Single absorption grating based X-ray phase contrast CT using Timepix detector

Abstract

Single absorption grating based X-ray phase contrast imaging (XPCI) with a hybrid pixel detector Timepix is a promising technique in many application fields (material sciences, biology, medicine etc.). Conventional coded aperture approach with microfocus source uses two absorption gratings where one of them is moved in steps (so-called phase stepping). In contrast to that, the proposed XPCI approach provides the absorption, phase contrast and dark field images from a single acquisition. This leads to higher mechanical stability of the system and decrease of the delivered dose. Moreover, faster data acquisition increases the usability of the system for CT measurements and dynamic phase radiography. Custom-built laboratory X-ray imaging setup equipped with Timepix detector and nano-focus X-ray tube was utilized for the measurements. The maximal source to detector distance (SDD) available in the setup is roughly 90 cm. Such system can provide long enough phase propagation distance while using the absorption grating with 60 μm strip period, 55 μm large detector pixels and three pixel illumination. The system enables insertion and positioning of both 1D and 2D absorption gratings producing micro-line or micro-pencil beams, respectively. The positioning stages of the used system allow to acquire a series of phase contrast images taken under different angles and thus to carry out phase contrast computed tomography (CT). CT reconstructions were performed by both in-house and commercial software packages. Results of pilot CT measurements of phantoms objects are presented in the contribution.