The effect of set-up uncertainties, contour changes, and tissue inhomogeneities on target dose-volume histograms
The effect of set-up uncertainties, contour changes, and tissue inhomogeneities on target dose-volume histograms
复制标题
设置不确定性、轮廓变化和组织不均匀性对靶剂量-体积直方图的影响
DOI：
10.1118/1.1508800
复制
发表时间：
2002-10-01
期刊：
影响因子：
3.8
通讯作者：
Bartelink, H
中科院分区：
文献类型：
--
作者：
Cho, BCJ;van Herk, M;Bartelink, H
了解设置不确定性对剂量分布的影响是一个重要的临床问题，但由于它们依赖于组织的不均匀性和表面轮廓的变化(即变化效应)，因此很难准确建模。其目的是：(1)评估和量化设置不确定性、轮廓变化和组织不均匀对靶区剂量-体积直方图(DVH)的不变和变异影响；(2)提出一种内插(变异)DVH的方法。我们提出了一个肺癌患者来评估目标DVH的设置不确定性、轮廓变化和组织不均质性的重要性。对于15个位移误差(相对于等中心)，使用(1)等中心处剂量分布的不变移位，(2)全变计算，以及(3)应用于稀疏采样的可变DVH的B-样条插值法来计算微分DVH。所有剂量计算均采用折叠圆锥体算法。剂量学差异用均方根(RMS)偏差和等效均匀剂量(EUD)来量化。为了确定安装不确定性的影响，采用了加权平均EUD，假设位移误差为正态分布。积分DVHs相对剂量的最大绝对差值和均方根偏差分别为65.2%和5.8%和16.9%和2.5%。同样，最大绝对差值和均方根偏差作为设置不确定度之间的函数：(1)不变曲线和计算曲线之间的标准差为0.02GY和0.01GY；(2)内插曲线和计算曲线之间的不确定度标准差为0.01GY和0.006 GY。由于选择了一个“最坏情况”的例子，我们得出的结论是，在大多数临床病例中，轮廓变化、组织不均质性和设置的不确定性对EUD的不同影响可以忽略不计。插值法是逼近DVH的一种有效、高效的方法。(C)2002年美国医学物理学家协会。
Understanding set-up uncertainty effects on dose distributions is an important clinical problem but difficult to model accurately due to their dependence on tissue inhomogeneities and changes in the surface contour (i.e., variant effects). The aims are: (1) to evaluate and quantify the invariant and variant effects of set-up uncertainties, contour changes and tissue inhomogeneities on target dose-volume histograms (DVHs); (2) to propose a method to interpolate (variant) DVHs. We present a lung cancer patient to estimate the significance of set-up uncertainties, contour changes and tissue inhomogeneities in target DVHs. Differential DVHs are calculated for 15 displacement errors (with respect to the isocenter) using (1) an invariant shift of the dose distribution at the isocenter, (2) a full variant calculation, and (3) a B-spline interpolation applied to sparsely sampled variant DVHs. The collapsed cone algorithm was used for all dose calculations. Dosimetric differences are quantified with the root mean square (RMS) deviation and the equivalent uniform dose (EUD). To determine set-up uncertainty effects, weighted mean EUDs, assuming normally distributed displacement errors, are used. The maximum absolute difference and RMS deviation in the integral DVHs' relative dose between (1) the invariant and calculated curves are 65.2% and 5.8% and (2) the interpolated and calculated curves are 16.9% and 2.5%. Similarly, the maximum absolute difference and RMS deviation in mean EUD as a function of the set-up uncertainty's standard deviation between (1) the invariant and calculated curves are 0.02 and 0.01 Gy; and (2) the interpolated and calculated curves are 0.01 and 0.006 Gy. Since a "worst-case" example is selected, we conclude that, in the majority of clinical cases, the variant effects of contour changes, tissue inhomogeneities and set-up uncertainties on EUD are negligible. Interpolation is a valid, efficient method to approximate DVHs. (C) 2002 American Association of Physicists in Medicine.