基于投影图像特征匹配的微纳CT焦点漂移校正

微纳CT射线源焦点热漂移是影响图像清晰度的重要因素之一。通过理论和仿真实验分析了射线源焦点漂移对图像清晰度的影响。利用实际微纳CT系统,实验发现焦点漂移主要是缓慢热漂移,漂移量与X射线源功率正相关,且焦点漂移具有一定随机性。据此,提出一种基于投影图像特征匹配的焦点漂移校正方法。首先,在实际CT扫描后快速采集少量参考投影,根据实际CT投影和参考投影自适应特征匹配结果求取特定角度下的焦点漂移量;其次,采用样条插值获取CT扫描过程所有的焦点漂移量;最后,根据焦点漂移量修正实际投影数据,重建得到校正后的图像。实验表明,该方法定位精度高,可大幅度减少图像畸变,图像清晰度提高近10%。

Focus drift correction for micro nano CT based on projection image feature matching

The focus thermal drift of micro nano CT ray source is one of the important factors affecting image sharpness. The influence of focus drift of the ray source on image sharpness is analyzed through theoretical and simulation experiments. With the actual micro nano CT system, experiment discovers that the focus drift is mainly slow thermal drift and the drift is positively correlated with the power of the X ray source, meanwhile the focus drift has certain randomness. On this basis, a focus drift correction method is proposed based on projection image feature matching. Firstly, a small amount of reference projection is rapidly acquired after the actual CT scanning, and the focus drift amount at specific angle is obtained according to result of adaptive feature matching between the actual projection and reference projection. Secondly, all the focus drift amounts in the CT scanning process are obtained with spline interpolation. Finally, the actual projection data are corrected according to the amount of focus drift, and through reconstruction the corrected image is obtained. Experiments show that the proposed method has high positioning accuracy, greatly reduces image distortion and improves image sharpness by nearly 10%.