Both categories come down to two-step methods, which have the problem of noise amplification. In this study, we incorporate both phase and absorption (PA) information into MD process, and correspondingly develop a simultaneous algebraic reconstruction technique (SART). The proposed method is referred to as phase & absorption material decomposition-SART (PAMD-SART). By iteratively solving an optimization problem, material composition and substance quantification are reconstructed directly from absorption and differential phase projections. Comparing with two-step MD, the proposed one-step method is superior in noise suppression and accurate decomposition. Numerical simulations and synchrotron radiation based experiments show that PAMD-SART outperforms the classical MD method (image-based and dual-energy CT iterative method), especially for the quantitative accuracy of material equivalent atomic number.
Highlights
Conventional polychromatic X-ray computer tomography (CT) aims at reconstructing the linear absorption coefficient, which depends on material composition and energy-related attenuation performance
In order to overcome the inevitable noise amplification of the two-step methods, we propose an optimization-based one-step decomposition method (PAMD-simultaneous algebraic reconstruction technique (SART), phase & absorption material decomposition-SART), which directly reconstructs substrate images from the differential phase and absorption projections
In the noise-free case, looking at the first and second lines of Fig 3, both methods can reconstruct the result without artifacts, but when comparing the circle structure with the lowest contrast in the third column, the boundary of the structure in image-based method is a little blurry, while the result of PAMD-SART is very sharp
Summary
Conventional polychromatic X-ray CT aims at reconstructing the linear absorption coefficient, which depends on material composition and energy-related attenuation performance. In order to overcome the inevitable noise amplification of the two-step methods, we propose an optimization-based one-step decomposition method (PAMD-SART, phase & absorption material decomposition-SART), which directly reconstructs substrate images from the differential phase and absorption projections.
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