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Development of a Portable Instrument for Automated Measurements of the Detective Quantum Efficiency of X-Ray Detectors

机译:用于自动测量X射线探测器的探测量子效率的便携式仪器的开发

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The scientific community has generally adopted use of the modulation transfer function (MTF) and detective quantum efficiency (DQE) as primary measures of performance of radiographic detectors. However, measurement of these parameters is generally restricted to experts in laboratory environments due to the required x-ray physics knowledge, specialized instrumentation and computational analyses. We have developed a prototype instrument that automates both the physical measurement and subsequent image analysis to determine the MTF, noise power spectrum (NPS) and DQE of radiographic and mammographic systems. The instrument is placed in the x-ray path directly in front of the detector. A series of images are acquired, saved in "raw" DICOM format and then used to determine the MTF (using the slanted-edge method) and NPS. The number of incident quanta is calculated from measurements of the incident exposure including corrections for air temperature and pressure and ionization chamber spectral response. The primary sources of error are backscatter from the detector and scatter generated within the instrument. These have been minimized to achieve an incident exposure measurement within 2% of a calibrated electrometer and chamber in free space. The MTF and DQE of a commercial Csl-based flat-panel detector were measured over a range of incident exposures from 20 uR to 20 mR per image. Results agreed with both our own laboratory measurements and previously published measurements performed elsewhere with a similar detector within 2% for the MTF and 5% for the DQE. A complete DQE analysis of a clinical digital flat-panel detector is completed in 30 minutes and requires no system modifications.
机译:科学界普遍采用调制传递函数(MTF)和探测量子效率(DQE)作为射线照相探测器性能的主要指标。但是,由于所需的X射线物理知识,专用仪器和计算分析,这些参数的测量通常仅限于实验室环境中的专家。我们开发了一种原型仪器,可以自动进行物理测量和随后的图像分析,以确定射线照相和X线照相系统的MTF,噪声功率谱(NPS)和DQE。仪器被放置在检测器正前方的X射线路径中。采集一系列图像,以“原始” DICOM格式保存,然后用于确定MTF(使用斜边方法)和NPS。入射量子的数量是根据对入射暴露的测量得出的,包括对空气温度和压力以及电离室光谱响应的校正。误差的主要来源是检测器的反向散射和仪器内部产生的散射。这些已被最小化,以实现在自由空间中经过校准的静电计和室的2%之内的入射曝光测量。在每张图像20 uR至20 mR的入射曝光范围内,测量了商用Csl基平板探测器的MTF和DQE。结果与我们自己的实验室测量结果和先前在其他地方进行的测量结果一致,MTF在2%之内,DQE在5%之内。在30分钟内即可完成对临床数字平板探测器的完整DQE分析,而无需修改系统。

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