Experimental and Monte Carlo characterization of a dynamic collimation system prototype for pencil beam scanning proton therapy.
Experimental and Monte Carlo characterization of a dynamic collimation system prototype for pencil beam scanning proton therapy.
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DOI：
10.1002/mp.14453
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发表时间：
2020-10
期刊：
影响因子：
3.8
通讯作者：
Culberson WS
中科院分区：
文献类型：
--
作者：
Smith BR;Pankuch M;Hyer DE;Culberson WS
低能铅笔束扫描（PBS）的能量专用准直器的开发，以减少侧向半影的兴趣越来越大。动态准直系统（DCS）是最近出版的几部作品的焦点之一，它通过在扫描的质子束接近目标边缘时拦截一组正交修剪刀片来提供能量特异性准直。虽然一些计算研究表明，这种动态准直器可以提供额外的健康组织保护，但还没有任何严格的实验工作来对这些初始研究中使用的理论模型进行基准测试。因此，这项工作的目的是展示一种实验方法，该方法可以将实验原型与临床PBS系统相结合，并对用于模拟DCS的蒙特卡罗方法进行基准测试。一个实验DCS原型设计和建造在一个良好的表征实验设置中，在PBS期间主动准直单个质子束。蒙特卡罗方法最初用于评估施工公差，后来根据测量结果进行基准测试，包括整体深度剂量和横向不对称光束剖面。实验装置和测量几何模型使用MCNP6基准，该基准来自芝加哥西北质子中心的测量。采用伽玛分析试验，以严格的1 mm/1%标准和5%剂量阈值评估测量剖面和模拟剖面之间的一致性。模拟剖面与实测剖面非常吻合，其中积分深度剂量（IDD）剖面和横向剖面的1 mm/1%伽马分析通过率分别至少为100%和95%。在实验中观察到光束沿轴和离轴准直时相对轮廓形状的差异，这是由于光束通过非聚焦准直器的部分传输造成的。通过测量仪器监测装置激活产生的暴露率，发现与蒙特卡洛估计的暴露率一致，在20%以内。构建了DCS原型并将其集成到临床给药系统中。虽然这项工作的结果并不详尽，但它们证明了扫描过程中波束源发散、器件激活和波束偏转的影响，这些影响被发现可以使用蒙特卡罗方法成功建模并进行实验基准测试。在PBS中，模拟和测量的准直光束在轴上和离轴上的横向光斑分布之间取得了很好的一致性。蒙特卡罗模型从准直器的低能散射中充分预测了积分深度-剂量剖面中测量到的高原高架区域。
There has been a growing interest in the development of energy-specific collimators for low-energy pencil beam scanning (PBS) to reduce the lateral penumbra. One particular device that has been the focus of several recent published works is the dynamic collimation system (DCS), which provides energy-specific collimation by intercepting the scanned proton beam as it nears to target edge with a set of orthogonal trimmer blades. While several computational studies have shown that this dynamic collimator can provide additional healthy tissue sparing, there has not been any rigorous experimental work to benchmark the theoretical models used in these initial studies. Therefore, it was the purpose of this work to demonstrate an experimental method that could integrate an experimental prototype with a clinical PBS system and benchmark the Monte Carlo methods that have been used to model the DCS. An experimental DCS prototype was designed and built in house to actively collimate individual proton beamlets during PBS within a well-characterized experimental setup. Monte Carlo methods were initially used to assess construction tolerances and later benchmarked against measurements, including integral depth dose and lateral asymmetric beamlet profiles. The experimental apparatus and measurement geometry were modeled using MCNP6 benchmarked from measurements performed at the Northwestern Chicago Proton Center. Gamma analysis tests were used to evaluate the agreement between the measured and simulated profiles with a strict 1 mm/1% criteria and 5% dose threshold. Excellent agreement was observed between the simulated and measured profiles, which included 1 mm/1% gamma analysis pass rates of at least 100% and 95% for the integral depth dose (IDD) profiles and lateral profiles, respectively. Differences in the relative profile shape were observed experimentally between beamlets collimated on- and off-axis, which was attributed to the partial transmission of the beam through an unfocused collimator. Exposure rates resulting from the activation of the device were monitored with survey meter measurements and were found to agree with Monte Carlo estimates of the exposure rate to within 20%. A DCS prototype was constructed and integrated into a clinical dose delivery system. While the results of this work are not exhaustive, they demonstrate the effects of beam source divergence, device activation, and beamlet deflection during scanning, which were found to be successfully modeled using Monte Carlo methods and experimentally benchmarked. Excellent agreement was achieved between the simulated and measured lateral spot profiles of collimated beamlets delivered on- and off-axis in PBS. The Monte Carlo models adequately predicted the measured elevated plateau region in the integral depth-dose profiles from the low-energy scatter off the collimators.
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影响因子：
3.5
作者：
Castriconi, Roberta;Ciocca, Mario;Russo, Paolo
通讯作者：
Russo, Paolo
影响因子：
3.5
作者：
Lin, Liyong;Ainsley, Christopher G.;McDonough, James E.
通讯作者：
McDonough, James E.
影响因子：
3.5
作者：
Martisikova, Maria;Jaekel, Oliver
通讯作者：
Jaekel, Oliver
DOI：
10.1016/j.ejmp.2017.01.011
发表时间：
2017-02-01
影响因子：
3.4
作者：
Russo, S.;Mirandola, A.;Ciocca, M.
通讯作者：
Ciocca, M.
影响因子：
3.5
作者：
Schwaab, J.;Brons, S.;Parodi, K.
通讯作者：
Parodi, K.