Measurement of electron density and effective atomic number using dual-energy x-ray CT

The information on the electron densities of bodies is important for the treatment planning of radiotherapy. In order to obtain the electron densities directly, we have developed dual-energy X-ray computed tomography (CT) using synchrotron radiation. It was experimentally proved that the electron density was deduced with about 1% accuracy from two linear attenuation coefficient. However, the linear attenuation coefficient were measured by a few percent lower than the theoretical ones. We assumed that the less accurate linear attenuation coefficients were caused by the influence of scattered radiation and the non-linearity in the response of the detector. In comparison of the scattered radiation to the simulation results, the scattered radiation contributed at the most 0.5% to the linear attenuation coefficients. Correcting the non-linearity in the detector response functions, the values of linear attenuation coefficient were improved drastically.