Research Of Signals Biases In X-ray Diffraction Enhanced Imaging

X-ray diffraction enhanced imaging is an important method of X-ray phase contrast imaging.This imaging method acquires the internal information of an object by measuring the modulation of the object by X-rays.With this method,phase contrast imaging of human soft tissue composed of light elements such as carbon,hydrogen,and oxygen can obtain higher image contrast and measurement sensitivity than traditional absorption contrast imaging technology.It has great application prospects in medical imaging,material science,homeland security and other fields.In X-ray diffraction enhanced imaging technology,there are many factors that can affect the imaging quality,such as mechanical errors,coherence of the light source,photon statistical noise and signal bias.Among them,there have been many studies on mechanical errors,photon statistical noise and the coherence of light sources,and a large number of papers have been published,and there are few literatures that introduce signal bias in detail.This article systematically introduces the basic principles and information extraction methods of X-ray diffraction enhanced imaging,and deeply studies the influence of signal bias on imaging quality based on the three-picture method.The main work of this paper includes the following aspects:(1)Based on the photon statistical noise in X-ray diffraction enhanced imaging,the basic concepts and principles of signal bias in diffraction enhanced imaging are derived,and the theoretical formula of signal bias is derived based on the second-order expansion of Taylor series.Combining the information extraction formula of the three-picture method,the deviation of the refracted signal and the scattered signal is calculated.The results show that the refracted signal and the scattered signal are both biased estimates.Based on this,this thesis deeply studies the influencing factors of refraction and scattering signal bias.(2)The numerical simulation experiment of diffraction-enhanced imaging was carried out using the PMMA rod-scattering foil model.The numerical simulation results validate the theoretical derivation,and on this basis,the effect of the angular position of the crystal on the bias is mainly studied.The established bias model can guide the optimization of the test plan to improve the accuracy of extracting object information with the three-picture method.