Estimation of radiation shielding ability in electron therapy and brachytherapy with real time variable shape tungsten rubber
Estimation of radiation shielding ability in electron therapy and brachytherapy with real time variable shape tungsten rubber
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DOI：
10.1016/j.ejmp.2019.09.233
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发表时间：
2019-10-01
影响因子：
3.4
通讯作者：
Nishimura, Yasumasa
中科院分区：
文献类型：
--
作者：
Monzen, Hajime;Tamura, Mikoto;Nishimura, Yasumasa
目的：阐明新型实时变形状含钨橡胶(STR)的热变化特性，评价其对Ir-192辐射的屏蔽能力。方法：在-60℃~60℃的温度范围内，对密度为7.3g/cm(3)的STR进行了频率为1.0 Hz的动态力学分析，并评价了其损耗系数(E‘’/E‘)。测量了6 MeV和12 MeV电子束的透射率，并与低熔点合金(LMA)的深度剂量百分比和横向剂量分布进行了比较。对于Ir-192对伽马射线的屏蔽率，获得了测量数据和蒙特卡罗模拟数据，STR厚度从1 mm到16.0 mm。结果：在36℃时，tan delta值为0.520，在60℃时，此值为1.016。对于6 MeV和12 MeV电子束，透射率随着STR厚度的增加而降低，当STR厚度分别为>；7.0和>；12.0 mm时，透过率分别达到约1.0%和4.0%的平台值。剂量分布与LMA的剂量分布基本相同。对于伽马射线，对Ir-192获得50%衰减率的短程辐射厚度为5.804毫米。蒙特卡罗计算结果比实测值平均高出2.6%。结论：STR可在60℃下实时改变形状，并在体温下保持其形状。它具有足够的屏蔽能力，可以抵御来自Ir-192的兆伏电子束和伽马射线。
Purpose: To clarify the physical characteristics of a newly developed real time variable shape rubber containing tungsten (STR) with changes in heat and estimate its shielding abilities against electron beams and gamma-rays from Ir-192.Methods: Dynamic mechanical analysis for the STR (density = 7.3 g/cm(3)) was conducted at a frequency of 1.0 Hz in the temperature range of -60 degrees C to 60 degrees C. We evaluated tan delta, defined as the ratio (E ''/E') between the storage modulus (E') and loss modulus (E ''). The transmission rates were measured against 6- and 12-MeV electron beams and the percentage depth dose and lateral dose profile were compared with low-melting alloy (LMA). For the shielding rate of Ir-192 against gamma-rays, measurement data and Monte Carlo simulation data were obtained with STR thickness ranging from 1.0 mm to 16.0 mm.Results: At 36 degrees C, the tan delta value was 0.520, while at 60 degrees C, this value was 1.016. For 6- and 12-MeV electron beams, the transmission rates decreased with increasing STR thickness and reached plateaus at approximately 1.0% and 4.0% with STR thickness of > 7.0 and > 12.0 mm, respectively. The dose distributions were almost equal to those for LMA. Against gamma-rays, the thickness of STR that obtained a 50% attenuation rate for Ir-192 was 5.804 mm. The Monte Carlo calculation results were 2.6% higher on average than the measurement results.Conclusion: The STR can be changed shape in real time at 60 degrees C and maintains its shape at body temperatures. It has adequate shielding abilities against megavoltage electron beams and gamma-rays from Ir-192.