Farahani M, Eichmiller F C, McLaughlin W L
ADAHF Paffenbarger Research Center, National Institute of Standards and Technology, Gaithersburg, Maryland 20899.
Med Phys. 1993 Jul-Aug;20(4):1237-41. doi: 10.1118/1.597152.
Shields and stents of metals with high atomic number, which are custom cast in molds from the melt, are the materials most widely used to protect surrounding tissues during treatment of skin or oral lesions with therapeutic electron beams. An improved fabrication method is to mix a polysiloxane-metal composite, which is readily cast at room temperature by combining a metal-powder/polysiloxane resin mixture with a hardening catalyst. The purpose of the present study is to compare the shielding effectiveness of two different metal-polysiloxane composites with that of conventional cast Lipowitz metal (50.1% Bi, 26.6% Pb, 13.3% Sn, 10% Cd). Also, a 2(3) factorial experiment was run to investigate the effects and interactions of metal particle size (20-microns vs 100-microns diameter), the atomic weight of the metal (304 stainless steel vs 70% Ag, 30% Cu alloy), and the presence or absence of a layer of unfilled polymer added to the forward-scatter side of the shield. The composites of different thicknesses were made by blending 90% (w/w) metal powder separately with 10% polysiloxane base and catalyst. A thin GafChromic dosimeter film was placed between the shielding material and a polystyrene base to measure the radiation shielding effect of composite disc samples irradiated with a 6-MeV electron beam normal to the flat surface of the disc. The results show that composite shields with the metal of higher atomic weight and density (Ag-Cu) combined with an additional unfilled layer are more effective than the stainless-steel composite with a similar additional unfilled layer, in terms of diminishing the dose at the surface of the polystyrene backing material.(ABSTRACT TRUNCATED AT 250 WORDS)
高原子序数金属制成的屏蔽物和支架是在模具中由熔体定制铸造而成的，它们是在用治疗性电子束治疗皮肤或口腔病变时最广泛用于保护周围组织的材料。一种改进的制造方法是混合聚硅氧烷 - 金属复合材料，通过将金属粉末/聚硅氧烷树脂混合物与硬化催化剂结合，这种复合材料在室温下易于铸造。本研究的目的是比较两种不同的金属 - 聚硅氧烷复合材料与传统铸造的利波维茨金属（50.1%铋、26.6%铅、13.3%锡、10%镉）的屏蔽效果。此外，还进行了一项2(3)析因实验，以研究金属颗粒大小（直径20微米与100微米）、金属的原子量（304不锈钢与70%银、30%铜合金）以及在屏蔽物的前向散射侧添加或不添加一层未填充聚合物的影响和相互作用。不同厚度的复合材料是通过将90%（重量/重量）的金属粉末分别与10%的聚硅氧烷基料和催化剂混合制成的。在屏蔽材料和聚苯乙烯基底之间放置一片薄的GafChromic剂量计薄膜，以测量用垂直于圆盘平面的6兆电子伏电子束照射的复合圆盘样品的辐射屏蔽效果。结果表明，就减少聚苯乙烯背衬材料表面的剂量而言，具有较高原子量和密度的金属（银 - 铜）与额外未填充层相结合的复合屏蔽物比具有类似额外未填充层的不锈钢复合材料更有效。（摘要截断于250字）
