Spatial frequency-dependent pulse-height spectrum and method for analyzing detector DQE(f) from ensembles of single X-ray images.
Spatial frequency-dependent pulse-height spectrum and method for analyzing detector DQE(f) from ensembles of single X-ray images.
复制标题
用于从单个 X 射线图像集合中分析探测器 DQE(f) 的空间频率相关脉冲高度谱和方法。
DOI：
10.1002/mp.15344
复制
发表时间：
2022
期刊：
影响因子：
3.8
通讯作者：
Zhao,Wei
中科院分区：
文献类型：
--
作者：
Dow,Scott;Howansky,Adrian;Lubinsky,AnthonyR;Zhao,Wei
能量积分探测器（EID）中使用的闪烁体和光电导体由于X射线能量沉积和二次量子产生和传输的变化而对单次探测X射线的成像响应存在固有变化，这会降低DQE（f）。可以使用单次X射线成像（SXI）实验记录和研究X射线放大器对单次X射线的成像响应;但是，目前还没有将SXI实验结果与EID DQE（f）相关联的方法。这项工作提出了一个通用的分析框架，用于计算和分析的DQE（f）性能的EID从单个X射线图像ensemble.MethodsA空间频率（f）相关的增益，从一个单一的X射线检测的成像响应的傅立叶变换的EID的脉冲高度spectrum.MethodsA空间频率（f）相关的增益，被定义为。Af相关脉冲高度谱定义为复平面上的2D概率密度函数。 用于定义af依赖的Swank因子AS（f），其完全表征由于单个X射线噪声引起的DQE（f）退化。分析AS（f）由于Swank噪声、频率依赖衰减的变化以及由于每个单X射线成像响应中的不对称性的变化而发生的噪声而导致的退化。模拟了三个示例成像系统，以证明远程能量沉积和有限数量的次级量子中的深度相关变化对AS（f）、MTF（f）和Δ S（f）/Δ S（0）的影响，这些影响是从单个X射线图像的集合计算的。这一点也通过模拟真实的成像系统来证明;即基于Gd2O2S的EID。使用后者的成像系统，AS（f）估计的收敛性作为检测到的X射线每ensemble.ResultsDepth依赖的变化导致AS（f）退化完全是由于深度依赖的光学Swank噪声和Lubberts效应的函数进行调查。相反，大部分的AS（f）的退化所造成的远程能量沉积和有限的二次量子发生由于变化。当使用低于Gd K边缘的输入X射线能量时，频率依赖性衰减的变化占基于GOS的EID中AS（f）退化的大部分，并且观察到非常小的Swank噪声和变化。然而，在K边缘以上，由于Swank噪声和变化而导致的AS（f）退化大大增加。收敛的AS（f）的变化是有限的;成像系统的变化，需要更多的检测X射线perensemble.ConclusionsAn分析框架，提出了推广的脉冲高度谱和Swank因子arbitaryf。单个X射线噪声源（如吕伯特效应、远程能量沉积和有限次级量子）对探测器性能的影响可以使用AS（f）表示和量化。该方法可用于从单个X射线图像的集合中计算MTF（f）、DQE（f）和DQE（f），并提供了一种分析拟议EID设计的额外工具。
PurposeScintillators and photoconductors used in energy integrating detectors (EIDs) have inherent variations in their imaging response to single‐detected X‐rays due to variations in X‐ray energy deposition and secondary quanta generation and transport, which degrades DQE(f). The imaging response of X‐ray scintillators to single X‐rays may be recorded and studied using single X‐ray imaging (SXI) experiments; however, no method currently exists for relating SXI experimental results to EID DQE(f). This work proposes a general analytical framework for computing and analyzing the DQE(f) performance of EIDs from single X‐ray image ensembles using a spatial frequency‐dependent pulse‐height spectrum.MethodsA spatial frequency (f)‐dependent gain, , is defined as the Fourier transform of the imaging response of an EID to a single‐detected X‐ray. Af‐dependent pulse‐height spectrum, , is defined as the 2D probability density function of over the complex plane. is used to define af‐dependent Swank factor, AS(f), which fully characterizes the DQE(f) degradation due to single X‐ray noise. AS(f) is analyzed in terms of its degradation due to Swank noise, variations in the frequency‐dependent attenuation of , and noise in which occurs due to variations in the asymmetry in each single X‐ray's imaging response. Three example imaging systems are simulated to demonstrate the impact of depth‐dependent variation in , remote energy deposition, and a finite number of secondary quanta, on , AS(f), MTF(f), and NPS(f)/NPS(0), which are computed from ensembles of single X‐ray images. The same is also demonstrated by simulating a realistic imaging system; that is, a Gd2O2S‐based EID. Using the latter imaging system, the convergence of AS(f) estimates is investigated as a function of the number of detected X‐rays per ensemble.ResultsDepth‐dependent variation resulted in AS(f) degradation exclusively due to depth‐dependent optical Swank noise and the Lubberts effect. Conversely, the majority of AS(f) degradation caused by remote energy deposition and finite secondary quanta occurred due to variations in . When using input X‐ray energies below the K‐edge of Gd, variations in the frequency‐dependent attenuation of accounted for the majority of AS(f) degradation in the GOS‐based EID, and very little Swank noise and variations in were observed. Above the K‐edge, however, AS(f) degradation due to Swank noise and variations in greatly increased. The convergence of AS(f) was limited by variation in ; imaging systems with more variation in required more detected X‐rays per ensemble.ConclusionsAn analytical framework is proposed that generalizes the pulse‐height spectrum and Swank factor to arbitraryf. The impact of single X‐ray noise sources, such as the Lubberts effect, remote energy deposition, and finite secondary quanta on detector performance, may be represented using , and quantified using AS(f). The approach may be used to compute MTF(f), NPS(f), and DQE(f) from ensembles of single X‐ray images and provides an additional tool to analyze proposed EID designs.