Calculation of effective dose from measurements of secondary neutron spectra and scattered photon dose from dynamic MLC IMRT for 6 MV, 15 MV, and 18 MV beam energies
Calculation of effective dose from measurements of secondary neutron spectra and scattered photon dose from dynamic MLC IMRT for 6 MV, 15 MV, and 18 MV beam energies
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DOI：
10.1118/1.2140119
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发表时间：
2006-02-01
期刊：
影响因子：
3.8
通讯作者：
Fullerton, GD
中科院分区：
文献类型：
--
作者：
Howell, RM;Hertel, NE;Fullerton, GD
根据6 mV、15 mV和18 mV常规和调强放射治疗(IMRT)前列腺治疗计划计算有效剂量。ICRP-60组织权重因子用于计算。所有光束能量的光子剂量都是以模体为单位测量的。测量了15 mV和18 mV的中子谱以及用于计算环境剂量当量的ICRP-74质量换算因子。使用文献中的中子深度剂量数据对每个组织的环境剂量当量进行了校正。然后用深度校正的中子剂量作为ICRP防护量的中子成分--器官当量剂量的量度。调强放射治疗导致许多器官的光子剂量增加。然而，与常规放射治疗相比，调强放射治疗的有效剂量总体上减少了。这种下降与强度调制场将治疗体积附近的关键正常结构的剂量降至最低的能力有关。在调强放射治疗所用的三种束流能量的比较中，6 mV的有效剂量最低，18 mV的有效剂量最高。这归因于18 mV的中子贡献较大，而6 mV的中子贡献不大。(C)2006年美国医学物理学家协会。
Effective doses were calculated from the delivery of 6 MV, 15 MV, and 18 MV conventional and intensity-modulated radiation therapy (IMRT) prostate treatment plans. ICRP-60 tissue weighting factors were used for the calculations. Photon doses were measured in phantom for all beam energies. Neutron spectra were measured for 15 MV and 18 MV and ICRP-74 quality conversion factors used to calculate ambient dose equivalents. The ambient dose equivalents were corrected for each tissue using neutron depth dose data from the literature. The depth corrected neutron doses were then used as a measure of the neutron component of the ICRP protection quantity, organ equivalent dose. IMRT resulted in an increased photon dose to many organs. However, the IMRT treatments resulted in an overall decrease in effective dose compared to conventional radiotherapy. This decrease correlates to the ability of an intensity-modulated field to minimize dose to critical normal structures in close proximity to the treatment volume. In a comparison of the three beam energies used for the IMRT treatments, 6 MV resulted in the lowest effective dose, while 18 MV resulted in the highest effective dose. This is attributed to the large neutron contribution for 18 MV compared to no neutron contribution for 6 MV. (c) 2006 American Association of Physicists in Medicine.