Institute for National Measurement Standards, National Research Council of Canada, Building M-35, 1200 Montreal Road, Ottawa, Canada.
Med Phys. 2009 Dec;36(12):5586-94. doi: 10.1118/1.3260839.
The objective of this study was to demonstrate that the weight of non-Pb radiation shielding materials can be minimized by structuring the material as a bilayer composed of different metal-powder-embedded elastomer layers.
Measurements and Monte Carlo (MC) calculations were performed to study the attenuation properties of several non-Pb metal bilayers over the x-ray energy range 30-150 keV. Metals for the layers were chosen on the basis of low cost, nontoxicity, and complementary photoelectric absorption characteristics. The EGSnrc user code cavity.cpp was used to calculate the resultant x-ray fluence spectra after attenuation by these metal layers. Air kerma attenuation was measured using commercially manufactured metal/elastomer test layers. These layers were irradiated using the primary standard calibration beams at the Institute for National Measurement Standards in Ottawa, Canada utilizing the six x-ray beam qualities recommended in the German Standard DIN 6857. Both the measurements and the calculations were designed to approximate surface irradiation as well as penetrating radiation at 10 mm depth in soft tissue. The MC modeling point and the position of the measurement detector for surface irradiation were both directly against the downstream face of the attenuating material, as recommended in DIN 6857.
The low-Z upstream/high-Z downstream ordering of the metal bilayers provided substantially more attenuation than the reverse order. Optimal percentages of each metal in each bilayer were determined for each x-ray radiation beam quality.
Depending on the x-ray quality, appropriate choices of two complementary metal-embedded elastomer layers can decrease the weight of radiation shielding garments by up to 25% compared to Pb-based elastomer garments while providing equivalent attenuation.
本研究的目的是证明通过将材料构造成由不同金属粉末嵌入弹性体层组成的双层结构，可以最小化非 Pb 辐射屏蔽材料的重量。
进行了测量和蒙特卡罗（MC）计算，以研究几种非 Pb 金属双层在 30-150keV 的 X 射线能量范围内的衰减特性。选择这些层的金属是基于低成本、无毒和互补光电吸收特性。使用 EGSnrc 用户代码 cavity.cpp 计算这些金属层衰减后的 X 射线荧光光谱。使用商业制造的金属/弹性体测试层测量空气比释动能衰减。这些层在加拿大渥太华国家测量标准研究所利用德国标准 DIN 6857 推荐的六种 X 射线束质量进行辐照。测量和计算都是为了近似表面辐照以及软组织 10mm 深度处的穿透辐射。MC 建模点和表面辐照测量探测器的位置都直接位于衰减材料的下游面，这是 DIN 6857 所建议的。
金属双层的低 Z 上游/高 Z 下游排序提供了比反向排序更多的衰减。为每个 X 射线辐射束质量确定了每个双层中每种金属的最佳百分比。
根据 X 射线质量，适当选择两种互补的金属嵌入弹性体层可以将基于 Pb 的弹性体服装的辐射屏蔽服装重量降低高达 25%，同时提供等效衰减。
