Fig. 1. Diagrams of experimental models. (a) Slice of the silicon used in the simulation; (b) model of silicon cylinder

Fig. 2. Cures of linear attenuation coefficient

Fig. 3. Subtraction fusion results of spectra. (a) Subtraction fusion result of two spectra; (b) subtraction fusion result of three spectra;(c) subtraction fusion result of four spectra

Fig. 4. Simulation results of reconstruction images before and after subtraction fusion projection. (a) Image reconstructed with 60 kV polychromatic projection; (b) image reconstructed with 70 kV polychromatic projection; (c) image reconstructed with 90 kV polychromatic projection; (d) image reconstructed with the proposed subtraction fusion projection

Fig. 5. Curves of gray value of CT reconstruction images at the straight line in Fig. 4

Fig. 6. Single material experiment results of reconstruction images before and after subtraction fusion projection. (a) Image reconstructed with 60 kV polychromatic projection; (b) image reconstructed with 70 kV polychromatic projection; (c) image reconstructed with 90 kV polychromatic projection; (d) image reconstructed with the proposed subtraction fusion projection

Fig. 7. Curves of gray value of reconstruction images at the straight line in Fig. 6

Fig. 8. Multi-material experiment results of reconstruction images before and after subtraction fusion projection. (a) Image reconstructed with 60 kV polychromatic projection; (b) image reconstructed with 70 kV polychromatic projection; (c) image reconstructed with 90 kV polychromatic projection; (d) image reconstructed with the proposed subtraction fusion projection

Fig. 9. Curves of gray value of CT reconstruction images at the straight line in Fig. 8

Table 1. Scanning parameters of voltage, current, and exposure time