锥束CT圆轨道扫描的几何校正

周凌宏; 李翰威; 徐圆; 骆毅斌; 齐宏亮

doi:doi:10.3788/ope.20142210.2847

光学精密工程, 2014, 22 (10): 2847, 网络出版: 2014-11-06

锥束CT圆轨道扫描的几何校正

Geometry calibration for circular trajectory scanning in cone-beam CT

论文大纲

周凌宏 ^*李翰威徐圆骆毅斌齐宏亮

作者单位

南方医科大学生物医学工程学院,广东广州 510515

锥束CT 几何校正图像重建圆轨道圆环点 cone-beam CT geometry calibration image reconstruction circular trajectory circular point

摘要

借鉴针孔摄像机模型,提出了一种锥束CT圆轨道扫描的几何校正方法,用于有效降低由系统几何误差所带来的重建图像伪影。首先,利用共轴旋转的钢球在探测器上所成椭圆像的特征求取圆环点;然后,结合极线约束条件建立绝对二次曲线像的约束方程,通过线性求解获得系统的内参数;最后,在求得内参数的基础上,通过几何方法和椭圆参数建立系统的外参数方程,求解系统的外参数。实验结果显示：利用本文方法进行锥束CT几何校正的内参数标定精度和外参数标定精度分别为0.193%和0.2%。本文方法能够精确地求解出所有失真参数,建立完整的几何模型,消除重建时因几何误差所带来的几何伪影,而且校正体模制作简单,应用性较强,适用于所有圆轨道CT。

Abstract

Based on the pinhole camera model,a geometry calibration method for circular trajectory scanning in cone-beam CT was proposed to reduce the geometric artifact of a reconstructed image caused by system errors. Firstly, the properties of the projected ellipses on the detector generated by the coaxial rotating steel balls were used to deduce circular points. Then,the constraint equations of absolute conic were established based on the polar constraint condition and the intrinsic parameters were obtained by linearly calculation. Finally, the extrinsic parameters can be figured out with the geometry method and ellipse parameters based on the intrinsic parameters. Experimental results indicate that the relative precision of intrinsic parameters and the extrinsic parameters are respectively 0.193% and 0.2% while using this method to calibrate the cone-beam CT system. It concludes that the proposed calibration process is able to solve all distortion parameters, build geometric model and eliminate the artifacts caused by the misaligned geometry on the reconstruction images.The method is characterized by simpler modelling, stronger application ability, and could be used in all circular orbit CTs.

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周凌宏, 李翰威, 徐圆, 骆毅斌, 齐宏亮. 锥束CT圆轨道扫描的几何校正[J]. 光学精密工程, 2014, 22(10): 2847. ZHOU Ling-hong, LI Han-wei, XU Yuan, LUO Yi-bin, QI Hong-liang. Geometry calibration for circular trajectory scanning in cone-beam CT[J]. Optics and Precision Engineering, 2014, 22(10): 2847.

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