Figure 16.

Linear‐attenuation coefficients as functions of energy plotted in a log‐log scale, for the 20‐mg/ml iodine insert (column 1) and for the 600‐mg/ml calcium insert (column 2). The solid curves represent ground‐truth values calculated from NIST data,²⁷ along with linear‐attenuation coefficient calculated from monochromatic images at 40, 60, 80, 100, 120, 140, and 160 keV reconstructed from full‐scan data at iterations n=30 (, row 1) and 300 (, row 2). Row 3: relative errors averaged over 7 energy levels for the corresponding iodine and calcium inserts, as functions of iteration number n, along with dotted vertical lines indicating the results of iterations n=30 and 300. [Color figure can be viewed at wileyonlinelibrary.com]