Optimization of grating duty cycle in non-interferometric grating-based X-ray phase contrast imaging.

Renfang Hu,Xiaobo Zhang,Gang Liu,Ronghui Luo,Chenxi Wei,Ying Xiong,Zhao Wu,Yangchao Tian,Lei Wang,Liang Guo

doi:10.1063/1.4996507

Abstract

Grating-based X-ray phase contrast imaging technology is one of the most potential imaging methods in real applications. It can be classified into two categories: interferometry and non-interferometric imaging. The non-interferometric grating-based X-ray phase contrast imaging (NIGPCI) instrument has a great advantage in the forthcoming commercial applications for the flexible system design and the use of large periodic gratings. The performance of the NIGPCI instrument depends on its angular sensitivity to a great extent. Therefore, good angular sensitivity is mandatory in order to obtain high quality phase-contrast images. Several parameters, such as the X-ray spectrum, the inter-grating distances, and the parameters of the three gratings, influence the angular sensitivity of the imaging system. However, the quantitative relationship between the angular sensitivity and grating duty cycle is unclear. Therefore, this paper is devoted to revealing their internal relation by theoretical deduction and emulation of the imaging process with the theories of linear system and Fourier optics. Furthermore, a quantitative analysis method to optimize the duty cycles of gratings is proposed and its applicability to a general NIGPCI system is verified.

Highlights

A traditional X-ray imaging technique, relying on X-ray absorption to detect the internal structure of the object, has been fully developed and widely used in many areas, such as medical diagnosis, industrial nondestructive testing, security screening, and so on
We investigate the relationship between the angular sensitivity and grating duty cycle via theoretical derivation and accomplish the optimization of grating duty cycle
The angular sensitivity of the non-interferometric grating-based X-ray phase contrast imaging (NIGPCI) system is expressed as the minimum resolvable refraction angle, which is proportional to the smallest detectable phase shift of the projection fringe of G1 grating at the plane of G2 grating, given by27,30–32 αmin

Summary

INTRODUCTION

A traditional X-ray imaging technique, relying on X-ray absorption to detect the internal structure of the object, has been fully developed and widely used in many areas, such as medical diagnosis, industrial nondestructive testing, security screening, and so on. The design energy, the parameters of the grating (period and duty cycle), and inter-grating distances are the main factors determining the angular sensitivity of the system. Optimization of these system parameters in the NIGPCI system design is very important to improve its performance. We employ the theories of linear system and Fourier optics to emulate the imaging process and discover the linear relationship of the visibility of the phase stepping curve to grating duty cycle. We investigate the relationship between the angular sensitivity and grating duty cycle via theoretical derivation and accomplish the optimization of grating duty cycle

Physical model

Numerical model

Relationship between angular sensitivity and grating duty cycle

OPTIMIZATION OF DUTY CYCLE

SUMMARY