利用图像相关法精确测量3D-CT成像系统焦距

对于实际的3D-CT成像系统,射线源焦点和物体旋转轴中心的位置不能直接测量,如何采取简单易行的方法精确测量二者之间的距离(即系统焦距)成为一项工程技术难点.通过双圆目标体二次成像获得射线数字成像(DR,Digital Radiography)图像,对各DR图像进行自相关处理,获得双圆投影中心距,再通过解析方法求解出系统焦距值.实验结果表明,测量精度达到了实际扫描系统的重建要求.该方法实现简单, 具有较强的抗噪能力,可实现自动测量.

Method for measuring the focal distance of 3D-CT imaging system with high accuracy using image auto-correlation

In the three dimensional computed tomography imaging system,it is impossible to measure the X-ray focus to object-rotating-axis distance(FOD) by direct means,so how to obtain the value of FOD with simple and feasible method is an involved engineering problem.Through acquiring the digital radiography(DR) images of the double-circled object at two imaging positions,the auto-correlation operation was executed,so as to get distance of the two circles' projection center.Then through solving equations,the value of FOD was finally obtained.Experiment results prove that the accuracy of this method can satisfy the requirements of the practical scanning system.This testing method is also easy to realize and of high anti-noise ability.Furthermore,it can be realized automatically by software.