Research on dual energy grating based X-ray phase contrast imaging

Abstract

There exist some problems in a grating-based X-ray differential phase contrast imaging system, such as complex imaging system, low imaging efficiency and high requirements for step precision. The phase information extraction method of imaging system has been developed into an existing two-stepping phase shift method from the original phase stepping method, which improves the imaging efficiency and reduces the imaging radiation dose and imaging time. However, the method of two-stepping phase shift still needs to move the grating, and the requirement for accuracy of the step position is also very high. According to the problems mentioned above, in this paper we propose a dual energy multi-line X-ray source and a dual energy analysis grating. The dual energy multi-line X-ray source can emit two different levels of X-ray structure light, which can replace the X-ray source and source grating. The dual energy analysis grating is composed of two different types of scintillator materials, which are in staggered distribution. One is scintillator material that can transform high energy X-ray into visible light, and the other one can convert low energy X-ray into visible light. The dual energy analysis grating can replace traditional analysis grating and the conversion screen of X-ray CCD detector. By using the dual energy multi-line X-ray source and dual energy analysis grating in grating-based X-ray differential phase contrast imaging system, a dual energy grating-based X-ray phase contrast imaging system is proposed in this paper. In addition, in this paper we show the structure and imaging principle of the imaging system. The imaging system can achieve high and low energy X-ray imaging without moving grating. Two levels of X-ray imaging are equivalent to the analysis grating displacement π phase, which is in line with the traditional two-stepping method of two image phase shift requirements. Therefore, after the normalization processing of the two kinds of energies, the phase information can be extracted by the traditional two-stepping phase shift method. In order to validate the correctnesses of the imaging principle of the proposed imaging system and extraction method of phase information, the imaging system is simulated. The simulation is performed on the assumption that an X-ray beam passes through a polymethyl methacrylate sphere as a phase specimen, and the method is adopted by using the proposed dual energy X-ray about left and right lumbar imaging to extract phase information. The simulation result shows that the imaging system can realize normal imaging, and the first-order derivative distribution of the sphere phase extracted by the dual energy X-ray method is consistent with the experimental result.