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根据Zernike相衬观察法的基本思想和Fresnel-Kirchhoff衍射理论,采用傅里叶变换和卷积处理,考虑到临床实际,利用振幅近似和相位缓变条件,将X射线经过生物组织产生的相位改变转换成强度分布.在所导出的理论公式的基础上,作出相位衬度和吸收衬度与物平面到像平面距离的关系曲线.分析得到X射线相位衬度成像的最佳物像距离,并通过微聚焦X射线成像装置对蟑螂成像的实验加以验证,其结果表明理论所预言的成像最佳位置符合度较高.
According to the basic idea of Zernike phase contrast observation and the Fresnel-Kirchhoff diffraction theory, Fourier transform and convolution are used to take into account the clinical practice, the use of amplitude approximation and phase change conditions, the X-ray phase generated by the biological tissue changes And then converted into the intensity distribution.On the basis of the derived theoretical formula, the relationship between phase contrast and absorption contrast and the distance from the object plane to the image plane is obtained.The optimal object distance for the contrast imaging of X-ray phase is obtained Experiments on cockroach imaging with a microfocused X-ray imaging device were performed and the results showed that the theoretical best-fit imaging position was well-matched.