Vishwakarma Ramkrushna S, Selvam T Palani, Sahoo Sridhar, Mishra Subhalaxmi, Chourasiya Ghanshyam
Radiological Physics and Advisory Division, Health, Safety and Environment Group, Bhabha Atomic Research Centre, Anushaktinagar, Mumbai, Maharastra, India.
J Med Phys. 2013 Oct;38(4):158-64. doi: 10.4103/0971-6203.121192.
Investigation of solid phantom materials such as solid water, virtual water, plastic water, RW1, polystyrene, and polymethylmethacrylate (PMMA) for their equivalence to liquid water at (137)Cs energy (photon energy of 662 keV) under full scatter conditions is carried out using the EGSnrc Monte Carlo code system. Monte Carlo-based EGSnrc code system was used in the work to calculate distance-dependent phantom scatter corrections. The study also includes separation of primary and scattered dose components. Monte Carlo simulations are carried out using primary particle histories up to 5 × 10(9) to attain less than 0.3% statistical uncertainties in the estimation of dose. Water equivalence of various solid phantoms such as solid water, virtual water, RW1, PMMA, polystyrene, and plastic water materials are investigated at (137)Cs energy under full scatter conditions. The investigation reveals that solid water, virtual water, and RW1 phantoms are water equivalent up to 15 cm from the source. Phantom materials such as plastic water, PMMA, and polystyrene phantom materials are water equivalent up to 10 cm. At 15 cm from the source, the phantom scatter corrections are 1.035, 1.050, and 0.949 for the phantoms PMMA, plastic water, and polystyrene, respectively.
使用EGSnrc蒙特卡罗代码系统，对固态水、虚拟水、塑料水、RW1、聚苯乙烯和聚甲基丙烯酸甲酯（PMMA）等固态体模材料在（137）Cs能量（光子能量为662 keV）下全散射条件下与液态水的等效性进行了研究。工作中使用基于蒙特卡罗的EGSnrc代码系统来计算与距离相关的体模散射校正。该研究还包括分离原发射线剂量分量和散射剂量分量。进行蒙特卡罗模拟时使用的原粒子历史数高达5×10⁹，以在剂量估计中获得小于0.3%的统计不确定度。在全散射条件下，对（137）Cs能量下各种固态体模（如固态水、虚拟水、RW1、PMMA、聚苯乙烯和塑料水材料）的水等效性进行了研究。研究表明，固态水、虚拟水和RW1体模在距源15 cm范围内是水等效的。塑料水、PMMA和聚苯乙烯体模材料等体模材料在距源10 cm范围内是水等效的。在距源15 cm处，PMMA、塑料水和聚苯乙烯体模的体模散射校正分别为1.035、1.050和0.949。
