Single-energy material decomposition with grating-based x-ray phase-contrast CT

Abstract

In clinical X-ray imaging, the quantitative information in a CT scan has recently been extended by the possibility of using dual-energy information. Dual-energy CT has found its way into clinical imaging during the last few years and has been proven to add additional diagnostic information in different pathologies. It is based on a dual measurement at different photon energies, such that the energy dependence of the linear attenuation coefficient can be used for improved material discrimination. Here, we demonstrate how the dual information accessed with grating-based phase-contrast CT can be used to provide the same quantitative information. Different from dual energy, the phase-contrast measurement directly yields the electron-density and the total attenuation coefficient in a single measurement. With algebraic basis transformation this can be used for quantitative material decomposition, allowing the visualization of quantitative material maps. Further, a simple interaction parametrization has been used for the generation of effective atomic number maps and virtual monochromatic images. The approach has been demonstrated with an experimental angiography simulation with a chicken heart. The results have been compared with iodine staining, which is a current approach for ex-vivo soft-tissue contrast enhancement. The measurements have been performed at a compact laser-undulator synchrotron X-ray source with a tunable quasi-monochromatic X-ray energy. The simultaneous image acquisition guarantees an inherent registration of the two original data-sets. In total, the method provides a range of novel quantitative image representations which can be helpful for specific material discrimination tasks in medical imaging in the future.