X-ray phase contrast imaging model: application on tomography with a single 2D phase grating

Abstract

In this paper, we propose a model dedicated to X-ray phase contrast imaging, which is well adapted to the characterization or inspection of low attenuating samples. We introduce a hybrid approach that combines a ray-tracing step with a wave propagation computation. The mathematical basis of our model is described and we present a comparison of the model to experimental results, for the case of an optical fiber sample, in the framework of a free-propagation phase technique. The extension to the 3D imaging is proposed on simulated data using a grating based technique or more precisely, a multilateral shearing interferometry. This technique uses a single 2D phase grating, which has the advantage of a simpler experimental setup and can be coupled with a standard micro-focus X-ray tube and a high-resolution detector. Our phase model was implemented on the CIVA CT simulation platform and used to generate easily different sets of projection data for any type of sample. While the method for 3D reconstruction has the same basis as the classical CT, we focus mainly on the intermediate processing steps, which are required for the phase retrieval and present the results for a phantom composed of spherical objects in different materials.