Dynamically accumulated dose and 4D accumulated dose for moving tumors
Dynamically accumulated dose and 4D accumulated dose for moving tumors
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DOI：
10.1118/1.4766434
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发表时间：
2012-12-01
期刊：
影响因子：
3.8
通讯作者：
Zhu, X. Ronald
中科院分区：
文献类型：
--
作者：
Li, Heng;Li, Yupeng;Zhu, X. Ronald
目的：探讨运动肿瘤照射的动态累积剂量（dynamic dose）与4D累积剂量（4D dose）的关系，量化肿瘤运动引起的剂量不确定性。方法：无论何种给药方式和给药性质，多次给药后，动态剂量会趋近于四维剂量，而不是三维静态剂量。分别建立了四维剂量和静态剂量的动态剂量边界，即四维剂量和静态剂量的最大估计误差。通过(1)数值模拟证明了对于每一阶段，在多次分娩后，任何给定时间的平均分娩次数收敛于总分数(K) /相数(N)的原理；(2)研究四维剂量与动态剂量之间的剂量差与“脉冲束”输送次数的关系；(3)研究4D剂量与动态剂量的剂量差随“连续束”输送时间的变化规律。建立了一种泊松模型来估计脉冲束和连续束的平均剂量误差作为输送次数或输送时间的函数。结果：数值模拟证实，假设随机起始阶段，每个阶段的交货数量收敛于K/N。对脉冲光束和连续光束的模拟也表明，剂量误差是递送次数和/或总递送时间的强函数，并且可能是呼吸周期的函数，这取决于递送方式。泊松模型与模拟结果吻合较好。结论：无论何种治疗方式，多胎分娩后动态累积剂量均向4D累积剂量收敛。动态剂量的界限可以用4D剂量得出的量来确定，动态剂量和4D剂量之间的平均剂量差作为递送次数和/或总递送时间的函数也被建立起来。(C) 2012年美国医学物理学家协会。[http://dx.doi.org/10.1118/1.4766434]
Purpose: The purpose of this work was to investigate the relationship between dynamically accumulated dose (dynamic dose) and 4D accumulated dose (4D dose) for irradiation of moving tumors, and to quantify the dose uncertainty induced by tumor motion.Methods: The authors established that regardless of treatment modality and delivery properties, the dynamic dose will converge to the 4D dose, instead of the 3D static dose, after multiple deliveries. The bounds of dynamic dose, or the maximum estimation error using 4D or static dose, were established for the 4D and static doses, respectively. Numerical simulations were performed (1) to prove the principle that for each phase, after multiple deliveries, the average number of deliveries for any given time converges to the total number of fractions (K) over the number of phases (N); (2) to investigate the dose difference between the 4D and dynamic doses as a function of the number of deliveries for deliveries of a "pulsed beam"; and (3) to investigate the dose difference between 4D dose and dynamic doses as a function of delivery time for deliveries of a "continuous beam." A Poisson model was developed to estimate the mean dose error as a function of number of deliveries or delivered time for both pulsed beam and continuous beam.Results: The numerical simulations confirmed that the number of deliveries for each phase converges to K/N, assuming a random starting phase. Simulations for the pulsed beam and continuous beam also suggested that the dose error is a strong function of the number of deliveries and/or total deliver time and could be a function of the breathing cycle, depending on the mode of delivery. The Poisson model agrees well with the simulation.Conclusions: Dynamically accumulated dose will converge to the 4D accumulated dose after multiple deliveries, regardless of treatment modality. Bounds of the dynamic dose could be determined using quantities derived from 4D doses, and the mean dose difference between the dynamic dose and 4D dose as a function of number of deliveries and/or total deliver time was also established. (C) 2012 American Association of Physicists in Medicine. [http://dx.doi.org/10.1118/1.4766434]