Statistical simulations to estimate motion-inclusive dose-volume histograms for prediction of rectal morbidity following radiotherapy.
Statistical simulations to estimate motion-inclusive dose-volume histograms for prediction of rectal morbidity following radiotherapy.
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DOI：
10.3109/0284186x.2012.720382
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发表时间：
2013-04
期刊：
影响因子：
--
通讯作者：
Muren LP
中科院分区：
文献类型：
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作者：
Thor M;Apte A;Deasy JO;Muren LP
放射治疗(RT)过程中的内部器官运动会导致实际给药剂量分布的不确定性。在预测RT发病率的研究中，治疗计划计算机断层扫描(PCT)提供的单次剂量估计通常被假定为代表整个RT过程中的剂量分布。本文介绍了一个描述器官运动的简单模型，并将其与晚期直肠发病率数据相关联，目的是为了提高发病率预测。器官运动由正态分布的平移运动描述，其大小由该分布的标准差(SD)表征。模拟了各向同性和各向异性(仅前-后)运动模式，以及随机、系统或组合的随机和系统运动。用Spearman等级相关系数(Rs)对232例前列腺癌患者的晚期直肠发病率与运动-包括剂量-体积直方图(DDVH)之间的关系进行了量化，并与静态/计划DVH(PDVH)进行了比较。对于各向同性和各向异性运动，dDVH相对于pDVH与直肠发病率的相关性不同。在中剂量区(40-60Gy区)差异最为明显。这些关联依赖于应用的运动模式，与应用SD在0.2-0.8厘米范围内的随机运动获得的发病率的相关性最强。在这项研究中，我们介绍了一个简单的模型来描述在RT过程中发生的器官运动。与计划剂量分布的相关性相比，运动包含性剂量分布与直肠发病率之间存在不同的剂量-体积依赖关系，并且在某些情况下，剂量-体积相关性更强。这表明，RT期间直肠器官的运动影响了仅使用计划分布来模拟发病率风险的努力。
Internal organ motion over a course of radiotherapy (RT) leads to uncertainties in the actual delivered dose distributions. In studies predicting RT morbidity, the single estimate of the delivered dose provided by the treatment planning computed tomography (pCT) is typically assumed to be representative of the dose distribution throughout the course of RT. In this paper, a simple model for describing organ motion is introduced, and is associated to late rectal morbidity data, with the aim of improving morbidity prediction. Organ motion was described by normally distributed translational motion, with its magnitude characterised by the standard deviation (SD) of this distribution. Simulations of both isotropic and anisotropic (anterior-posterior only) motion patterns were performed, as were random, systematic or combined random and systematic motion. The associations between late rectal morbidity and motion-inclusive delivered dose-volume histograms (dDVHs) were quantified using Spearman's rank correlation coefficient (Rs) in a series of 232 prostate cancer patients, and were compared to the associations obtained with the static/planned DVH (pDVH). For both isotropic and anisotropic motion, different associations with rectal morbidity were seen with the dDVHs relative to the pDVHs. The differences were most pronounced in the mid-dose region (40–60 Gy). The associations were dependent on the applied motion patterns, with the strongest association with morbidity obtained by applying random motion with an SD in the range 0.2–0.8 cm. In this study we have introduced a simple model for describing organ motion occurring during RT. Differing and, for some cases, stronger dose-volume dependencies were found between the motion-inclusive dose distributions and rectal morbidity as compared to the associations with the planned dose distributions. This indicates that rectal organ motion during RT influences the efforts to model the risk of morbidity using planning distributions alone.