Geometrical uncertainties, radiotherapy planning margins, and the ICRU-62 report
Geometrical uncertainties, radiotherapy planning margins, and the ICRU-62 report
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DOI：
10.1016/s0167-8140(02)00140-8
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发表时间：
2002-07-01
影响因子：
5.7
通讯作者：
Heijmen, BJM
中科院分区：
文献类型：
--
作者：
Stroom, JC;Heijmen, BJM
在本文中，我们详细阐述了 ICRU-62 报告中有关放射治疗期间几何不确定性的规划靶区 (PTV) 裕度的建议，例如患者摆位和内部器官运动的变化。根据 ICRU 的规定，这些裕度应确保 PTV 中的计划剂量能够代表“移动”临床目标体积 (CTV) 中的实际剂量。我们证明系统和随机几何不确定性的剂量测定结果是根本不同的，这应该反映在裕度计算中。因此，ICRU-62 报告中的建议通常是无效的，即对系统误差 (Sigma(tot)) 和随机误差 (sigma(tot)) 的标准差进行二次相加来确定裕度计算的总体标准差。相反，之前发布的 PTV 裕度计算公式 M=2Sigma(tot) + 0.7sigma(tot) 确实考虑了系统误差和随机误差对 CTV 剂量的不同影响。如果对于随机和系统不确定性，内部误差和外部误差不相关，并且通过标准差 sigma(int)、sigma(ext)、Sigma(int)、Sigma(ext) 进行量化，则 Sigma(tot) = root(Sigma(int)(2) + Sigma(ext)(2)) 且 sigma(tot) = root(sigma(int)(2) + sigma(ext)(2))。如果故意降低由此获得的 PTV 裕度以保护正常组织，则计划的 PTV 剂量不再代表 CTV。因此，我们建议还报告配方最初定义的体积中的最小剂量（指定的 RTV，即代表性目标体积）。 (C) 2002 Elsevier Science Ireland Ltd. 保留所有权利。
In this paper, we elaborate on the proposals in the ICRU-62 report concerning planning target volume (PTV) margins for geometrical uncertainties during radiotherapy, such as variations in patient set-up and internal organ motion. According to the ICRU, these margins should be such that the planned dose in the PTV is representative of the real dose in the 'moving' clinical target volume (CTV). We demonstrate that the dosimetrical consequences of systematic and random geometrical uncertainties are fundamentally different, which should be reflected in margin calculations. The recommendation in the ICRU-62 report, to quadratically add standard deviations for systematic (Sigma(tot)) and random (sigma(tot)) errors to determine an overall standard deviation for margin calculations, is therefore generally not valid. Instead, a previously published recipe for PTV margin calculation, M=2Sigma(tot) + 0.7sigma(tot), does indeed account for the different impact of systematic and random errors on the dose in the CTV. If, for both random and systematic uncertainties, the internal and external errors are uncorrelated and quantified by the standard deviations sigma(int), sigma(ext), Sigma(int), Sigma(ext), then Sigma(tot) = root(Sigma(int)(2) + Sigma(ext)(2)) and sigma(tot) = root(sigma(int)(2) + sigma(ext)(2)). If the PTV margin thus acquired is deliberately reduced to spare normal tissues, the planned PTV dose is not representative of the CTV anymore. Therefore, we recommend to also report the minimum dose in the volume originally defined by the recipe (designated RTV, i.e. representative target volume). (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.