In optimizing the imaging conditions, changes in image quality due to scattered radiation are important evaluation targets. This study focuses on the evaluation of the image quality improvement characteristics obtained using anti-scatter grids in digital x-ray imaging, and proposes a frequency-dependent modulation transfer function (MTF) improvement factor, as a new evaluation index. Accordingly, the purpose of this study is to clarify the validity and the usefulness of this proposed index in the performance evaluation of grids. The proposed method is applied to evaluate several types of grids with different grid densities and ratios, and the characteristics of grids exhibiting different performances are examined. The proposed index is calculated based on the MTF measurement by using an edge test device. The results show that changed according to grid type and scatter conditions. In particular, a remarkable difference was observed in the high scatter condition compared with the low condition. in the vertical direction with regards to the absorbing strips shows a peak at 0.2–0.5 cycles/mm and be a constant value from approximately 1 cycle/mm; while in the parallel direction is a constant value with respect to changes in spatial frequency. It is shown that could be used to accurately describe the characteristics of a grid under different imaging conditions. We believe that the use of the proposed index could expand the options for optimizing imaging conditions when using grids.

在优化成像条件时，散射辐射引起的图像质量变化是重要的评价目标。本研究侧重于对数字X射线成像中使用抗散射网格获得的图像质量改进特性进行评估，并提出了频率相关调制传递函数（MTF）改进因子，作为新的评估指标。因此，本研究的目的是阐明该指标在网格性能评估中的有效性和实用性。拟议的方法被应用于评估具有不同网格密度和比率的几种类型的网格，并检查表现出不同性能的网格的特性。建议指标是通过使用边缘测试设备基于 MTF 测量计算得出的。结果表明，根据网格类型和散射条件而变化。特别是，与低散射条件相比，在高散射条件下观察到了显着差异。在吸收条的垂直方向上，在 0.2-0.5 个周期/毫米处出现一个峰值，并且从大约 1 个周期/毫米开始是一个恒定值；而在平行方向上是一个相对于空间频率变化的恒定值。它表明可用于准确描述不同成像条件下网格的特性。我们相信，使用建议的索引可以扩展使用网格时优化成像条件的选项。