Pacific Northwest National Laboratory, Richland, Washington 99354.
Mount Sinai Hospital, New York, New York 10029.
Radiat Res. 2019 Nov;192(5):493-506. doi: 10.1667/RR15395.1. Epub 2019 Sep 10.
Irradiators utilizing radioactive cesium-137 (Cs) or cobalt-60 (Co) gamma-ray sources have been used for biological applications for many decades. These applications include irradiation of much of the nation's blood supply and radiation biology research. In 2005, the U.S. Nuclear Regulatory Commission was assigned the task of preventing the misuse of radioactive materials by persons with malicious intentions; gamma-ray sources, in particular, were given high priority. This resulted in increased security requirements, including constant surveillance, controlled access and personnel background checks. As a result of such regulations being introduced, organizations considering the purchase of a gamma-ray irradiator for the first time or as a replacement to an existing one due to radioactive decay, are now looking into alternative technologies, primarily an X-ray irradiator. To make an educated decision on whether a particular type of X-ray irradiator is of sufficient equivalency to a particular type of Cs irradiator for specific applications, one must rely on relevant published comparison studies from other researchers, or perform the comparison studies on their own. This work focuses on the comparison of the radiation physics aspects of two Cs irradiator models and three X-ray irradiator models, for the purpose of determining whether the X-ray irradiator models could validly replace the Cs irradiator models for certain applications. Although evaluating the influence of relative biological effectiveness (RBE) differences among irradiators could be part of this study, that has been left for a related publication focused on the theoretical aspects of this topic. These evaluations were performed utilizing 47-g and 120-g tissue-equivalent rodent dosimetry phantoms. Our results indicate that, depending upon the user's dose uncertainty budget and maximum areal density of specimens to be irradiated, the RS 2000 160 kVp X-ray irradiator, X-RAD160 X-ray irradiator or X-RAD320 X-ray irradiator could successfully replace a Cs irradiator. Technically, any X-ray irradiator model providing similar irradiation geometry, and average energy similar to or higher than these three X-ray models, could also successfully replace a Cs irradiator. The results also reveal that differences in inherent source geometry, field geometry and irradiation geometry can counter some of the influence due to differences in energy spectrum. Our goal is that this publication be used as a guide for other similar studies, providing investigators with information on important details that can make the difference between strong and weak comparison conclusions.
几十年来，利用放射性铯-137（Cs）或钴-60（Co）伽马射线源的辐照器一直用于生物应用。这些应用包括辐照全国大部分的血液供应和辐射生物学研究。2005 年，美国核管理委员会（NRC）被赋予防止怀有恶意的人滥用放射性材料的任务；伽马射线源，特别是钴-60 伽马射线源，被给予高度优先考虑。这导致了更高的安全要求，包括持续监控、受控访问和人员背景检查。由于引入了这些规定，那些首次考虑购买伽马射线辐照器或由于放射性衰变而更换现有辐照器的组织，现在正在研究替代技术，主要是 X 射线辐照器。为了在特定应用中对特定类型的 X 射线辐照器是否与特定类型的 Cs 辐照器具有足够的等效性做出明智的决策，必须依赖其他研究人员的相关已发表的比较研究，或者自行进行比较研究。这项工作重点比较了两种 Cs 辐照器模型和三种 X 射线辐照器模型的辐射物理方面，目的是确定 X 射线辐照器模型是否可以有效地替代某些应用中的 Cs 辐照器模型。尽管评估辐照器之间相对生物效应（RBE）差异的影响可能是本研究的一部分，但这已留作一篇专注于该主题理论方面的相关出版物。这些评估是利用 47-g 和 120-g 组织等效啮齿动物剂量体模进行的。我们的结果表明，根据用户的剂量不确定度预算和要辐照的最大面密度标本，RS 2000 160 kVp X 射线辐照器、X-RAD160 X 射线辐照器或 X-RAD320 X 射线辐照器可以成功替代 Cs 辐照器。从技术上讲，任何提供类似辐照几何形状的 X 射线辐照器模型，以及平均能量与这三种 X 射线模型相似或更高的模型，也可以成功替代 Cs 辐照器。结果还表明，固有源几何形状、场几何形状和辐照几何形状的差异可以抵消由于能谱差异而产生的一些影响。我们的目标是，本出版物可用作其他类似研究的指南，为研究人员提供重要细节信息，这些信息可以使对比结论强弱产生差异。
