为完成高剂量率192Ir 放射源参考空气比释动能率的绝对测量工作,设计了专用的辐照器及定位装置,利用医用高剂量率近距离治疗机搭建了准直的参考辐射场。参考ISO 4037等相关标准,对参考辐射场的散射、辐射野、半值层、有效能量等相关参数进行了测量和研究。结果显示,在辐射场多个位置,环境散射份额小于主射束的0.003%;在距离放射源1.4m的位置,辐射野直径为98mm,尺寸大于基准石墨空腔电离室;半值层测量结果为8.224mm(Cu),有效能量为402.8keV,利用HPGe探测器测量的192Ir能谱与模拟谱契合度良好。各项参数均满足了192Ir近距离治疗源参考空气比释动能率的量值复现要求,为其绝对测量与国际比对工作打下基础。
Abstract
To complete the absolute measurement of the reference air kerma rate of the high dose rate 192Ir radioactive source, a special irradiator and positioning device was designed, and a collimated reference radiation field was built using a medical high dose rate brachytherapy machine. Concerning relevant standards such as ISO 4037, the scattering, radiation field, half-value layer, effective energy and other related parameters of the reference radiation field were measured. The results show that the ambient scattering share is less than 0.003% of the main beam at multiple locations in the radiation field; at a distance of 1.4 m from the radiation source, the diameter of the radiation field is 98 mm, which is larger than the benchmark graphite cavity ionization chamber; the layer measurement result is Cu of 8.224mm,and the effective energy is 402.8keV. The 192Ir energy spectrum measured by HPGe detector is in good agreement with the simulated spectrum. All the parameters met the requirement of the 192Ir brachytherapy source reference air kerma rate to reproduce the magnitude, which laid the foundation for its absolute measurement and international comparison.
关键词
电离辐射 /
参考空气比释动能率 /
近距离治疗 /
192Ir放射源
Key words
Ionizing radiation /
reference air kerma rate /
brachytherapy /
192Ir radioactive source
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基金
中国计量科学研究院基本科研业务费(AKYZZ2017)
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