Spectral method for the correction of the Cerenkov light effect in plastic scintillation detectors: A comparison study of calibration procedures and validation in Cerenkov light-dominated situations
Spectral method for the correction of the Cerenkov light effect in plastic scintillation detectors: A comparison study of calibration procedures and validation in Cerenkov light-dominated situations
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DOI：
10.1118/1.3562896
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发表时间：
2011-04-01
期刊：
影响因子：
3.8
通讯作者：
Beaulieu, Luc
中科院分区：
文献类型：
--
作者：
Guillot, Mathieu;Gingras, Luc;Beaulieu, Luc
目的：本工作的目的是：（1）确定光谱方法是否可以准确地校正塑料闪烁探测器（PSD）中的切伦科夫光效应，以适应切伦科夫光占主导地位的闪烁光的情况;（2）制定准确确定PSD校准因子的程序指南。方法：作者证明，通过使用谱方法的方程，精确校正切伦科夫光效应的条件是两个校准因子的比率必须等于在两个校准因子内测量的切伦科夫光的比率。用于分析的不同光谱区域。基于这一证明，作者提出了两个新的程序来确定PSD的校准因子，这是为了尊重这一条件。通过使用这些新程序和文献中描述的两个参考程序，校准了由圆柱形聚苯乙烯偏振光纤（1.6 mm（3））耦合到塑料光纤组成的PSD。为了验证提取的校准因子，相对剂量分布和输出因子的6 MV光子束从医用直线加速器测量PSD和电离室。重点放在的情况下，切伦科夫光是占主导地位的闪烁光和校准conditions.Results不同的情况下：作者发现，光谱方法的准确性取决于用于确定PSD的校准因子的程序和所使用的光纤的衰减特性。相对剂量分布测量结果表明，光谱法可以校正切伦科夫光效应，精度为1%。所得结果还表明，PSD测量的输出因子低于电离室测量的平方场尺寸大于25 × 25 cm（2），与以前发表的Monte Carlo results.Conclusions：作者的结论是，光谱方法可以用来准确地校正PSD中的切伦科夫光效应。作者证实了最大化校准测量之间的切伦科夫光产生差异的重要性。作者还发现，在光谱方法的原始公式中假定为常数的光纤衰减可能会导致某些实验设置中校准因子的变化。(C)2011年美国医学物理学家协会。[DOI：10.1118/1.3562896]
Purpose: The purposes of this work were: (1) To determine if a spectral method can accurately correct the Cerenkov light effect in plastic scintillation detectors (PSDs) for situations where the Cerenkov light is dominant over the scintillation light and (2) to develop a procedural guideline for accurately determining the calibration factors of PSDs.Methods: The authors demonstrate, by using the equations of the spectral method, that the condition for accurately correcting the effect of Cerenkov light is that the ratio of the two calibration factors must be equal to the ratio of the Cerenkov light measured within the two different spectral regions used for analysis. Based on this proof, the authors propose two new procedures to determine the calibration factors of PSDs, which were designed to respect this condition. A PSD that consists of a cylindrical polystyrene scintillating fiber (1.6 mm(3)) coupled to a plastic optical fiber was calibrated by using these new procedures and the two reference procedures described in the literature. To validate the extracted calibration factors, relative dose profiles and output factors for a 6 MV photon beam from a medical linac were measured with the PSD and an ionization chamber. Emphasis was placed on situations where the Cerenkov light is dominant over the scintillation light and on situations dissimilar to the calibration conditions.Results: The authors found that the accuracy of the spectral method depends on the procedure used to determine the calibration factors of the PSD and on the attenuation properties of the optical fiber used. The results from the relative dose profile measurements showed that the spectral method can correct the Cerenkov light effect with an accuracy level of 1%. The results obtained also indicate that PSDs measure output factors that are lower than those measured with ionization chambers for square field sizes larger than 25 x 25 cm(2), in general agreement with previously published Monte Carlo results.Conclusions: The authors conclude that the spectral method can be used to accurately correct the Cerenkov light effect in PSDs. The authors confirmed the importance of maximizing the difference of Cerenkov light production between calibration measurements. The authors also found that the attenuation of the optical fiber, which is assumed to be constant in the original formulation of the spectral method, may cause a variation of the calibration factors in some experimental setups. (C) 2011 American Association of Physicists in Medicine. [DOI: 10.1118/1.3562896]