How extensive of a 4D dataset is needed to estimate cumulative dose distribution plan evaluation metrics in conformal lung therapy?
How extensive of a 4D dataset is needed to estimate cumulative dose distribution plan evaluation metrics in conformal lung therapy?
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DOI：
10.1118/1.2400624
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发表时间：
2007-01-01
期刊：
影响因子：
3.8
通讯作者：
Ten Haken, Randall K.
中科院分区：
文献类型：
--
作者：
Rosu, Mihaela;Balter, James M.;Ten Haken, Randall K.
本研究的目的是研究使用6 MV光子靶向肿瘤的四维（4D）适形放射治疗中，充分接近胸部解剖结构变形/移动的临床相关累积剂量所需的中间状态数量。4名患者参与了这项研究。对于前三名患者，在呼气和吸气时获得的计算机断层扫描图像是可用的;它们使用B样条变形模型进行配准，并进一步使用计算机变换来模拟呼气和吸气之间的中间状态。对于第4例患者，4D采集的相位排序数据集可用，每个数据集均与呼气数据集配准。呼气-吸气变换也用于模拟中间状态，以比较使用实际数据集和模拟数据集计算的累积剂量。使用剂量计划方法（Dose Planning Method，简称DPL）蒙特卡罗代码计算每个状态的剂量，并通过每个状态的转换矩阵和时间加权因子累积剂量，用于对呼气解剖结构进行评分。使用越来越多的中间状态估计累积剂量，并与更简单的情况进行比较，如“2-状态”模型，该模型仅使用呼气和吸气数据集或呼吸周期平均阶段期间接受的剂量。使用剂量体积直方图和几个治疗评价指标（例如平均肺剂量、正常组织并发症概率和广义均匀剂量）评估每个建模状态的剂量分布以及累积剂量。尽管在每个呼吸状态之间可以存在显著的“点剂量”差异，但是当考虑累积剂量时，差异减小，并且在取决于临床终点的评估度量方面可以变得不太显著。这项研究表明，对于肺癌的某些重要的“临床”终点，可以通过计算呼吸周期的几个阶段（甚至简单地说是平均阶段）的剂量来实现对扭曲解剖结构所接收的累积总剂量的满意预测。(c)2007年美国医学物理学家协会。
The purpose of this study was to investigate the number of intermediate states required to adequately approximate the clinically relevant cumulative dose to deforming/moving thoracic anatomy in four-dimensional (4D) conformal radiotherapy that uses 6 MV photons to target tumors. Four patients were involved in this study. For the first three patients, computed tomography images acquired at exhale and inhale were available; they were registered using B-spline deformation model and the computed transformation was further used to simulate intermediate states between exhale and inhale. For the fourth patient, 4D-acquired, phase-sorted datasets were available and each dataset was registered with the exhale dataset. The exhale-inhale transformation was also used to simulate intermediate states in order to compare the cumulative doses computed using the actual and the simulated datasets. Doses to each state were calculated using the Dose Planning Method (DPM) Monte Carlo code and dose was accumulated for scoring on the exhale anatomy via the transformation matrices for each state and time weighting factors. Cumulative doses were estimated using increasing numbers of intermediate states and compared to simpler scenarios such as a "2-state" model which used only the exhale and inhale datasets or the dose received during the average phase of the breathing cycle. Dose distributions for each modeled state as well as the cumulative doses were assessed using dose volume histograms and several treatment evaluation metrics such as mean lung dose, normal tissue complication probability, and generalized uniform dose. Although significant "Point dose" differences can exist between each breathing state, the differences decrease when cumulative doses are considered, and can become less significant yet in terms of evaluation metrics depending upon the clinical end point. This study suggests that for certain "clinical" end points of importance for lung cancer, satisfactory predictions of accumulated total dose to be received by the distorting anatomy can be achieved by calculating the dose to but a few (or even simply the average) phases of the breathing cycle. (c) 2007 American Association of PhYsicists in Medicine.