McParland B J
Department of Clinical Physics, Ontario Cancer Institute/Princess Margaret Hospital, Toronto, Canada.
Med Phys. 1993 May-Jun;20(3):679-85. doi: 10.1118/1.597143.
An uncertainty analysis of a field placement error measurement method using correlations between digital portal and simulation images has been performed. This analysis used the Monte Carlo method to simulate random uncertainties arising in image registration and portal field edge detection. The uncertainty analysis used data from a field placement error study to predict the dependences of the measurement method upon image matchpoint number and spatial distribution, image registration, and uncertainties arising in the detection and description of the field edge in a portal image. It was shown that the uncertainty in the field registration had the most significant effect upon the measurement uncertainty, whereas the number of matchpoints had an extremely limited effect (beyond the minimum required for the mathematical procedure used in registration). In contrast, it was shown that an accurate field placement error measurement required that the number of pixels describing a field edge used for comparisons should exceed 20, thus automatically setting a minimum field length necessary for field placement comparisons. It was also shown that the spatial uniformity of the matchpoints in an image pair had a limited effect upon the field placement error measurement, provided that the points are distributed over about 15% of the image area.
已对一种利用数字射野与模拟图像之间的相关性来测量射野摆位误差的方法进行了不确定性分析。该分析采用蒙特卡罗方法来模拟图像配准和射野边缘检测中产生的随机不确定性。不确定性分析利用了射野摆位误差研究中的数据，以预测测量方法对图像匹配点数量和空间分布、图像配准以及射野图像中射野边缘检测和描述所产生的不确定性的依赖性。结果表明，射野配准中的不确定性对测量不确定性影响最为显著，而匹配点数量的影响极为有限（超出配准所用数学程序所需的最小值）。相比之下，结果表明，准确的射野摆位误差测量要求用于比较的描述射野边缘的像素数量应超过20，从而自动设定射野摆位比较所需的最小射野长度。还表明，图像对中匹配点的空间均匀性对射野摆位误差测量的影响有限，前提是这些点分布在图像面积的约15%上。
