Modeling scintillator-photodiodes as detectors for megavoltage CT
Modeling scintillator-photodiodes as detectors for megavoltage CT
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DOI：
10.1118/1.1710733
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发表时间：
2004-05-01
期刊：
影响因子：
3.8
通讯作者：
Rathee, S
中科院分区：
文献类型：
--
作者：
Monajemi, TT;Steciw, S;Rathee, S
研究了钨酸镉 (CdWO4) 和碘化铯 [CsI(Tl)] 闪烁探测器在兆伏计算机断层扫描 (MVCT) 中的使用。已经开发了一个描述从闪烁探测器获取的信号的模型，该模型包含两个步骤：（1）使用 EGSnrc 蒙特卡罗代码计算由于 MeV 光子而沉积在晶体中的能量； (2) 使用光学蒙特卡罗代码 DETECT2000 将晶体体素中生成的光学光子传输到光电二极管。在基部为 0.275 x 0.8 cm(2)、高度为 0.4、1、1.2、1.6 和 2 cm 的单个 CdWO4 和 CsI(Tl) 闪烁晶体中测得的探测器信号通常与模型计算的信号非常一致。构建了一个原型探测器阵列，其中包含 8 个 CdWO4 晶体，每个晶体尺寸为 0.275 x 0.8 x 1 cm(3)，与 16 元件光电二极管阵列接触。测得的 Cobalt-60 光束衰减与固体水厚度的关系呈线性关系。测量了 1.25 MeV 光子（在 Cobalt-60 光束中）的频率相关调制传递函数 [MTF(f)]、噪声功率谱 [NPS(f)] 和探测量子效率 [DQE(f)]。对于 6 MV 光子，仅从直线加速器测量 MTF(f)，其中直线加速器输出中的大脉冲间波动不允许测量 NPS(f)。使用两步蒙特卡罗模拟对探测器的 MTF(f)、NPS(f) 和 DQE(f) 进行建模。对于 1.25 MeV 和 6 MV 光子，探测器阵列的 DQE(0) 分别为 26% 和 19%。对于 1.25 MeV 光子，测量和建模的 MTF(f)、相对 NPS(f) 和 DQE(f) 之间的最大差异分别为 1.5%、1.2% 和 1.9%。对于 6 MV 光束，建模和测量的 MTF(f) 之间的最大差异为 2.5%。该模型足够准确，足以为 MVCT 设计合适的探测器。 (C) 2004 年美国医学物理学家协会。
The use of cadmium tungstate (CdWO4) and cesium iodide [CsI(Tl)] scintillation detectors is studied in megavoltage computed tomography (MVCT). A model describing the signal acquired from a scintillation detector has been developed which contains two steps: (1) the calculation of the energy deposited in the crystal due to MeV photons using the EGSnrc Monte Carlo code; and (2) the transport of the optical photons generated in the crystal voxels to photodiodes using the optical Monte Carlo code DETECT2000. The measured detector signals in single CdWO4 and CsI(Tl) scintillation crystals of base 0.275 x 0.8 cm(2) and heights 0.4, 1, 1.2, 1.6 and 2 cm were, generally, in good agreement with the signals calculated with the model. A prototype detector array which contains 8 CdWO4 crystals, each 0.275 x 0.8 x 1 cm(3), in contact with a 16-element array of photodiodes was built. The measured attenuation of a Cobalt-60 beam as a function of solid water thickness behaves linearly. The frequency dependent modulation transfer function [MTF(f)], noise power spectrum [NPS(f)], and detective quantum efficiency [DQE(f)] were measured for 1.25 MeV photons (in a Cobalt-60 beam). For 6 MV photons, only the MTF(f) was measured from a linear accelerator, where large pulse-to-pulse fluctuations in the output of the linear accelerator did not allow the measurement of the NPS(f). A two-step Monte Carlo simulation was used to model the detector's MTF(f), NPS(f) and DQE(f). The DQE(0) of the detector array was found to be 26% and 19% for 1.25 MeV and 6 MV photons, respectively. For 1.25 MeV photons, the maximum discrepancies between the measured and modeled MTF(f), relative NPS(f) and the DQE(f) were found to be 1.5%, 1.2%, and 1.9%, respectively. For the 6 MV beam, the maximum discrepancy between the modeled and the measured MTF(f) was found to be 2.5%. The modeling is sufficiently accurate for designing appropriate detectors for MVCT. (C) 2004 American Association of Physicists in Medicine.