Tracking moving objects with megavoltage portal imaging: A feasibility study
Tracking moving objects with megavoltage portal imaging: A feasibility study
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DOI：
10.1118/1.2191009
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发表时间：
2006-05-01
期刊：
影响因子：
3.8
通讯作者：
Flentje, Michael
中科院分区：
文献类型：
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作者：
Meyer, Juergen;Richter, Anne;Flentje, Michael
四种不同的算法进行了研究，目的是确定它们是否适合跟踪对象在传统的兆伏射野图像。所考虑的算法是均方差和（MSSD），互信息（MI），相关比（CR）和相关系数（CC）。模拟研究进行了各种图像系列包含一个刚性的目标，沿沿着预定义的轨迹移动。对于每个系列的信号噪声比（SNR）是不同的，以比较噪声条件下的算法的性能。对于-6 dB的较差SNR，MSSD、CC、CR和MI的平均跟踪误差分别为2.4、6.5、39.0和17.2像素，标准差分别为1.9、12.9、19.5和7.5像素。像素的大小为0.5 mm。当在跟踪之前对图像应用均值滤波器时，这些结果分别改善为1.1、1.3、1.3和2.0像素，标准差分别为0.6、0.8、0.8和2.1像素。MSSD在现有内部软件中的实施表明，根据搜索范围，可以处理2到15张图像/s，使这种方法能够实时应用。总之，使用MSSD获得的总体几何跟踪精度最好，其次是CC、CR和MI。最简单和最好的算法，无论是在几何精度以及计算成本，是MSSD算法，因此是选择的方法。(c)2006年美国医学物理学家协会。
Four different algorithms were investigated with the aim to determine their suitability to track an object in conventional megavoltage portal images. The algorithms considered were the mean of the sum of squared differences (MSSD), mutual information (MI), the correlation ratio (CR), and the correlation coefficient (CC). Simulation studies were carried out with various image series containing a rigid object of interest that was moved along a predefined trajectory. For each of the series the signal-to-noise ratio (SNR) was varied to compare the performance of the algorithms under noisy conditions. For a poor SNR of -6 dB the mean tracking error was 2.4, 6.5, 39.0, and 17.2 pixels for MSSD, CC, CR and MI, respectively, with a standard deviation of 1.9, 12.9, 19.5, and 7.5 pixels, respectively. The size of a pixel was 0.5 mm. These results improved to 1.1, 1.3, 1.3, and 2.0 pixels, respectively, with a standard deviation of 0.6, 0.8, 0.8, and 2.1 pixels, respectively, when a mean filter was applied to the images prior to tracking. The implementation of MSSD into existing in-house software demonstrated that, depending on the search range, it was possible to process between 2 and 15 images/s, making this approach capable of real-time applications. In conclusion, the best geometric tracking accuracy overall was obtained with MSSD, followed by CC, CR, and MI. The simplest and best algorithm, both in terms of geometric accuracy as well as computational cost, was the MSSD algorithm and was therefore the method of choice. (c) 2006 American Association of Physicists in Medicine.