An automated optimization strategy to design collimator geometry for small field radiation therapy systems.
An automated optimization strategy to design collimator geometry for small field radiation therapy systems.
复制标题
用于设计小场放射治疗系统准直器几何结构的自动优化策略。
DOI：
10.1088/1361-6560/abeba9
复制
发表时间：
2021
影响因子：
3.5
通讯作者：
LooJr,BillyW
中科院分区：
文献类型：
--
作者：
Wang,Jinghui;Wang,Lei;Maxim,PeterG;LooJr,BillyW
PurposeTo开发一种自动优化策略，以促进准直器设计的小野放疗system.Methods和MaterialsWe开发了一个目标函数，链接的剂量分布特性（半高宽，半影，和中央剂量率）和治疗头的几何参数（准直器厚度/半径，源到远端准直器距离（SDC））的小野放疗系统。我们使用一个下坡单纯形算法进行优化。我们将此优化策略应用于基于直线加速器的放射外科系统，以确定四个准直器的最佳几何形状，以产生5，10，15和20 mm直径的光子束（来自6.7 MeV，2.1 mm FWHM电子束）。进行了两种不同的优化，以优先考虑每个射束尺寸的最小半影或最大中心剂量率。我们将优化的几何参数和剂量分布与现有的临床系统进行了比较结果当以最小半影为优先时，使用与CyberKnife系统相同的准直器厚度和SDC（40 cm），优化后的准直器上、下游半径与CyberKnife系统的一致性在3%~ 14%之间，优化后的输出因子在0%~ 8%之间，优化的横向和百分比深度剂量分布与CyberKnife的剂量分布相匹配，半影区的一致性在2%以内。然而，当最大剂量率被优先考虑时，允许准直器厚度和SDC两者改变，较大准直器尺寸（10、15、20 mm）的中心剂量率可以以1.5 - 2倍大的半影为代价增加约1.5 - 2倍。没有进一步改善中央剂量率为5 mm的光束尺寸could achieved.ConclusionsWe开发了一种自动优化策略来设计准直器的几何形状为小野放射治疗系统。使用这种策略，半影优先的剂量分布和几何参数与CyberKnife系统一致，表明该系统旨在优先考虑尖锐的半影。这表示自动优化策略可以应用于具有多个优化参数的更复杂的准直器设计的原理证明。
PurposeTo develop an automated optimization strategy to facilitate collimator design for small-field radiotherapy systems.Methods and MaterialsWe developed an objective function that links the dose profile characteristics (FWHM, penumbra, and central dose rate) and the treatment head geometric parameters (collimator thickness/radii, source-to-distal-collimator distance (SDC)) for small-field radiotherapy systems. We performed optimization using a downhill simplex algorithm. We applied this optimization strategy to a linac-based radiosurgery system to determine the optimal geometry of four pencil-beam collimators to produce 5, 10, 15, and 20 mm diameter photon beams (from a 6.7 MeV, 2.1 mm FWHM electron beam). Two different optimizations were performed to prioritize minimum penumbra or maximum central dose rate for each beam size. We compared the optimized geometric parameters and dose distributions to an existing clinical system (CyberKnife).ResultsWhen minimum penumbra was prioritized, using the same collimator thickness and SDC (40 cm) as a CyberKnife system, the optimized collimator upstream and downstream radii agreed with the CyberKnife system within 3%–14%, the optimized output factors agreed within 0%–8%, and the optimized transverse and percentage depth dose profiles matched those of the CyberKnife with the penumbras agreeing within 2%. However, when maximum dose rate was prioritized, allowing both the collimator thickness and SDC to change, the central dose rate for larger collimator sizes (10, 15, 20 mm) could be increased by about 1.5–2 times at the cost of 1.5–2 times larger penumbras. No further improvement in central dose rate for the 5 mm beam size could be achieved.ConclusionsWe developed an automated optimization strategy to design the collimator geometry for small-field radiation therapy systems. Using this strategy, the penumbra-prioritized dose distribution and geometric parameters agree well with the CyberKnife system as an example, suggesting that this system was designed to prioritize sharp penumbra. This represents proof-of-principle that an automated optimization strategy may apply to more complex collimator designs with multiple optimization parameters.