Fig. 1. Flowchart of three iterations of OMDRT (for example with three materials)

Fig. 2. X-ray spectrum, simulated phantom, and mass attenuation coefficient of materials used in experiments. (a) Spectrum; (b) mass attenuation coefficient of materials; (c) monochromatic image; (d) profile of column shown in Fig. 2(c)

Fig. 3. Reconstructed image and profile of multicolor projection data. (a) Reconstructed image; (b) profile

Fig. 4. Reconstructed images and mark images of base material decomposition. fn(l) is the nth material decomposition image with l iterations; On(l) is the nth material mark image with l iterations; Hn(l) is the nth non-material mark image with lth iterations; (a) 60 keV pseudo monochromatic images obtained by 1st iteration; (b) 60 keV pseudo monochromatic images obtained by 2nd iteration; (c) 60 keV pseudo monochromatic images obtained by 3rd iteration

Fig. 5. Iteratively marked image. (a) Marked image of 2nd iteration; (b) marked image of 3rd iteration

Fig. 6. Reconstructed images and mark images with morphological processing. O2(2) is mark image of bone with 2 iterations; H2(2) is mark image of non-bone with 2 iterations; f2(3) is bone image with 3 iterations; f3(3) is water image with 3 iterations; (a) combined mark image of 2nd iteration; (b) monochromatic image of 3rd iteration

Fig. 7. PSNR and NMAD of pseudo monochromatic images varying with iteration number. (a) PSNR curves; (b) NMAD curves

Fig. 8. Results of 20th iteration, with only threshold segmentation and adding morphological processing for mark images. (a)-(d) AgHg, bone, water, and pseudo monochromatic images with only threshold segmentation; (e)-(h) AgHg, bone, water, and pseudo monochromatic images with adding morphological processing for mark images

Fig. 9. Profiles of pseudo monochromatic images. (a) Profiles of pseudo monochromatic images shown in Fig. 2(c), Fig. 8(d) and Fig. 8(h); (b) partial magnification of Fig. 9(a)

Fig. 10. Reconstructed image from noisy polychromatic projection. (a) Reconstructed image; (b) profile

Fig. 11. Reconstructed images and mark images from noisy polychromatic projections. fn(l) is the nth material decomposition image with l iterations; On(l) is the nth material mark image with l iterations; Hn(l) is the nth non-material mark image with lth iterations; (a) 60 keV pseudo monochromatic images obtained by 1st iteration; (b) 60 keV pseudo monochromatic images obtained by 2nd iteration; (c) 60 keV pseudo monochromatic images obtained by 3rd iteration

Fig. 12. PSNR and NMAD of pseudo monochromatic images reconstructed from noisy polychromatic projections varying with iteration number. (a) PSNR curve; (b) NMAD curve

Fig. 13. Results of 10 iterations with proposed OMDRT for noisy polychromatic projections. (a) AgHg image; (b) bone image; (c) water image; (d) 60 keV pseudo monochromatic image

Fig. 14. Profile of pseudo monochromatic image reconstructed with 10 iterations by OMDRT