The influence of electron multiplication and internal X-ray fluorescence on the performance of a scintillator-based gamma camera-猫眼课题宝

电子倍增和内部 X 射线荧光对闪烁体伽马相机性能的影响

DOI：

10.1016/j.nima.2012.03.013

发表时间：

2012

期刊：

Accelerators, Spectrometers, Detectors and Associated Equipment

影响因子：

通讯作者：

中科院分区：

文献类型：

作者：

Hall D

当考虑“标准”伽马相机时，人们可能会想象一个光电倍增管阵列或类似的小面积探测器阵列。成像探测器的该阵列将被附接到闪烁体模块的对应阵列（或闪烁体的固体层），以便在感兴趣的能量区域（通常为8- 140 keV）中给出高探测效率。近年来，能够实现高得多的空间分辨率的伽马相机的发展已经导致了一系列新的基于电荷耦合器件的系统，其在闪烁体和CCD之间具有某种形式的信号倍增，以便人们在CCD噪声之上区分来自闪烁体的光输出。电子倍增电荷耦合器件（EM-CCD）的使用通过“碰撞电离”的形式将增益过程并入CCD内，然而，由于碰撞电离的概率性质，增益过程引入了“过量噪声因子”，并且该额外噪声因此对探测器的空间和光谱分辨率产生影响。闪烁体中的内部荧光产生K壳层X射线荧光光子，其可以与入射伽马射线一起被检测到，也对伽马相机的成像能力具有重大影响。这种影响从低空间分辨率到高空间分辨率相机系统显著变化。通过一个过程的模拟和实验测试集中在高空间分辨率（EM-CCD为基础）的变种，影响伽马相机系统的性能的因素进行了讨论，其结果导致重要的结论，要考虑未来系统的发展。本文提出了一种研究的影响的EM-CCD的增益过程和内部的X射线荧光闪烁体上的性能闪烁器为基础的伽马相机（CCD为基础的或其他），利用Monte Carlo模拟来证明所涉及的方面，它们对成像系统的影响和假设先前讨论的实验研究。

When considering the ‘standard’ gamma-camera, one might picture an array of photo-multiplier tubes or a similar array of small-area detectors. This array of imaging detectors would be attached to a corresponding array of scintillator modules (or a solid layer of scintillator) in order to give a high detection efficiency in the energy region of interest, usually 8–140keV. Over recent years, developments of gamma-cameras capable of achieving much higher spatial resolutions have led to a new range of systems based on Charge-Coupled Devices with some form of signal multiplication between the scintillator and the CCD in order for one to distinguish the light output from the scintillator above the CCD noise. The use of an Electron-Multiplying Charge-Coupled Device (EM-CCD) incorporates the gain process within the CCD through a form of ‘impact ionisation’, however, the gain process introduces an ‘excess noise factor’ due to the probabilistic nature of impact ionisation and this additional noise consequently has an impact on the spatial and spectral resolution of the detector. Internal fluorescence in the scintillator, producing K-shell X-ray fluorescence photons that can be detected alongside the incident gamma-rays, also has a major impact on the imaging capabilities of gamma-cameras. This impact varies dramatically from the low spatial resolution to high spatial resolution camera system. Through a process of simulation and experimental testing focussed on the high spatial resolution (EM-CCD based) variant, the factors affecting the performance of gamma-camera systems are discussed and the results lead to important conclusions to be considered for the development of future systems. This paper presents a study into the influence of the EM-CCD gain process and the internal X-ray fluorescence in the scintillator on the performance of scintillator-based gamma cameras (CCD-based or otherwise), making use of Monte Carlo simulations to demonstrate the aspects involved, their influence on the imaging system and the hypotheses previously discussed in experimental studies.