影响同步辐射X射线螺旋显微CT的若干因素研究

同步辐射X射线是扁平光, 传统显微CT难以对长样品实现快速、高分辨、低剂量三维成像, 螺旋扫描的引入可以很好地解决这一难题. 本文采用数字模拟和实验的方法较为系统地研究了螺距、光斑竖直高度和180° 投影数对成像质量、速度的影响. 模拟结果表明, 在螺距不大于2的前提下, 180° 投影数增大, 误差减小, CT成像速度变慢; 光斑竖直高度增大, 速度加快; 螺距增大, 速度加快, 且误差在允许范围内; 选取合适的参数值使旋转平移比为整数, 误差最小. 同时, 优化参数并在上海光源实现螺旋显微CT, 从实验上验证了模拟结果. 研究表明, 通过优化各参数, 同步辐射螺旋显微CT可以实现快速高质量三维成像, 为以后的实际应用提供了依据.

Effects of some factors on X-ray spiral micro-computed tomography at synchrotron radiation

It is difficult to obtain low-dose three-dimensional images of a long sample with high spatial resolution in a single scan using conventional X-ray micro-CT technique because the synchrotron X-ray beam is prolate. Spiral scanning is induced into synchrotron X-ray micro-CT (SR μ-CT) to resolve this problem. We investigate the effects of some factors on imaging quality and scanning speed by simulation and experiment, such as pitch, vertical beam width and projections per 180°. When the pitch is not greater than 2, it is found that the relative error and the CT scanning speed decrease while the projections per 180° increases. The scanning speed increases with vertical beam width. Furthermore, as pitch becomes greater, the scanning speed becomes faster. The relative error is minimized by choosing the appropriate parameters to make the ratio between rotation and vertical transfer be an integer. The simulated results are confirmed by the synchrotron-based spiral micro-CT (SRS μ -CT) experiments performed at the Shanghai Synchrotron Radiation Facility and parameters are optimized. The results presented herein provide a theoretical and experimental basis for future applications of SRS μ -CT.