Saidi Pooneh, Sadeghi Mahdi, Shirazi Alireza, Tenreiro Claudio
Department of Nuclear Engineering, Research and Science Branch, Islamic Azad University, Tehran, Iran.
Australas Phys Eng Sci Med. 2011 Jun;34(2):223-31. doi: 10.1007/s13246-011-0069-1. Epub 2011 Mar 31.
Brachytherapy dose distributions are calculated for 15 mm ROPES eye plaque loaded with model Theragenics200 and IR06-(103)Pd seeds. The effects of stainless steel backing and Acrylic insert on dose distribution along the central axis of the eye plaque and at critical ocular structure are investigated. Monte Carlo simulation was carried out with the Version 5 of the MCNP. The dose at critical ocular structure by considering the eye composition was calculated. Results are compared with the calculated data for COMS eye plaque loaded with Theragenics200 palladium-103 seeds and model 6711 iodine-125 seed. The air kerma strength of the IR06-(103)Pd seed to deliver 85 Gy in apex of tumor in water medium was calculated to be 4.10 U/seed. Along the central axis of stainless steel plaque loaded with new (103)Pd seeds in Acrylic insert, the dose reduction relative to water is 6.9% at 5 mm (apex). Removal of the Acrylic insert from the plaque (replacing with water) did not make significantly difference in dose reduction results (~0.2%). The presence of the stainless steel backing results in dose enhancement near the plaque relative to water. Doses at points of interest are higher for ROPES eye plaque when compared to COMS eye plaque. The dosimetric parameters calculated in this work for the new palladium seed, showed that in dosimetry point of view, the IR06-(103)Pd seed is suitable for use in brachytherapy. The effect of Acrylic insert on dose distribution is negligible and the main effect on dose reduction is due to the presence of stainless steel plaque backing.
针对装载了Theragenics200和IR06-(103)Pd种子模型的15毫米ROPES眼模，计算近距离放射治疗剂量分布。研究了不锈钢背板和丙烯酸插入物对眼模中心轴沿线及关键眼部结构处剂量分布的影响。使用MCNP第5版进行蒙特卡罗模拟。考虑眼部组成，计算关键眼部结构处的剂量。将结果与装载Theragenics200钯-103种子和6711碘-125种子模型的COMS眼模的计算数据进行比较。计算得出，在水介质中肿瘤顶端给予85 Gy剂量时，IR06-(103)Pd种子的空气比释动能强度为4.10 U/种子。在装载于丙烯酸插入物中的新型(103)Pd种子的不锈钢眼模中心轴上，在5毫米（顶端）处相对于水的剂量降低为6.9%。从眼模中移除丙烯酸插入物（用水替代）在剂量降低结果方面没有显著差异（约0.2%）。不锈钢背板的存在导致眼模附近相对于水的剂量增强。与COMS眼模相比，ROPES眼模在感兴趣点处的剂量更高。这项工作中针对新型钯种子计算的剂量学参数表明，从剂量学角度来看，IR06-(103)Pd种子适用于近距离放射治疗。丙烯酸插入物对剂量分布的影响可忽略不计，剂量降低的主要影响因素是不锈钢眼模背板的存在。
