【摘要】 由投影重建图像是X射线CT(computed tomography)的基础,它要求X射线沿直线传播。在X射线相位衬度CT中,不仅利用被检物体吸收X射线获得吸收衬度,而且利用被检物体改变X射线的相位分布获得相位衬度。众所周知,X射线相位分布改变必然导致X射线传播方向发生变化。于是在X射线相位衬度CT中,就在X射线直线传播必要条件和X射线改变传播方向之间产生了矛盾,这个矛盾实际上是直线和非直线之间矛盾。本文根据对立统一的观点,分析了直线和非直线之间矛盾,分别为X射线吸收信号、相移信号、折射角信号、散射角方差信号和相位二阶导数信号建立了投影直线模型。更多还原

【Abstract】 Images reconstructed from projections is the fundamental of computed tomography CT,which requires the X-ray to travel along the straight line.In X-ray phase contrast CT,the absorption contrast is obtained by specimen absorbing X-ray and the phase contrast is obtained by specimen changing the phase distribution of incidence X-ray.As well known the change of phase distribution of X-ray will inevitably lead to the change of the direction of X-ray propagation.Thus,in the X-ray phase contrast CT,there is a contradiction between the necessary conditions for the propagation of X-ray along straight lines and the change in the direction of propagation of the X-ray,which is actually a contradiction between straight and non-linear.Based on the viewpoint of unity of opposite to analyze the contradiction between the straight line and the non-straight line,projection line models for multiple contrast mechanisms,including the X-ray absorption,phase shift,refraction,ultra-small angle scattering and phase second derivative were built in this paper.更多还原