X射线CT系统投影旋转中心的测量

李保磊; 张耀军

doi:10.3788/OPE.20111905.0967

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X射线CT系统投影旋转中心的测量

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- X射线CT系统投影旋转中心的测量
- Measurement of center of rotation for projection in X-ray computed tomographic system
- 光学精密工程 2011年19卷第5期页码：967-971
- 作者机构：
  
  1. 公安部第一研究所, 北京 100048
  2. 北京大学数学科学学院, 北京 100871
- 作者简介：
- 基金信息：
  
  国家科技支撑计划资助项目(No.2009BAK64B02)()
- DOI：10.3788/OPE.20111905.0967
  中图分类号： TH703;R814.42
- 收稿日期：2010-06-25，
  
  修回日期：2010-10-27，
  
  网络出版日期：2011-05-26，
  
  纸质出版日期：2011-05-26
- 稿件说明：
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李保磊, 张耀军. X射线CT系统投影旋转中心的测量[J]. 光学精密工程, 2011,19(5): 967-971

LI Bao-lei, ZHANG Yao-jun. Measurement of center of rotation for projection in X-ray computed tomographic system[J]. Editorial Office of Optics and Precision Engineering, 2011,19(5): 967-971
李保磊, 张耀军. X射线CT系统投影旋转中心的测量[J]. 光学精密工程, 2011,19(5): 967-971 DOI： 10.3788/OPE.20111905.0967.

LI Bao-lei, ZHANG Yao-jun. Measurement of center of rotation for projection in X-ray computed tomographic system[J]. Editorial Office of Optics and Precision Engineering, 2011,19(5): 967-971 DOI： 10.3788/OPE.20111905.0967.

摘要

为了精确测量X射线CT成像系统的投影旋转中心坐标

校准投影几何坐标系

消除由其定位误差引起的CT图像伪影

在概述现有方法优缺点的基础上

分析推导了两个引理:"质点扫描一圈

其投影地址的积分为零"以及"任意两质点扫描投影正弦线的交点坐标之和为零"。依据上述引理

设定合适阈值对扫描得到的正弦图进行二值化分割

根据分割结果得到所有穿过物体射线的投影地址

计算这些投影地址的均值获得了投影旋转中心的坐标。实验结果表明

该方法能够高精度地测量投影旋转中心

有效地提高旋转中心校正后的重建图像质量

重复测量精度为0.08个像素。

Abstract

To measure the coordinate of Center of Rotation(COR) for projection in an X-ray CT imaging system

calibrate the projection geometry coordinate system

and to eliminate the CT image artifacts caused by the positioning error of COR

this paper derives two lemmas based on the advantages and disadvantages of existing methods

i.e. 'A particle is scanned a circle by a CT scanner

then the integral of the particle's projection addresses under each projection view equals to zero and 'The sum of the crossing point coordinates of projection sine curves of random two particles equals to zero. According to the above lemmas

an appropriate threshold is set to segment the sinogram to a binary image

the projection addresses of the rays penetrating the object are got based on the segmentation results and then the COR coordinate for projection is obtained by calculating the mean of these projection addresses. The experimental results show that the method can measure the COR precisely and can improve the reconstructed image quality greatly.Moreover

the repeated measurement accuracy is less than 0.08 pixel.

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Keywords

references

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