Studies of performance of antiscatter grids in digital radiography: effect on signal-to-noise ratio.
Studies of performance of antiscatter grids in digital radiography: effect on signal-to-noise ratio.
复制标题
DOI：
10.1118/1.596496
复制
发表时间：
1990-07
期刊：
影响因子：
3.8
通讯作者：
H. Chan;K. L. Lam;Yuzheng Wu
中科院分区：
文献类型：
--
作者：
H. Chan;K. L. Lam;Yuzheng Wu
我们建立了一个理论模型，描述了在数字X射线摄影中通过网格改善信噪比（SNR）。该模型考虑了空间变化的影响，在散射的主要比率和在大面积的对比度与结构化的背景上的量子噪声的图像，和在成像系统中的噪声的影响，如电子噪声和数字化噪声。在理论模型的基础上，分析了在采用栅格时这些因素对信噪比的影响。我们进行了实验测量，以评估在SNR的改善时，量子噪声是主要的噪声源的网格。结果发现，由于量子噪声的测量SNR改善因子与从网格的测量传输值确定的，从我们的理论模型预测的密切一致。为了评估数字射线照相系统中具有各种几何设计参数的网格的相对性能，我们采用Monte Carlo计算并确定了在各种散射条件下的一些网格的透射值。由于量子噪声，计算出的SNR改善因子与网格对SNR的测量改善很好地相关。我们的模型预测，SNR的改善因子强烈依赖于局部对比度，也对散射的主要比率。SNR改善因子在未穿透区域中比在图像的良好穿透区域中更高。
We developed a theoretical model which describes the improvement of signal-to-noise ratio (SNR) by a grid in digital radiography. The model takes into account the effects of spatial variations in the scatter-to-primary ratio and in the large-area contrast over an image with structured background on quantum noise, and the effects of noise in the imaging system such as electronic noise and digitization noise. Based on the theoretical model, we analyzed the effects of these factors on the SNR when a grid is employed. We performed experimental measurements to evaluate the improvement in the SNR by a grid when quantum noise is the dominant noise source. It was found that the measured SNR improvement factor due to quantum noise agreed closely with that determined from the measured transmission values of a grid, as predicted from our theoretical model. In order to evaluate the relative performance of grids with various geometric design parameters for digital radiographic systems, we employed Monte Carlo calculations and determined the transmission values of a number of grids under various scatter conditions. The calculated SNR improvement factor, due to quantum noise, correlated well with the measured improvement of the SNR by the grids. Our model predicts that the SNR improvement factor depends strongly on the local contrast ratio and also on the scatter-to-primary ratio. The SNR improvement factor is higher in the underpenetrated regions than in the well-penetrated regions of an image.