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

  • Kai-Xin Huang
  • Zhi Deng
  • Xiao-Fei Xu
  • Yu-Xiang XingEmail author


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 in both simulations and in practical experiments.


Spectral CT Contrast agent imaging Cramer–Rao lower bound Thresholds optimization K-edge 


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Copyright information

© China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, Chinese Nuclear Society and Springer Nature Singapore Pte Ltd. 2019

Authors and Affiliations

  • Kai-Xin Huang
    • 1
    • 2
  • Zhi Deng
    • 1
    • 2
  • Xiao-Fei Xu
    • 1
    • 2
  • Yu-Xiang Xing
    • 1
    • 2
    Email author
  1. 1.Department of Engineering PhysicsTsinghua UniversityBeijingChina
  2. 2.Key Laboratory of Particle and Radiation Imaging, Ministry of EducationTsinghua UniversityBeijingChina

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