Servizio Fisica Sanitarìa, Azienda USL di Modena, 41100 Modena, Italy.
Med Phys. 2010 Feb;37(2):440-8. doi: 10.1118/1.3284539.
In this study, five different units based on three different technologies-traditional computed radiography (CR) units with granular phosphor and single-side reading, granular phosphor and dual-side reading, and columnar phosphor and line-scanning reading-are compared in terms of physical characterization and contrast detail analysis.
The physical characterization of the five systems was obtained with the standard beam condition RQA5. Three of the units have been developed by FUJIFILM (FCR ST-VI, FCR ST-BD, and FCR Velocity U), one by Kodak (Direct View CR 975), and one by Agfa (DX-S). The quantitative comparison is based on the calculation of the modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). Noise investigation was also achieved by using a relative standard deviation analysis. Psychophysical characterization is assessed by performing a contrast detail analysis with an automatic reading of CDRAD images.
The most advanced units based on columnar phosphors provide MTF values in line or better than those from conventional CR systems. The greater thickness of the columnar phosphor improves the efficiency, allowing for enhanced noise properties. In fact, NPS values for standard CR systems are remarkably higher for all the investigated exposures and especially for frequencies up to 3.5 lp/mm. As a consequence, DQE values for the three units based on columnar phosphors and line-scanning reading, or granular phosphor and dual-side reading, are neatly better than those from conventional CR systems. Actually, DQE values of about 40% are easily achievable for all the investigated exposures.
This study suggests that systems based on the dual-side reading or line-scanning reading with columnar phosphors provide a remarkable improvement when compared to conventional CR units and yield results in line with those obtained from most digital detectors for radiography.
在这项研究中，我们比较了基于三种不同技术的五种不同的单位，包括传统的基于颗粒磷和单面读取、颗粒磷和双面读取、柱状磷和线扫描读取的计算机射线摄影（CR）单位，比较内容涉及物理特性和对比细节分析。
使用标准光束条件 RQA5 获得了五个系统的物理特性。其中三个单位是由富士胶片公司开发的（FCR ST-VI、FCR ST-BD 和 FCR Velocity U），一个是由柯达公司开发的（Direct View CR 975），一个是由爱克发公司开发的（DX-S）。定量比较是基于调制传递函数（MTF）、噪声功率谱（NPS）和探测量子效率（DQE）的计算。还通过相对标准偏差分析进行了噪声研究。通过对 CDRAD 图像进行自动读取的对比细节分析来评估心理物理特性。
基于柱状磷的最先进的单位提供的 MTF 值与传统 CR 系统相当或更好。柱状磷的较大厚度提高了效率，允许增强噪声特性。事实上，对于所有研究的曝光，标准 CR 系统的 NPS 值都显著更高，尤其是在 3.5 lp/mm 及以下的频率。因此，基于柱状磷和线扫描读取或颗粒磷和双面读取的三个单位的 DQE 值明显优于传统 CR 系统。实际上，对于所有研究的曝光，很容易实现约 40%的 DQE 值。
本研究表明，与传统 CR 系统相比，基于双面读取或线扫描读取的柱状磷系统提供了显著的改进，并产生了与大多数放射摄影用数字探测器相当的结果。
