MAXIMUM-LIKELIHOOD POSITIONING IN THE SCINTILLATION CAMERA USING DEPTH OF INTERACTION
MAXIMUM-LIKELIHOOD POSITIONING IN THE SCINTILLATION CAMERA USING DEPTH OF INTERACTION
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DOI：
10.1109/42.222673
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发表时间：
1993-03-01
影响因子：
10.6
通讯作者：
OLIVIER, P
中科院分区：
文献类型：
--
作者：
GAGNON, D;POULIOT, N;OLIVIER, P
在过去，已经详细描述了Anger伽马相机中光电倍增管（PM）响应的空间（X和Y）依赖性。光分布到单个PM在伽马相机中的立体角看到的每个光电阴极是一个真正的三维问题，相互作用的深度（DOI）必须包括在PM输出的分析。此外，DOI是一个随机过程，必须在逐个事件的基础上明确考虑，同时评估位置和能量。已经量化了DOI对PM响应的具体影响。该方法的实施和测试的Monte Carlo模拟器，特别照顾的噪声建模。开发了两个模型，第一个模型只考虑相机的几何方面，用于比较，第二个模型描述了一个更真实的相机环境。在一个典型的相机配置和140 keV的光子，DOI单独可以占6.4毫米的位置差异和12%的能量之间的两个闪烁。当光子不垂直进入晶体时，例如在斜孔、锥形光束和其他聚焦准直器中，DOI的变化仍然会带来额外的失真。对于0.95 cm的晶体和30度的倾斜角，折射率因子可以导致事件位置的5.5 mm变化。结果表明，几何和随机效应的DOI肯定会降低相机的性能，并应包括在图像形成过程中。
The spatial (X and Y) dependence of the photomultiplier (PM) response in Anger gamma camera has been thoroughly described in the past. The light distribution to individual PM in gamma cameras-solid angle seen by each photocathode-being a truly three-dimensional problem, the depth of interaction (DOI) has to be included in the analysis of the PM output. Furthermore, DOI being a stochastic process, it has to be considered explicitly, on a event-by-event basis, while evaluating both position and energy. Specific effects of the DOI on the PM response have been quantified. The method was implemented and tested on a Monte Carlo simulator with special care to the noise modelling. Two models were developed, a first one considering only the geometric aspects of the camera and used for comparison, and a second one describing a more realistic camera environment. In a typical camera configuration and 140 keV photons, the DOI alone can account for a 6.4 mm discrepancy in position and 12% in energy between two scintillations. Variation of the DOI can still bring additional distortions when photons do not enter the crystal perpendicularly such as in slant hole, cone beam and other focusing collimators. With a 0.95 cm crystal and a 30-degrees slant angle, the obliquity factor can be responsible for a 5.5 mm variation in the event position. Results indicate that both geometrical and stochastic effects of the DOI are definitely reducing the camera performances and should be included in the image formation process.