Use of a realistic breathing lung phantom to evaluate dose delivery errors
Use of a realistic breathing lung phantom to evaluate dose delivery errors
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DOI：
10.1118/1.3496356
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发表时间：
2010-11-01
期刊：
影响因子：
3.8
通讯作者：
Lingos, Tania
中科院分区：
文献类型：
--
作者：
Court, Laurence E.;Seco, Joao;Lingos, Tania
目的：比较实际临床条件下不同治疗方法呼吸诱导运动对给药剂量的影响（相互作用）。方法：基于实际肿瘤的计算机断层扫描（CT）图像，使用快速原型技术创建柔性树脂肿瘤模型。将20个微型mosfet植入肿瘤模型，将肿瘤模型植入拟人呼吸假体。幻影运动是根据实际病人的运动轨迹编程的。获得一幅四维CT图像，并使用不同的治疗技术和计划系统创建了几种治疗方案：适形（Eclipse）、步进-发射调强放疗（IMRT） （Pinnacle）、步进-发射调强放疗（XiO）、动态调强放疗（Eclipse）、复杂动态调强放疗（Eclipse）、混合调强放疗[60%适形、40%动态调强放疗（Eclipse）]、体积调制弧线治疗（VMAT）[单弧（Eclipse）]、VMAT[双弧（Eclipse）]和复合调强放疗（Eclipse）。复杂的计划是通过人为地推动优化器给出复杂的多叶准直器序列来创建的。每个IMRT场照射5次，每个VMAT场照射10次，每次照射从呼吸周期中的随机点开始。通过将测量到的剂量随机相加来计算分馏的效果。计算每个分数的每个测量点的最大偏差以及95%的模型肿瘤剂量偏差小于2%和5%的概率作为分数数的函数。计算并比较各治疗方案的肿瘤控制概率。结果：经过5次分组后，除复杂动态IMRT、步进射击IMRT （XiO）、复杂VMAT和单弧VMAT方案外，所有方案中95%以上的肿瘤模型测量点的测量剂量偏差均小于2%。将复合IMRT计划的剂量率从600 MU/min降低到200 MU/min，使剂量偏差小于2%。除复杂的单弧VMAT计划外，所有计划的剂量偏差均小于5%。结论：快速成型技术可用于制作逼真的肿瘤模型。对于大多数治疗技术，剂量偏差在几次分数后平均。异常复杂的多叶准直器序列处理有较大的剂量偏差。对于IMRT治疗，可以通过降低剂量率来减少剂量偏差。对于VMAT治疗，使用两个弧线而不是一个弧线可以有效地减少剂量偏差。(C) 2010年美国医学物理学家协会。(DOI: 10.1118/1.3496356)
Purpose: To compare the effect of respiration-induced motion on delivered dose (the interplay effect) for different treatment techniques under realistic clinical conditions.Methods: A flexible resin tumor model was created using rapid prototyping techniques based on a computed tomography (CT) image of an actual tumor. Twenty micro-MOSFETs were inserted into the tumor model and the tumor model was inserted into an anthropomorphic breathing phantom. Phantom motion was programed using the motion trajectory of an actual patient. A four-dimensional CT image was obtained and several treatment plans were created using different treatment techniques and planning systems: Conformal (Eclipse), step-and-shoot intensity-modulated radiation therapy (IMRT) (Pinnacle), step-and-shoot IMRT (XiO), dynamic IMRT (Eclipse), complex dynamic IMRT (Eclipse), hybrid IMRT [60% conformal, 40% dynamic IMRT (Eclipse)], volume-modulated arc therapy (VMAT) [single-arc (Eclipse)], VMAT [double-arc (Eclipse)], and complex VMAT (Eclipse). The complex plans were created by artificially pushing the optimizer to give complex multileaf collimator sequences. Each IMRT field was irradiated five times and each VMAT field was irradiated ten times, with each irradiation starting at a random point in the respiratory cycle. The effect of fractionation was calculated by randomly summing the measured doses. The maximum deviation for each measurement point per fraction and the probability that 95% of the model tumor had dose deviations less than 2% and 5% were calculated as a function of the number of fractions. Tumor control probabilities for each treatment plan were calculated and compared.Results: After five fractions, measured dose deviations were less than 2% for more than 95% of measurement points within the tumor model for all plans, except the complex dynamic IMRT, step-and-shoot IMRT (XiO), complex VMAT, and single-arc VMAT plans. Reducing the dose rate of the complex IMRT plans from 600 to 200 MU/min reduced the dose deviations to less than 2%. Dose deviations were less than 5% after five fractions for all plans, except the complex single-arc VMAT plan.Conclusions: Rapid prototyping techniques can be used to create realistic tumor models. For most treatment techniques, the dose deviations averaged out after several fractions. Treatments with unusually complicated multileaf collimator sequences had larger dose deviations. For IMRT treatments, dose deviations can be reduced by reducing the dose rate. For VMAT treatments, using two arcs instead of one is effective for reducing dose deviations. (C) 2010 American Association of Physicists in Medicine. [DOI: 10.1118/1.3496356]