Temporal performance of amorphous selenium mammography detectors
Temporal performance of amorphous selenium mammography detectors
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DOI：
10.1118/1.1827791
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发表时间：
2005-01-01
期刊：
影响因子：
3.8
通讯作者：
Zhao, W
中科院分区：
文献类型：
--
作者：
Zhao, B;Zhao, W
我们研究了专为乳腺摄影成像设计的非晶硒（a-Se）探测器的时间性能。我们的目标是量化作为成像条件的函数的固有滞后和重影的a-Se光电导体。两个小面积电极的a-Se样品，一个正，另一个负偏置的入射侧的X射线，被用于实验中。通过在不同电场强度E-Se下向样品递送如在筛查乳房X线摄影中经历的多个原始曝光，同时测量通过a-Se样品的电流，来进行滞后和重影的研究。将不同操作条件下的重影定量为与照射前相比的X射线灵敏度（从样品测量的X射线产生的光电流）降低的百分比。通过在每次X射线曝光结束后的给定时间测量a-Se的残余电流来确定滞后。滞后和重影作为E-Se和累积暴露的函数进行测量。在我们的实验中使用的E-se的值范围从1到20 V /妈妈。有人发现，重影增加与曝光和减少与E-se的两个样品，因为捕获的电子和X射线产生的空穴之间的复合的主导效应。另一方面，滞后对E-se和累积暴露具有不同的依赖性。在E-Se小于或等于10 V /μ m时，两个样品的第一帧滞后随累积曝光缓慢变化，正偏置样品的范围为0.2%-1.7%，负偏置样品的范围为0.5%-8%。总的来说，由于捕获电子的密度较低，正偏置样本比负偏置样本具有更好的时间性能。曝光之间的时间间隔的时间性能的影响也进行了研究。在较长的时间间隔内观察到重影的恢复，这归因于通过暗电流注入的空穴对捕获电子的中和作用。(C)2005年美国医学物理学家协会。
We investigated temporal performance of amorphous selenium (a-Se) detectors specifically designed for mammographic imaging. Our goal is to quantify the inherent lag and ghosting of a-Se photoconductor as a function of imaging conditions. Two small area electroded a-Se samples, one positively and the other negatively biased on the entrance side of x rays, were used in the experiments. The study of lag and ghosting was performed by delivering a number of raw exposures as experienced in screening mammography to the samples at different electric field strength E-Se while measuring the current through the a-Se sample. Ghosting at different operational conditions was quantified as the percentage x-ray sensitivity (x-ray generated photocurrent measured from the sample) reduction compared to before irradiation. Lag was determined by measuring the residual current of a-Se at a given time after the end of each x-ray exposure. Both lag and ghosting were measured as a function of E-Se and cumulative exposure. The values of E-se used in our experiments ranged from 1 to 20 V /mum. It was found that ghosting increases with exposure and decreases with E-se for both samples because of the dominant effect of recombination between trapped electrons and x-ray generated holes. Lag on the other hand has different dependence on E-se and cumulative exposure. At E-Se less than or equal to 10 V / mum, the first frame lag for both samples changed slowly with cumulative exposure, with a range of 0.2%-1.7% for the positively biased sample and 0.5%-8% for the negatively biased sample. Overall the positively biased sample has better temporal performance than the negatively biased sample due to the lower density of trapped electrons. The impact of time interval between exposures on the temporal performance was also investigated. Recovery of ghosting with longer time interval was observed, which was attributed to the neutralization of trapped electrons by injected holes through dark current. (C) 2005 American Association of Physicists in Medicine.