A robust Hough transform algorithm for determining the radiation centers of circular and rectangular fields with subpixel accuracy
A robust Hough transform algorithm for determining the radiation centers of circular and rectangular fields with subpixel accuracy
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DOI：
10.1088/0031-9155/54/3/006
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发表时间：
2009-02-07
影响因子：
3.5
通讯作者：
Yang, James
中科院分区：
文献类型：
--
作者：
Du, Weiliang;Yang, James
定位辐射场中心的不确定性是导致整体位置误差的主要因素之一，因此必须最小化。在这项研究中，我们开发了一个Hough变换（HT）为基础的计算机算法定位的辐射中心的圆形或矩形领域与亚像素精度。我们发现，HT方法检测到的测试圆形字段的中心，绝对误差为0.037 +/- 0.019像素。在具有0.5 mm图像分辨率的典型电子射野成像仪上，该平均检测误差被转换为0.02 mm，这比图像分辨率精细得多。值得注意的是，这里描述的亚像素精度不包括实验不确定性，如直线加速器机械不稳定性或室内激光不准确性。与传统的质心法相比，HT法具有更高的精度，对图像噪声和伪影的鲁棒性更强。HT方法在Winston-Lutz测试中的应用被证明可以测量具有亚像素精度的球辐射中心对准。最后，将该方法应用于准直器旋转过程中辐射中心摆动的定量评估。
Uncertainty in localizing the radiation field center is among the major components that contribute to the overall positional error and thus must be minimized. In this study, we developed a Hough transform (HT)-based computer algorithm to localize the radiation center of a circular or rectangular field with subpixel accuracy. We found that the HT method detected the centers of the test circular fields with an absolute error of 0.037 +/- 0.019 pixels. On a typical electronic portal imager with 0.5 mm image resolution, this mean detection error was translated to 0.02 mm, which was much finer than the image resolution. It is worth noting that the subpixel accuracy described here does not include experimental uncertainties such as linac mechanical instability or room laser inaccuracy. The HT method was more accurate and more robust to image noise and artifacts than the traditional center-of-mass method. Application of the HT method in Winston-Lutz tests was demonstrated to measure the ball-radiation center alignment with subpixel accuracy. Finally, the method was applied to quantitative evaluation of the radiation center wobble during collimator rotation.