衍射增强成像的若干基础问题研究 Ⅱ.衍射增强成像的边界效应和本底影响

Studies on some basic problems about diffraction enhanced imaging Ⅱ. Edge effect and background influence

在衍射增强成像原理的基础上,通过简单的实验模型分析了衍射增强成像(DEI)的过程与特点。在摇摆曲线顶部记录的峰位图像有很好的衬度,可以直接用于观察物体的内部结构。表观吸收图像的特点与传统X射线图像相似,但折射图像具有更好的边界衬度,而且腰位折射图像的成像效果比趾位折射图像的成像效果更好。同时也发现,分析晶体的本底信号会影响DEI成像的质量,但对折射图像没有任何影响,不会引起折射图像与实际物体之间的偏差。因而,折射图像用于辨别正常组织与病变组织、工业检测等方面具有很好的可信度。

On the basis of the DEI＇s principle, a simple experimental model is used to analyze the process and character of DEI. The peak-position image, which is recorded at the peak of the rocking curve, has higher contrast than the absorption images and can show also micro-structures inside the samples. The apparent absorption image is similar to the conventional X-ray image, while the refraction image is extraordinarily sensitive to the change of the refractive index of the sample, and can clearly display edges of organic objects having different refractive indexes. The refraction image recorded in the middle position of rocking curve has better quality than that in the toe position, Furthermore, the background of the analyzer crystal affects the quality of the DEI, but does not affect the refraction image. Therefore, the refraction image has very good reliability in distinguishing normal or disease tissues, as well as for industrial inspection.