在放射生物学研究中使用 X 射线机的辐射场和剂量不均匀性。

Radiation field and dose inhomogeneities using an X-ray cabinet in radiation biology research.

机构信息

Department of Effects and Risks of Ionising and Non-Ionising Radiation, Federal Office for Radiation Protection, Oberschleissheim, Germany.

Department of Medical and Occupational Radiation Protection, Federal Office for Radiation Protection, Oberschleissheim, Germany.

出版信息

Med Phys. 2021 Dec;48(12):8140-8151. doi: 10.1002/mp.15297. Epub 2021 Oct 29.

DOI:10.1002/mp.15297

PMID:34655237

Abstract

PURPOSE

X-ray cabinets are replacing Cs/ Co sources in radiation biology research due to advantages in size, handling, and radiation protection. However, because of their different physical properties, X-ray cabinets are more susceptible to experimental influences than conventional sources. The aim of this study was to examine the variations related to the experimental setups typically used to investigate biological radiation effects with X-ray cabinets.

MATERIALS AND METHODS

A combined approach of physical dose measurements by thermoluminescence dosimetry and detection of biological effects by quantification of γH2AX and 53BP1 foci was used to analyze field inhomogeneity and evaluate the influence of the components of the experimental setup.

RESULTS

Irradiation was performed using an X-ray tube (195 kV, 10 mA, 0.5-mm-thick copper filter, dose rate of 0.59 Gy/min). Thermoluminescence dosimetry revealed inhomogeneity and a dose decrease of up to 42.3% within the beam area (diameter 31.1 cm) compared to the dose at the center. This dose decrease was consistent with the observed decline in the number of radiation-induced foci by up to 55.9 %. Uniform dose distribution was measured after reducing the size of the radiation field (diameter 12.5 cm). However, when using 15-ml test tubes placed at different positions within this field, the dose decreased by up to 17% in comparison to the central position. Analysis of foci number revealed significant differences between the tubes for γH2AX (1 h) and 53BP1 (4 h) at different time points after irradiation. Neither removal of some tubes nor of the caps improved the dose decrease significantly. By contrast, when using 1.5-ml tubes, dose differences were less than 4%, and no significant differences in foci number were detected.

CONCLUSION

X-ray cabinets are user-friendly irradiation units for investigating biological radiation effects. However, field inhomogeneities and experimental setup components considerably affect the delivered irradiation doses. For this reason, strict dosimetric monitoring of experimental irradiation setups is mandatory for reliable studies.

摘要

目的

由于尺寸、处理和辐射防护方面的优势，X 射线机正在取代 Cs/Co 源，用于辐射生物学研究。然而，由于其物理性质不同，X 射线机比传统源更容易受到实验影响。本研究旨在检查与通常用于研究 X 射线机生物辐射效应的实验设置相关的变化。

材料与方法

采用热释光剂量测量的物理剂量测量和γH2AX 和 53BP1 焦点数量的生物效应检测相结合的方法，分析场不均匀性并评估实验设置组件的影响。

结果

使用 X 射线管（195kV、10mA、0.5mm 厚铜滤器、剂量率为 0.59Gy/min）进行照射。热释光剂量测量显示，与中心剂量相比，在光束区域（直径 31.1cm）内存在不均匀性和剂量降低，最大可达 42.3%。观察到的辐射诱导焦点数量减少最多可达 55.9%，与剂量降低一致。当减小辐射场的尺寸（直径 12.5cm）时，测量到均匀的剂量分布。然而，当将 15ml 测试管放置在该场的不同位置时，与中心位置相比，剂量降低最多可达 17%。照射后不同时间点的 γH2AX（1h）和 53BP1（4h）焦点数量分析显示，不同管之间存在显著差异。去除一些管或管帽并不能显著改善剂量降低。相比之下，当使用 1.5ml 管时，剂量差异小于 4%，并且未检测到焦点数量的显著差异。