Dose-wall histograms and normalized dose-surface histograms for the rectum: A new method to analyze the dose distribution over the rectum in conformal radiotherapy
Dose-wall histograms and normalized dose-surface histograms for the rectum: A new method to analyze the dose distribution over the rectum in conformal radiotherapy
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DOI：
10.1016/s0360-3016(99)00270-9
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发表时间：
1999-11-01
影响因子：
7
通讯作者：
Lebesque, JV
中科院分区：
文献类型：
--
作者：
Meijer, GJ;Van den Brink, M;Lebesque, JV
目的：开发一种仅基于直肠壁外轮廓生成直肠壁剂量 - 体积直方图（DVH）的精确方法。
方法和材料：建立了一个直肠壁的数学模型，该模型考虑了由于直肠充盈程度不同以及邻近结构导致的直肠壁拉伸。该模型基于这样一个假设：垂直于直肠中心轴的相交直肠壁组织量是恒定的。该模型的主要目的是确定每个壁单元中直肠壁的厚度。描述了两种方法，每种方法都仅基于所描绘的直肠外轮廓生成直肠壁的DVH。在第一种方法中，利用该模型从轴向外轮廓创建一组内轮廓。这两组轮廓都用于推导直肠的剂量 - 壁直方图（DWH）。在第二种方法中，利用该模型生成一个标准化的二维采样空间，随后将其划分到一个标准化剂量 - 表面直方图（NDSH）中。使用20组CT数据（5名患者×4次扫描）对该模型进行了验证，在这些数据中仔细描绘了直肠的内外轮廓。将DWH和NDSH与需要描绘直肠壁内外表面的直肠壁DVH以及整个直肠（包括直肠充盈部分）的DVH进行了比较。使用正常组织并发症概率（NTCP）计算研究了DWH、NDSH和DVH之间的差异。
结果：CT数据上所描绘的直肠局部壁厚度与所描述的直肠模型相符。每单位长度直肠的直肠壁组织量在患者之间差异很大（27%，1标准差）。在所有分析的患者中，DWH和NDSH与直肠壁的DVH吻合良好。在整个直肠的DVH和直肠壁的DVH之间观察到更多的差异。
结论：所应用的方法可得出直肠壁的准确剂量分布，而无需描绘直肠内表面。这既减少了工作量，又减少了由于直肠壁描绘不准确而导致的差异。DWH和NDSH是评估直肠壁三维剂量分布以及估计高剂量适形放疗中直肠并发症概率的有效工具。（C）1999年爱思唯尔科学公司
Purpose: To develop an accurate method to generate a dose-volume histogram (DVH) of the rectum wall, solely based on the outer contours of the rectum wan.Methods and Materials: A mathematical model for the rectum wall is developed, incorporating the stretching of the rectum wall due to variable rectal filling and neighboring structures. The model is based on the assumption that the amount of intersected rectum wall tissue normal to the central axis of the rectum is constant. The main objective of the model is to determine the thickness of the rectum wall in each wall element. Two approaches are described, each yielding a DVH of the rectum wall, based only on the delineated outer contours of the rectum. In the first approach, the model is used to create a set of inner contours out of the axial outer contours. Both sets of contours are used to derive a dose-wall histogram (DWH) of the rectum. In the second approach, the model is used to generate a normalized 2D sampling space, which is subsequently binned into a normalized dose-surface histogram (NDSH). The model is verified using 20 sets of CT data (5 patients x 4 scans) in which both outer and inner contours of the rectum are carefully delineated. The DWHs and NDSHs are compared with DVHs of the rectum wall, which require contouring of the outer and inner surfaces of the rectum wall, and with DVHs of the total rectum (including rectal filling). The variation between DWHs, NDSHs, and DVHs is investigated using normal tissue complication probability (NTCP) calculations.Results: The local wall thickness of the rectum as outlined on CT data was in conformity with the described rectum model. The amount of rectum wall tissue per unit length rectum varied considerably between patients (27%, 1 SD). In all analyzed patients, the DWHs and NDSHs corresponded well to the DVHs of the rectum wall. Much more discrepancies were observed between the DVHs of the total rectum and the DVHs of the rectum wall.Conclusion: The applied methods yield accurate dose distributions of the rectum wall, without delineating the inner surface of the rectum. This reduces both the workload and variations due to inaccurate delineation of the rectum wall. The DWH and NDSH are effective tools to evaluate 3D dose distributions of the rectum wall and to estimate the complication probability of the rectum in high-dose conformal radiotherapy. (C) 1999 Elsevier Science Inc.