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Lubberts effect in columnar phosphors.

机译：Lubberts效应在柱状磷光体中。

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摘要

Noise transfer in granular x-ray imaging phosphor screens is not proportional to the square of the magnitude of the signal transfer when the transfer properties are considered for the entire screen thickness, unless appropriately weighted at each depth of interaction. This property, known as the Lubberts effect, has not yet been studied in columnar structured screens because of a lack of a generalized description of the depth-dependent light transport. In this paper, we investigate the signal and noise transfer characteristics of columnar phosphors used in digital mammography detectors using DETECT-II, an optical Monte Carlo light transport simulation code. We first validate our choice of optical parameters for the description of granular and columnar screens using published normalized modulation transfer (MTF) experimental data. Our calculations of MTF match empirically measured MTFs for a granular film/screen analog system, and for an indirect x-ray digital imaging system with CsI:Tl screen representative of digital mammography systems. Using the depth-dependent spread functions and collection efficiencies, we calculate the signal and noise transfer functions and the Lubberts fraction, which is the ratio of the signal transfer function to the noise transfer function, for different screen thicknesses of granular and columnar phosphors. We find that the Lubberts fraction of a 85 microm granular screen model corresponding to a Gd2O2S:Tb screen is similar to the fraction for a 100 microm columnar CsI:Tl screen.
机译：当考虑到整个屏幕厚度的传递特性时，颗粒X射线成像荧光粉屏幕中的噪声传递与信号传递幅度的平方不成比例，除非在每个交互作用深度进行适当加权。由于缺乏对深度相关的光传输的一般描述，尚未在柱状结构的屏幕中研究这种称为Lubberts效应的特性。在本文中，我们使用光学蒙特卡罗光传输模拟代码DETECT-II，研究了用于数字乳腺X线摄影探测器中的柱状磷光体的信号和噪声传输特性。我们首先使用已发布的归一化调制传输（MTF）实验数据来验证用于描述颗粒和柱状屏幕的光学参数选择。我们的MTF计算与颗粒胶片/屏幕模拟系统以及具有CsI：Tl屏幕代表数字乳房X线照相系统的间接X射线数字成像系统的经验测得的MTF相匹配。使用与深度有关的扩散函数和收集效率，我们计算了颗粒和柱状磷光体不同屏幕厚度下的信号和噪声传递函数以及Lubberts分数，即信号传递函数与噪声传递函数的比值。我们发现对应于Gd2O2S：Tb屏幕的85微米颗粒筛模型的Lubberts分数类似于100微米柱状CsI：Tl筛的分数。

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