施源器材料对192Ir后装源水中吸收剂量的影响

目的 应用3D打印支架联合人造金刚石探头测量施源器材料对高剂量率后装¹⁹²Ir源水中吸收剂量的影响。方法 将金刚石探头与塑料插植针分别固定在3D打印支架上，金刚石探头的中心轴与塑料插植针的中心轴在一个平面内相互垂直。采用模拟源尺测量实测驻留位置为248 mm，该驻留位置与逐点测量的最大响应位置吻合。测量材料有304不锈钢、聚亚苯基砜树脂（PPSU）材料、有机玻璃（PMMA）材料和3D打印聚乳酸（PLA）材质。测量水中不同厚度或不同填充率的材料对吸收剂量的衰减。结果 304不锈钢和PPSU材料厚度与相对剂量的线性拟合公式分别为y=-0.029 7x+1.000 3，y=-0.002 3x+1.010 2；拟合优度R²分别为0.925 3和0.722 2。10 mm以内PMMA材料对剂量的影响均<1.5%。3D打印材料填充率（%）与相对剂量的线性拟合公式为y=-0.000 4x+1.024 6，拟合优度R²为0.854 5。结论 施源器材料，尤其是高密度材料（如304不锈钢）和新型技术材料（如3D打印PLA），对¹⁹²Ir后装源的吸收剂量影响需引起施源器开发人员和临床应用者的足够重视。

Effect of applicator materials on absorbed dose in water from afterloading 92Ir source

Objective To measure the effect of applicator materials on absorbed dose in water from HDR afterloading ¹⁹²Ir source by using three-dimensional printed holder (3DPH) and synthetic single-crystal diamond detector (SSCDD ). Methods SSCDD and plastic implants were fixed on the 3DPH in turn. The central axis of SSCDD was perpendicular to that of plastic implant needle on the same plane. The actual residence dwell position measured using source position simulator was 248 mm, which was consistent with the maximum response dwell position measured in a point by point way. The materials for measurement included 304 stainless steel, polyphenylene sulfone resins (PPSU), polymethyl methacrylate (PMMA) and 3-D printed polylactic acid (PLA), respectively. The attenuation of absorbed dose in water with different thickness or filling ratio was measured. Results The linear fitting formula of relative dose varying with thickness (mm) for 304 stainless steel and PPSU materials were y=-0.029 7x+ 1.000 3 and y=-0.002 3x +1.010 2, respectively. And the goodness-of-fits were 0.925 3 and 0.722 2, respectively. The effect on dose of PMMA materials within 10 mm was less than 1%. The linear fitting formula of relative dose varying with filling ratio (%) for PLA materials with 10 mm thickness was y=-0.000 4x+1.024 6, with a goodness-of-fit of 0.854 5. Conclusions The effect of applicator materials on the absorbed dose arising from afterloading ¹⁹²Ir source should attract enough attention of both developers and clinical users, especially with regard to high-density materials like 304 stainless steel and new technology materials such as 3D printed polylactic acid.