摘要
射线源焦点投影坐标是影响三维CT重建精度的重要几何参数,而在实际的三维CT成像系统中该参数不能直接精确测量得到。提出了一种改进的射线源焦点投影坐标精确测量方法。对单圆球目标体在锥束射线场不同位置进行多次成像,对相关联的数字化X射线摄影(DR)图像进行分组,提取每组两个圆球目标体DR投影的质心坐标,然后构造超定方程组,从而求解出射线源焦点投影坐标。实验结果表明,该方法回避了现有方法对投影椭圆度的要求,具有更高的测量精度,并且实现简单、具有较强的抗噪能力。
X-ray focus projection coordinates are the important geometrical parameters for three-dimensional （3D） CT reconstruction. But for practical 3D-CT scanning system, it is impossible to measure the position of the X-ray focus projection by direct means. An improved method to measure the X-ray focus projection coordinates with high accuracy is proposed. Through acquiring digital radiographic （DR） images of the single ball object at different positions in the cone X-ray beam, the DR images are combined to several groups which include two correlative DR images. Image processing methods are used so as to get the centroid of each projection of the ball object at different position and then to construct an over-determined equation set. By solving the over-determined equation set, the X-ray focus projection coordinates are finally obtained. The experimental results prove that the improved method is free of the severe requirements of the elliptical projection shape according to the existing method, and the accuracy of this method can satisfy the requirements of the practical scanning systems, meanwhile it is easy to realize and of high anti-noise ability.
出处
《光学学报》
EI
CAS
CSCD
北大核心
2011年第12期112-116,共5页
Acta Optica Sinica
基金
国家科技支撑项目(2011BAI02B02)
国家自然科学基金(60872080)资助课题
关键词
成像系统
锥束CT
几何标定
焦点投影坐标
超定方程
imaging systems cone beam CT geometrical calibration focus projection coordinates over-determined equation
