Wronski M M, Reznik A, Rowlands J A, Zhao W, Segui J A
Imaging Research, Sunnybrook Health Sciences Centre, Toronto, ON.
Department of Radiology, Health Sciences Center, State University of New York at Stony Brook, Stony Brook, NY.
Med Phys. 2008 Jul;35(7Part3):3411-3412. doi: 10.1118/1.2965972.
Digital flat panel detectors are increasingly being used in radiography and fluoroscopy. The imaging performance of current systems, however, is compromised by electronic noise at the low X-ray exposures employed in fluoroscopy and low-dose radiography. In other words, current flat panel detectors are not quantum noise limited at these low radiation exposures. There is thus a need to develop an imaging detector with the high sensitivity of an X-ray image intensifier and the inherent advantages of a solid-state flat panel detector. Towards this end, we have developed and characterized a novel solid-state device capable of providing very high avalanche gains and an excellent temporal response. The device which is based on the amorphous photoconductor a-Se, is scalable (i.e. can be manufactured in large areas), can overcome electronic noise even at the lowest X-ray exposures used in diagnostic imaging (0.1 μR/frame at the detector) and has a very low level of dark current. Here, we investigate the gain and temporal characteristics of this device and discuss its applicability for low exposure X-ray imaging as well as the effects of avalanche gain on the detective quantum efficiency. Coupled to a high-resolution structured CsI X-ray scintillator and a thin film transistor array, this device should provide a true solid-state alternative to the X-ray image intensifier, which is both robust and cost-effective. This should open the door to dose-efficient flat panel imagers for radiography and fluoroscopy as well as a number of other demanding medical imaging applications.
数字平板探测器在放射摄影和荧光透视中越来越多地被使用。然而，当前系统的成像性能在荧光透视和低剂量放射摄影所采用的低X射线曝光条件下会受到电子噪声的影响。换句话说，当前的平板探测器在这些低辐射曝光条件下并非受量子噪声限制。因此，需要开发一种兼具X射线图像增强器的高灵敏度和固态平板探测器固有优势的成像探测器。为此，我们已经开发并表征了一种新型固态器件，它能够提供非常高的雪崩增益和出色的时间响应。该器件基于非晶态光电导体α - 硒，可扩展（即能够大面积制造），即使在诊断成像中使用的最低X射线曝光条件下（探测器处为0.1 μR/帧）也能克服电子噪声，并且暗电流水平非常低。在这里，我们研究该器件的增益和时间特性，并讨论其在低曝光X射线成像中的适用性以及雪崩增益对探测量子效率的影响。与高分辨率结构化碘化铯X射线闪烁体和薄膜晶体管阵列相结合，该器件应能为X射线图像增强器提供一种真正的固态替代方案，既坚固又经济高效。这应为放射摄影和荧光透视的剂量高效平板成像仪以及许多其他苛刻的医学成像应用打开大门。
