16 March 2011 Material separation in x-ray CT with energy resolved photon-counting detectors
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The objective of the study was to demonstrate that more than two types of materials can be effectively separated with x-ray CT using a recently developed energy resolved photon-counting detector. We performed simulations and physical experiments using an energy resolved photon-counting detector with six energy thresholds. For comparison, dual-kVp CT with an integrating detector was also simulated. Iodine- and gadolinium-based contrast agents, as well as several soft-tissue- and bone-like materials were imaged. We plotted the attenuation coefficients for the various materials in a scatter plot for pairs of energy windows. In both simulations and physical experiments, the contrast agents were easily separable from other non-contrast-agent materials in the scatter plot between two properly chosen energy windows. This separation was due to discontinuities in the attenuation coefficient around their unique K-edges. The availability of more than two energy thresholds in a photon-counting detector allowed the separation with one or more contrast agents present. Compared with dual-kVp methods, CT with an energy resolved photon-counting detector provided a larger separation and the freedom to use different energy window pairs to specify the desired target material. We concluded that an energy resolved photon-counting detector with more than two thresholds allowed the separation of more than two types of materials, e.g., soft-tissue-like, bone-like, and one or more materials with K-edges in the energy range of interest. They provided advantages over dual-kVp CT in terms of the degree of separation and the number of materials that can be separated simultaneously.
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X. Wang, X. Wang, D. Meier, D. Meier, K. Taguchi, K. Taguchi, D. J. Wagenaar, D. J. Wagenaar, B. E. Patt, B. E. Patt, E. C. Frey, E. C. Frey, } "Material separation in x-ray CT with energy resolved photon-counting detectors", Proc. SPIE 7961, Medical Imaging 2011: Physics of Medical Imaging, 79611V (16 March 2011); doi: 10.1117/12.877469; https://doi.org/10.1117/12.877469

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