Simulation of light transport in scintillators based on 3D characterization of crystal surfaces.
Simulation of light transport in scintillators based on 3D characterization of crystal surfaces.
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DOI：
10.1088/0031-9155/58/7/2185
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发表时间：
2013-04-07
影响因子：
3.5
通讯作者：
Cherry SR
中科院分区：
文献类型：
--
作者：
Roncali E;Cherry SR
在正电子发射断层扫描(PET)探测器的开发中，了解和优化闪烁体的光收集对于实现高性能至关重要，特别是当设计结合了相互作用深度(DOI)编码或飞行时间信息时。蒙特卡罗模拟在指导探测器设计的研究中发挥着重要作用，现在流行的软件，如GATE，已经包括了闪烁体中光传输的模型。尽管目前的模拟工具包能够提供完美抛光表面的准确模型，但它们不能成功地预测其他表面光洁度的光输出，例如那些经常用于DOI编码检测器的表面光洁度。这些模型的精度不足主要源于将粗糙表面简化为由其正态分布(通常为高斯分布)确定的微小面集合。用户可以指定该分布的标准偏差，但该参数不能提供表面反射特性的完整描述。我们提出了一种不同的方法，基于原子力显微镜(AFM)对表面的3D测量。对抛光和粗糙(未抛光)晶体进行扫描，以计算表面反射特性。计算反射率和反射光的角度分布，并将其存储在查找表(LUT)中。LUT考虑了入射角的影响，并被积分到光传输模型中。对不同尺寸的晶体分别进行了有无反射镜的模拟。模拟的最大光输出和光输出随DOI的变化与晶体的实验表征非常一致，表明我们的方法提供了一个精确的抛光和粗糙表面模型，可以用来预测闪烁体中的光收集。该模型基于表面的真实3D表示，对表面没有任何假设，并提供了对粗糙晶体的光学行为的洞察，这对优化PET探测器的设计起到了至关重要的作用。该方法也与现有的仿真工具包兼容，下一步包括在GATE中实现。
In the development of positron emission tomography (PET) detectors, understanding and optimizing scintillator light collection is critical for achieving high performance, particularly when the design incorporates depth-of-interaction (DOI) encoding or time-of-flight information. Monte-Carlo simulations play an important role in guiding research in detector designs and popular software such as GATE now include models of light transport in scintillators. Although current simulation toolkits are able to provide accurate models of perfectly polished surfaces, they do not successfully predict light output for other surface finishes, for example those often used in DOI-encoding detectors. The lack of accuracy of those models mainly originates from a simplified description of rough surfaces as an ensemble of micro-facets determined by the distribution of their normal, typically a Gaussian distribution. The user can specify the standard deviation of this distribution, but this parameter does not provide a full description of the surface reflectance properties. We propose a different approach based on 3D measurements of the surface using atomic force microscopy (AFM). Polished and rough (unpolished) crystals were scanned to compute the surface reflectance properties. The angular distributions of reflectance and reflected rays were computed and stored in look-up tables (LUTs). The LUTs account for the effect of incidence angle and were integrated in a light transport model. Crystals of different sizes were simulated with and without reflector. The simulated maximum light output and the light output as a function of DOI showed very good agreement with experimental characterization of the crystals, indicating that our approach provides an accurate model of polished and rough surfaces and could be used to predict light collection in scintillators. This model is based on a true 3D representation of the surface, makes no assumption about the surface and provides insight on the optical behaviour of rough crystals that can play a critical role in optimizing the design of PET detectors. This approach is also compatible with existing simulation toolkits and next steps include the implementation in GATE.
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影响因子：
3.5
作者：
Spanoudaki, V. Ch;Levin, C. S.
通讯作者：
Levin, C. S.
影响因子：
1.8
作者：
Shao, Y;Meadors, K;Cherry, SR
通讯作者：
Cherry, SR
影响因子：
3.5
作者：
van der Laan, D. J. (Jan);Schaart, Dennis R.;van Eijk, Carel W. E.
通讯作者：
van Eijk, Carel W. E.
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：
Rothfuss, H;Casey, M;Schmand, M
通讯作者：
Schmand, M