Fig. 8.

Results of energy spectrum estimation using the anthropomorphic thorax phantom. (a) and (b) are the 100 and 140-kV CT images, respectively. Display window for the images: ($-150$ and 150 HU). (c) and (d) are the segmentation-based and the proposed DECT-based spectra estimations using the raw projection data acquired with standard attenuation coefficients, respectively. (e) and (f) are the segmentation-based and the DECT-based spectra estimations, respectively, using the raw projection data acquired with 98% attenuation coefficients.