Fig. 1. Different spectra and corresponding projections. (a) Spectra; (b) contour lines of projection equations with F_i=4,G_i=1; (c) projections versus F_i; (d) projections versus G_i

Fig. 2. Contour lines of projection equations with diferent weights

Fig. 3. Trajectory of iterative solutions and the curves of the relative errors with different bases. (a) Trajectory curves of 200 iteration solutions; (b) curves of the relative errors with respect to the number of iterations

Fig. 4. Simulated phantom and X-ray spectra used in experiments. (a) Dental phantom; (b) spectra

Fig. 5. Reconstructed images after 6 iterations with the E-ART method and the proposed AE-ART method

Fig. 6. Reconstructed images after 15 iterations with the E-ART method and the proposed AE-ART method

Fig. 7. Profiles of the reconstructed images in Fig.5 and Fig. 6 at the corresponding vertical line shown in Fig.4(a). (a),(b) and (c) Results from 6 iterations shown in Fig.5; (d),(e) and (f) results from 15 iterations shown in Fig.6

Fig. 8. NMAD of the reconstructed images with the E-ART method and the proposed AE-ART method. (a) Results of water images; (b) results of bone images; (c) results of monochromatic images