Atomic density imaging of light elements by photon-counting CT

This is a trial for decomposing a computed tomography (CT) image obtained by photon-counting CT (PCCT) into CT images of individual atomic elements constituting a material. We used the data of linear attenuation coefficients measured from 20 to 100 keV in energy bins of 4 keV in the PCCT, and additional data taken using the transmissionmeasurement method to verify the material decomposition method. Liquid samples whose materials are composed of at most three elements (H, C, and O) were selected to simplify the study. We succeeded in obtaining atomic density images for these elements without a K-edge, which transcends the two-parameter analysis, such as electron density and effective atomic number. Atomic densities provide the mass density and effective atomic number straightforwardly.