Nuclear Science and Techniques

《核技术》(英文版) ISSN 1001-8042 CN 31-1559/TL     2019 Impact factor 1.556

Nuclear Science and Techniques ›› 2019, Vol. 30 ›› Issue (3): 38 doi: 10.1007/s41365-019-0563-9

• ACCELERATOR, RAY AND APPLICATIONS • Previous Articles     Next Articles

Optimized energy thresholds in a spectral computed tomography scan for contrast agent imaging

Kai-Xin Huang1,2 • Zhi Deng1,2 • Xiao-Fei Xu1,2 • Yu-Xiang Xing1,2   

  1. 1 Department of Engineering Physics, Tsinghua University, Beijing 100084, China
    2 Key Laboratory of Particle and Radiation Imaging, Ministry of Education, Tsinghua University, Beijing 100084, China
  • Received:2018-01-07 Revised:2018-05-13 Accepted:2018-06-09
  • Contact: Yu-Xiang Xing
  • Supported by:
    This work was supported by Grants from National key research and development program (No. 2016YFF0101304) and the National Natural Science Foundation of China (Nos. 61771279, 11435007).
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Kai-Xin Huang, Zhi Deng, Xiao-Fei Xu, Yu-Xiang Xing. Optimized energy thresholds in a spectral computed tomography scan for contrast agent imaging.Nuclear Science and Techniques, 2019, 30(3): 38     doi: 10.1007/s41365-019-0563-9

Abstract: Spectral computed tomography (CT) based on photon counting detectors (PCDs) is a well-researched topic in the field of X-ray imaging. When PCD is applied in a spectral CT system, the PCD energy thresholds must be carefully selected, especially for K-edge imaging, which is an important spectral CT application. This paper presents a threshold selection method that yields better-quality images in K-edge imaging. The main idea is to optimize the energy thresholds ray-by-ray according to the targeted component coefficients, followed by obtaining an overall optimal energy threshold by frequency voting. A low-dose pre-scan is used in practical implementations to estimate the line integrals of the component coefficients for the basis functions. The variance of the decomposed component coefficients is then minimized using the Cramer–Rao lower bound method with respect to the energy thresholds. The optimal energy thresholds are then used to take a full scan and gain better image reconstruction with less noise than would be given by a full scan using the non-optimal energy thresholds. Simulations and practical experiments on imaging iodine and gadolinium solutions, which are commonly used as contrast agents in medical applications, were used to validate the method. The noise was significantly reduced with the same dose relative to the non-optimal energy thresholds

Key words: Spectral CT, Contrast agent imaging, Cramer–Rao lower bound, Thresholds optimization, Kedge