A new method to measure electron density and effective atomic number using dual-energy CT images

The purpose of this work is to present a new method to extract the electron density (${\rho }_{\text{e}}$) and the effective atomic number (Z _eff) from dual-energy CT images, based on a Karhunen-Loeve expansion (KLE) of the atomic cross section per electron. This method was used to calibrate a Siemens Definition CT using the CIRS phantom. The predicted electron density and effective atomic number using 80 kVp and 140 kVp were compared with a calibration phantom and an independent set of samples. The mean absolute deviations between the theoretical and calculated values for all the samples were 1.7 %  ±  0.1 % for ${\rho }_{\text{e}}$ and 4.1 %  ±  0.3 % for Z _eff. Finally, these results were compared with other stoichiometric method. The application of the KLE to represent the atomic cross section per electron is a promising method for calculating ${\rho }_{\text{e}}$ and Z _eff using dual-energy CT images. (paper)