X-ray imaging using avalanche multiplication in amorphous selenium: investigation of depth dependent avalanche noise.
X-ray imaging using avalanche multiplication in amorphous selenium: investigation of depth dependent avalanche noise.
复制标题
在非晶硒中使用雪崩倍增的 X 射线成像：深度相关雪崩噪声的研究。
DOI：
10.1118/1.2437097
复制
发表时间：
2007
期刊：
影响因子：
3.8
通讯作者：
Rowlands,JA
中科院分区：
文献类型：
--
作者：
Hunt,DC;Tanioka,Kenkichi;Rowlands,JA
在过去的十年中，平板探测器（FPD）（也称为有源矩阵平板成像器）在数字X射线摄影中得到了迅速发展。这项新技术适用于其他模式，如荧光透视，需要采集多个图像，但可以从一些改进中受益。在获取多于一个图像的这种应用中，较少的辐射可用于形成每个图像，并且放大器噪声成为严重的问题。非晶硒中的雪崩倍增可以在读出之前提供必要的放大，以便减少FPD的电子噪声的影响。然而，在直接转换探测器中，雪崩倍增会导致一种新的增益波动噪声源，称为深度相关雪崩噪声。建立了一个理论模型来理解深度依赖的雪崩噪声。在一个实现雪崩倍增的直接成像系统上进行了实验，以验证理论。对于适合于用于荧光透视的诊断成像FPD的参数，发现探测量子效率（DQE）随着电场的增加而下降多达50%，如理论模型所预测的。DQE的这种下降可以通过分离收集区和雪崩区来消除。例如，通过具有低电场区域，其中X射线被吸收并转换成电荷，然后漂移到高电场区域，其中X射线产生的电荷经历雪崩倍增。这意味着用于低曝光成像技术的量子噪声限制的直接转换FPD是可能的。
The past decade has seen the swift development of the flat‐panel detector (FPD), also known as the active matrix flat‐panel imager, for digital radiography. This new technology is applicable to other modalities, such as fluoroscopy, which require the acquisition of multiple images, but could benefit from some improvements. In such applications where more than one image is acquired less radiation is available to form each image and amplifier noise becomes a serious problem. Avalanche multiplication in amorphous selenium can provide the necessary amplification prior to read out so as to reduce the effect of electronic noise of the FPD. However, in direct conversion detectors avalanche multiplication can lead to a new source of gain fluctuation noise called depth dependent avalanche noise. A theoretical model was developed to understand depth dependent avalanche noise. Experiments were performed on a direct imaging system implementing avalanche multiplication in a layer of to validate the theory. For parameters appropriate for a diagnostic imaging FPD for fluoroscopy the detective quantum efficiency (DQE) was found to drop by as much as 50% with increasing electric field, as predicted by the theoretical model. This drop in DQE can be eliminated by separating the collection and avalanche regions. For example by having a region of low electric field where x rays are absorbed and converted into charge that then drifts into a region of high electric field where the x‐ray generated charge undergoes avalanche multiplication. This means quantum noise limited direct conversion FPD for low exposure imaging techniques are a possibility.