The timing resolution of scintillation-detector systems: Monte Carlo analysis.
The timing resolution of scintillation-detector systems: Monte Carlo analysis.
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DOI：
10.1088/0031-9155/54/21/004
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发表时间：
2009-11-07
影响因子：
3.5
通讯作者：
Choong WS
中科院分区：
文献类型：
--
作者：
Choong WS
快速闪烁材料和快速光电倍增管 (PMT) 的最新进展激发了人们对飞行时间 (TOF) 正电子发射断层扫描 (PET) 的新兴趣。众所周知，PET 中时序分辨率的提高可以显着降低重建图像中的噪声方差，从而提高图像质量。为了评估 TOF PET 中使用的闪烁探测器的定时性能，我们使用蒙特卡洛分析对物理过程（晶体几何形状、晶体表面光洁度、闪烁体上升时间、闪烁体衰减时间、光电子产额、PMT 渡越时间扩展、PMT 单电子响应、放大器响应和时间拾取方法）进行建模，这些过程有助于闪烁探测器系统的定时分辨率。在蒙特卡罗分析中，光电子发射通过速率函数建模，用于生成光电子时间点。使用 Geant4 模拟的速率函数表示闪烁体的固有光发射和随后通过晶体的光传输的组合。 PMT 输出信号由光电子发射产生的 PMT 单电子响应的叠加决定。分析中对 PMT 的渡越时间扩展和单电子增益变化进行了建模。分析中考虑了三种实用的时间选取方法。从统计上看，最佳的定时分辨率是通过第一次光电子定时实现的。计算出的时序分辨率表明，前沿鉴别器比恒定分数鉴别器提供更好的时序性能，并且在使用 2 阈值或 3 阈值鉴别器时产生可比较的结果。对于典型的 PMT，探测器噪声对定时分辨率的影响可以忽略不计。发现计算的时间分辨率随着平均光电子产率的增加、闪烁体衰减时间的减少和渡越时间扩展的减少而提高。然而，如果第一光电子定时小于渡越时间扩展，则仅通过改进的渡越时间扩展获得定时分辨率的实质性改进。虽然计算出的计时性能似乎不受晶体像素尺寸的影响，但与抛光晶体相比，蚀刻晶体的计时性能有所提高。此外，计算出的定时分辨率会随着晶体长度的增加而降低。这些观察结果可以通过研究初始光电子速率来解释。实验测量与计算的定时分辨率相当吻合。这项工作中开发的蒙特卡罗分析将使我们能够优化闪烁探测器的计时并了解限制其性能的物理因素。
Recent advancements in fast scintillating materials and fast photomultiplier tubes (PMTs) have stimulated renewed interest in time-of-flight (TOF) positron emission tomography (PET). It is well known that the improvement in the timing resolution in PET can significantly reduce the noise variance in the reconstructed image resulting in improved image quality. In order to evaluate the timing performance of scintillation detectors used in TOF PET, we use a Monte Carlo analysis to model the physical processes (crystal geometry, crystal surface finish, scintillator rise time, scintillator decay time, photoelectron yield, PMT transit time spread, PMT single-electron response, amplifier response, and time pick-off method) that can contribute to the timing resolution of scintillation-detector systems. In the Monte Carlo analysis, the photoelectron emissions are modeled by a rate function, which is used to generate the photoelectron time points. The rate function, which is simulated using Geant4, represents the combined intrinsic light emissions of the scintillator and the subsequent light transport through the crystal. The PMT output signal is determined by the superposition of the PMT single-electron response resulting from the photoelectron emissions. The transit time spread and the single-electron gain variation of the PMT are modeled in the analysis. Three practical time pick-off methods are considered in the analysis. Statistically, the best timing resolution is achieved with the first photoelectron timing. The calculated timing resolution suggests that a leading edge discriminator gives better timing performance than a constant fraction discriminator and produces comparable results when a 2-threshold or 3-threshold discriminator is used. For a typical PMT, the effect of detector noise on the timing resolution is negligible. The calculated timing resolution is found to improve with increasing mean photoelectron yield, decreasing scintillator decay time, and decreasing transit time spread. However, only substantial improvement in the timing resolution is obtained with improved transit time spread if the first photoelectron timing is less than the transit time spread. While the calculated timing performance does not seem to be affected by the pixel size of the crystal, it improves for an etched crystal compared to a polished crystal. In addition, the calculated timing resolution degrades with increasing crystal length. These observations can be explained by studying the initial photoelectron rate. Experimental measurements provide reasonably good agreement with the calculated timing resolution. The Monte Carlo analysis developed in this work will allow us to optimize the scintillation detectors for timing and to understand the physical factors limiting their performance.
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影响因子：
1.8
作者：
DORENBOS, P;DEHAAS, JTM;SCHWEITZER, JS
通讯作者：
SCHWEITZER, JS
影响因子：
1.8
作者：
Valentine, JD;Rooney, BD;Li, J
通讯作者：
Li, J
影响因子：
1.8
作者：
MELCHER, CL;SCHWEITZER, JS
通讯作者：
SCHWEITZER, JS
影响因子：
1.8
作者：
BINKLEY, DM
通讯作者：
BINKLEY, DM
DOI：
10.1016/j.nima.2006.10.291
发表时间：
2007-03-01
影响因子：
1.4
作者：
Va'vra, J.;Benitez, J.;Schwiening, J.
通讯作者：
Schwiening, J.