Abstract ID: 197 Monte Carlo simulations of X-ray grating interferometry based imaging systems.

Over the last couple of years the implementation of Monte Carlo (MC) methods of grating based imaging techniques is of increasing interest. Several different approaches were taken to include coherent effects into MC in order to simulate the radiation transport of the image forming procedure. These include full MC using FLUKA [1], which however are only considering monochromatic sources. Alternatively, ray-tracing based MC [2] allow fast simulations with the limitation to provide only qualitative results, i.e. this technique is not suitable for dose calculation in the imaged object. Finally, hybrid models [3] were used allowing quantitative results in reasonable computation time, however only two-dimensional implementations are available. Thus, this work aims to develop a full MC framework for X-ray grating interferometry imaging systems using polychromatic sources suitable for large-scale samples. For this purpose the EGSnrc C++ MC code system is extended to take Snell's law, the optical path length and Huygens principle into account. Thereby the EGSnrc library was modified, e.g. the complex index of refraction has to be assigned to each region depending on the material. The framework is setup to be user-friendly and robust with respect to future updates of the EGSnrc package. These implementations have to be tested using dedicated academic situations. Next steps include the validation by comparisons of measurements for different setups with the corresponding MC simulations. Furthermore, the newly developed implementation will be compared with other simulation approaches. This framework will then serve as bases for dose calculation on CT data and has further potential to investigate the image formation process in grating based imaging systems.