Measurement accuracy and Cerenkov removal for high performance, high spatial resolution scintillation dosimetry
Measurement accuracy and Cerenkov removal for high performance, high spatial resolution scintillation dosimetry
复制标题
DOI：
10.1118/1.2138010
复制
发表时间：
2006-01-01
期刊：
影响因子：
3.8
通讯作者：
Beaulieu, L
中科院分区：
文献类型：
--
作者：
Archambault, L;Beddar, AS;Beaulieu, L
随着高度适形放射治疗技术，如调强放射治疗、放射外科和放射治疗在临床实践中变得越来越普遍，这些窄光束的使用在质量保证和剂量测量方面要求更高的精度。塑料闪烁体具有水等效性、能量无关性和剂量率线性等特点，已被证明具有优良的性能，适合最复杂和要求最高的放射治疗计划。塑料闪烁体的主要缺点是在光导中产生切伦科夫辐射，这会导致不想要的茎效应。已经提出了几种技术来最大限度地减少这种影响。在这项研究中，我们比较了三种这样的技术-背景减去、简单过滤和色度去除-在重复性和剂量精度方面，作为它们从剂量信号中消除切伦科夫茎效应的能力的衡量标准。这项研究中使用的剂量计包括一个6毫米(3)塑料闪烁光纤探头，一根光纤，和一个彩色电荷耦合装置相机。整个系统是线性的，在5-S积分时间内，摄像机采集的总光的重复性在0.31%以内。本底减去和色度去除都适合于精确的剂量评估，与电离室的平均绝对剂量偏差分别为0.52%和0.67%。背景减去需要两根光纤，但色度去除只用了一根，从而防止了当强剂量梯度垂直于光纤时可能出现的测量伪影。我们的发现表明，塑料闪烁剂量计可以不受切伦科夫辐射的影响。(C)2006年美国医学物理学家协会。
With highly conformal radiation therapy techniques such as intensity-modulated radiation therapy, radiosurgery, and tomotherapy becoming more common in clinical practice, the use of these narrow beams requires a higher level of precision in quality assurance and dosimetry. Plastic scintillators with their water equivalence, energy independence, and dose rate linearity have been shown to possess excellent qualities that suit the most complex and demanding radiation therapy treatment plans. The primary disadvantage of plastic scintillators is the presence of Cerenkov radiation generated in the light guide, which results in an undesired stem effect. Several techniques have been proposed to minimize this effect. In this study, we compared three such techniques-background subtraction, simple filtering, and chromatic removal-in terms of reproducibility and dose accuracy as gauges of their ability to remove the Cerenkov stem effect from the dose signal. The dosimeter used in this study comprised a 6-mm(3) plastic scintillating fiber probe, an optical fiber, and a color charge-coupled device camera. The whole system was shown to be linear and the total light collected by the camera was reproducible to within 0.31% for 5-s integration time. Background subtraction and chromatic removal were both found to be suitable for precise dose evaluation, with average absolute dose discrepancies of 0.52% and 0.67%, respectively, from ion chamber values. Background subtraction required two optical fibers, but chromatic removal used only one, thereby preventing possible measurement artifacts when a strong dose gradient was perpendicular to the optical fiber. Our findings showed that a plastic scintillation dosimeter could be made free of the effect of Cerenkov radiation. (c) 2006 American Association of Physicists in Medicine.