Direct model-based tomographic reconstruction of the complex refractive index

X-ray propagation-based phase contrast tomography (XPCT) has become popular as a method for tomographically reconstructing the complex refractive index of a material from single distance measurements. XPCT has two major advantages over traditional X-ray computed tomography (CT): It can be used at higher cone-beam magnifications, and it typically produces higher contrast. However, current XPCT reconstruction algorithms are limited to near-field diffraction, which limits both their use and the quality of reconstructions. In this paper, we present a model-based iterative reconstruction (MBIR) algorithm called complex refractive index tomographic iterative reconstruction (CRITIR). CRITIR is based on a non-linear physics based model for X-ray propagation and a prior model for the complex refractive index of the object being imaged. Unlike conventional methods, CRITIR is designed to work within and beyond the near-field diffraction region. We use simulation to show that our algorithm accurately reconstructs the object while the conventional methods result in inaccurate reconstructions with blurry edges beyond the near-field region.