Siewerdsen J H, Antonuk L E, el-Mohri Y, Yorkston J, Huang W, Cunningham I A
Department of Radiation Oncology, University of Michigan Medical Center, Ann Arbor 48109, USA.
Med Phys. 1998 May;25(5):614-28. doi: 10.1118/1.598243.
The performance of an indirect-detection, active matrix flat-panel imager (FPI) at diagnostic energies is reported in terms of measured and theoretical signal size, noise power spectrum (NPS), and detective quantum efficiency (DQE). Based upon a 1536 x 1920 pixel, 127 microns pitch array of a-Si:H thin-film transistors and photodiodes, the FPI was developed as a prototype for examination of the potential of flat-panel technology in diagnostic x-ray imaging. The signal size per unit exposure (x-ray sensitivity) was measured for the FPI incorporating five commercially available Gd2O2S:Tb converting screens at energies 70-120 kVp. One-dimensional and two-dimensional NPS and DQE were measured for the FPI incorporating three such converters and as a function of the incident exposure. The measurements support the hypothesis that FPIs have significant potential for application in diagnostic radiology. A cascaded systems model that has shown good agreement with measured individual pixel signal and noise properties is employed to describe the performance of various FPI designs and configurations under a variety of diagnostic imaging conditions. Theoretical x-ray sensitivity, NPS, and DQE are compared to empirical results, and good agreement is observed in each case. The model is used to describe the potential performance of FPIs incorporating a recently developed, enhanced array that is commercially available and has been proposed for testing and application in diagnostic radiography and fluoroscopy. Under conditions corresponding to chest radiography, the analysis suggests that such systems can potentially meet or even exceed the DQE performance of existing technology, such as screen-film and storage phosphor systems; however, under conditions corresponding to general fluoroscopy, the typical exposure per frame is such that the DQE is limited by the total system gain and additive electronic noise. The cascaded systems analysis provides a valuable means of identifying the limiting stages of the imaging system, a tool for system optimization, and a guide for developing strategies of FPI design for various imaging applications.
本文根据测量和理论信号大小、噪声功率谱（NPS）以及探测量子效率（DQE），报告了间接探测有源矩阵平板成像器（FPI）在诊断能量下的性能。基于一个1536×1920像素、像素间距为127微米的非晶硅氢化薄膜晶体管和光电二极管阵列，该FPI被开发为一个原型，用于研究平板技术在诊断X射线成像中的潜力。在70 - 120 kVp能量下，对包含五种市售Gd2O2S:Tb转换屏的FPI测量了每单位曝光的信号大小（X射线灵敏度）。对包含三种此类转换器的FPI，测量了一维和二维NPS以及DQE，并将其作为入射曝光的函数。这些测量结果支持了FPI在诊断放射学中有显著应用潜力的假设。采用一种与测量的单个像素信号和噪声特性显示出良好一致性的级联系统模型，来描述各种FPI设计和配置在各种诊断成像条件下的性能。将理论X射线灵敏度、NPS和DQE与实验结果进行比较，在每种情况下都观察到了良好的一致性。该模型用于描述包含一种最近开发的增强型阵列的FPI的潜在性能，这种阵列已商业化，并且已被提议用于诊断放射摄影和荧光透视的测试和应用。在对应于胸部X线摄影的条件下，分析表明此类系统有可能达到甚至超过现有技术（如屏 - 片和存储磷光体系统）的DQE性能；然而，在对应于一般荧光透视的条件下，每帧的典型曝光使得DQE受到整个系统增益和附加电子噪声的限制。级联系统分析提供了一种识别成像系统限制阶段的有价值方法、一种系统优化工具以及一种为各种成像应用开发FPI设计策略的指南。
