南方医科大学学报

南方医科大学学报 ›› 2023, Vol. 43 ›› Issue (7): 1233-1240.doi: 10.12122/j.issn.1673-4254.2023.07.20

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锥束CT系统几何校正的偏差因素敏感性分析方法

王海龙，林国钦，段晓曼，亓孟科，武王将，马健晖，徐 圆   

  1. 南方医科大学生物医学工程学院，广东 广州 510515，南方医科大学南方医院放疗科，广东 广州 510515；萨斯喀彻温大学，萨斯喀彻温 萨斯卡通 加拿大
  • 出版日期:2023-07-20 发布日期:2023-07-20

A method for sensitivity analysis of deviation factor for geometric correction of cone-beam CT system

WANG Hailong, LIN Guoqin, DUAN Xiaoman, QI Mengke, WU Wangjiang, MA Jianhui, XU Yuan   

  1. School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, China; Department of Radiotherapy, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China; University of Saskatchewan, Saskatoon Saskatchewan, Canada
  • Online:2023-07-20 Published:2023-07-20

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摘要： 目的 提出锥束CT系统几何校正的偏差因素敏感性分析方法。方法 本研究提出中心偏差的定义及其推导，并基于Noo解析方法计算几何校正参数及利用FDK重建算法进行图像重建分析模拟钢珠点三维空间中心、投影中心以及钢珠点大小的变化对几何参数偏差及重建图像结果产生的影响。结果 当钢珠点半径在3 mm以内时，校正参数的中心偏差在[10-4]量级内，可忽略不计；钢珠点三维空间坐标单个像素的10%的高斯扰动会产生约为3个像素尺寸偏差，而钢珠点二维投影坐标的相同高斯扰动时会产生约为两个像素尺寸偏差。结论 几何校正中对钢珠点三维空间坐标产生的偏差较为敏感，对钢珠点二维投影坐标产生的偏差敏感有限，直径较小的钢珠点的偏差敏感可忽略。

关键词: 锥束CT；几何校正；图像重建；钢珠点精度偏差

Abstract: Objective To propose a sensitivity test method for geometric correction position deviation of cone-beam CT systems. Methods We proposed the definition of center deviation and its derivation. We analyzed the influence of the variation of the three-dimensional spatial center of the steel ball point, the projection center and the size of the steel ball point on the deviation of geometric parameters and the reconstructed image results by calculating the geometric correction parameters based on the Noo analytical method using the FDK reconstruction algorithm for image reconstruction. Results The radius of the steel ball point was within 3 mm. The deviation of the center of the calibration parameter was within the order of magnitude and negligible. A 10% Gaussian perturbation of a single pixel in the 3D spatial coordinates of the steel ball point produced a deviation of about 3 pixel sizes, while the same Gaussian perturbation of the 2D projection coordinates of the steel ball point produced a deviation of about 2 pixel sizes. Conclusion The geometric correction is more sensitive to the deviation generated by the three-dimensional spatial coordinates of the steel ball point with limited sensitivity to the deviation generated by the two-dimensional projection coordinates of the steel ball point. The deviation sensitivity of a small diameter steel ball point can be ignored.

Key words: cone beam CT; geometric correction; image reconstruction; steel ball point accuracy deviation