Calculation of effective atomic numbers using a rational polynomial approximation method with a dual-energy X-ray imaging system

2021 ◽  
pp. 1-14
Author(s):  
Chia-Hao Chang ◽  
Yu-Ching Ni ◽  
Sheng-Pin Tseng
Keyword(s):  
Atomic Number ◽  
Polynomial Approximation ◽  
Approximation Method ◽  
Imaging System ◽  
Effective Atomic Number ◽  
Dual Energy ◽  
Calibration Model ◽  
X Ray ◽  
Rational Polynomial ◽  
X Ray Imaging

The study aims to develop a rational polynomial approximation method for improving the accuracy of the effective atomic number calculation with a dual-energy X-ray imaging system. This method is based on a multi-materials calibration model with iterative optimization, which can improve the calculation accuracy of the effective atomic number by adding a rational term without increasing the computation time. The performance of the proposed rational polynomial approximation method is demonstrated and validated by both simulated and experimental studies. The twelve reference materials are used to establish the effective atomic number calibration model, and the value of the effective atomic numbers are between 5.444 and 22. For the accuracy of the effective atomic number calculation, the relative differences between calculated and experimental values are less than 8.5%for all sample cases in this study. The average calculation accuracy of the method proposed in this study can be improved by about 40%compared with the conventional polynomial approximation method. Additionally, experimental quality assurance phantom imaging result indicates that the proposed method is compliant with the international baggage inspection standards for detecting the explosives. Moreover, the experimental imaging results reveal that the difference of color between explosives and the surrounding materials is in significant contrast for the dual-energy image with the proposed method.

A Spectrum-Adaptive Decomposition Method for Effective Atomic Number Estimation Using Dual Energy CT

2020 ◽  
Vol 2020 (14) ◽  
pp. 293-1-293-7
Author(s):  
Ankit Manerikar ◽  
Fangda Li ◽  
Avinash C. Kak
Keyword(s):  
Atomic Number ◽  
Decomposition Method ◽  
Traditional Approach ◽  
Effective Atomic Number ◽  
Dual Energy ◽  
Performance Comparison ◽  
Estimation Methods ◽  
Dual Energy Ct ◽  
Projection Data ◽  
X Ray

Dual Energy Computed Tomography (DECT) is expected to become a significant tool for voxel-based detection of hazardous materials in airport baggage screening. The traditional approach to DECT imaging involves collecting the projection data using two different X-ray spectra and then decomposing the data thus collected into line integrals of two independent characterizations of the material properties. Typically, one of these characterizations involves the effective atomic number (Zeff) of the materials. However, with the X-ray spectral energies typically used for DECT imaging, the current best-practice approaches for dualenergy decomposition yield Zeff values whose accuracy range is limited to only a subset of the periodic-table elements, more specifically to (Z < 30). Although this estimation can be improved by using a system-independent ρe — Ze (SIRZ) space, the SIRZ transformation does not efficiently model the polychromatic nature of the X-ray spectra typically used in physical CT scanners. In this paper, we present a new decomposition method, AdaSIRZ, that corrects this shortcoming by adapting the SIRZ decomposition to the entire spectrum of an X-ray source. The method reformulates the X-ray attenuation equations as direct functions of (ρe, Ze) and solves for the coefficients using bounded nonlinear least-squares optimization. Performance comparison of AdaSIRZ with other Zeff estimation methods on different sets of real DECT images shows that AdaSIRZ provides a higher output accuracy for Zeff image reconstructions for a wider range of object materials.

Experimental feasibility of dual-energy computed tomography based on the Thomson scattering X-ray source

2018 ◽  
Vol 25 (6) ◽  
pp. 1797-1802 ◽  
Author(s):  
Zhijun Chi ◽  
Yingchao Du ◽  
Lixin Yan ◽  
Dong Wang ◽  
Hongze Zhang ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Electron Density ◽  
Light Source ◽  
Atomic Number ◽  
Effective Atomic Number ◽  
Thomson Scattering ◽  
Dual Energy ◽  
Dual Energy Ct ◽  
X Ray ◽  
Dual Energy Computed Tomography

Unlike large-scale and expensive synchrotron radiation facilities, the Thomson scattering X-ray source can provide quasi-monochromatic, energy-tunable and high-brightness X-ray pulses with a small footprint and moderate cost, making it an excellent candidate for dual-energy and multi-energy imaging at laboratories and hospitals. Here, the first feasibility study on dual-energy computed tomography (CT) based on this type of light source is reported, and the effective atomic number and electron-density distribution of a standard phantom consisting of polytetrafluoroethylene, water and aluminium is derived. The experiment was carried out at the Tsinghua Thomson scattering X-ray source with peak energies of 29 keV and 68 keV. Both the reconstructed effective atomic numbers and the retrieved electron densities of the three materials were compared with their theoretical values. It was found that these values were in agreement by 0.68% and 2.60% on average for effective atomic number and electron density, respectively. These results have verified the feasibility of dual-energy CT based on the Thomson scattering X-ray source and will further expand the scope of X-ray imaging using this type of light source.

Patient‐specific pixel‐based weighting factor dual‐energy x‐ray imaging system using a priori CT data

2019 ◽  
Vol 46 (2) ◽  
pp. 528-543 ◽  
Author(s):  
Sahar Darvish‐Molla ◽  
Michael C. Reno ◽  
Mike Sattarivand
Keyword(s):  
Imaging System ◽  
A Priori ◽  
Dual Energy ◽  
Weighting Factor ◽  
Patient Specific ◽  
X Ray ◽  
X Ray Imaging ◽  
Ct Data
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