Analytic IMRT dose calculations utilizing Monte Carlo to predict MLC fluence modulation.
Analytic IMRT dose calculations utilizing Monte Carlo to predict MLC fluence modulation.
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利用蒙特卡罗分析 IMRT 剂量计算来预测 MLC 注量调节。
DOI：
10.1118/1.2178449
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发表时间：
2006
期刊：
影响因子：
3.8
通讯作者：
Siebers,JV
中科院分区：
文献类型：
--
作者：
Mihaylov,IB;Lerma,FA;Wu,Y;Siebers,JV
设计了一种混合剂量计算方法，可以准确地计算调强放射治疗（IMRT）剂量计算中多叶准直器（MLC）诱导的强度调制。该方法采用蒙特卡罗（MC）建模来确定由动态或多段（步进和射击）MLC场的传递引起的通量调制，并使用传统的剂量计算算法来估计传递给幻影或患者的剂量。因此，在解析方法包含MLC叶片迁移和散射的所有细节的限度内，决定了解析方法所能达到的IMRT影响预测精度。通过与幻影膜内剂量测量、两种内部剂量计算和两种商业处理计划系统分析影响估计方法的比较，验证了混合方法的有效性和基准性。所有的计算方法都使用相同的剂量算法来计算幻象的剂量，仅在入射光子能量影响的MLC调制估计中有所不同。伽马分析，相对于测量的二维（2D）剂量平面，用于基准测试每个算法的性能。分析的领域包括静态和动态测试模式，以及10个DMLC IMRT治疗方案（79个领域）和5个SMLC治疗方案（29个领域）的领域。试验场（全封闭的MLC、尖桩栅栏、不同大小的滑动窗和叶尖轮廓）涵盖了IMRT期间MLC使用的极端情况，而患者场则代表了现实的临床情况。在所测试的方法中，混合方法最准确地再现了测量结果。对于混合方法，79个DMLC油田计算中有79个计算的点数超过95%（每个油田），而对于SMLC油田，29个计算中有27个通过了相同的标准。分析能量影响估计方法的通过率较低，79个DMLC中有76个，29个SMLC中有24个的测试点的通过率超过95%。配对的单因素方差分析结果发现，混合方法更好地预测了两个标准的点的分数和平均伽马值。这些结果量化了当MC用于模拟MLC场调制时，IMRT剂量计算精度的提高。
A hybrid dose‐computation method is designed which accurately accounts for multileaf collimator (MLC)‐induced intensity modulation in intensity modulated radiation therapy (IMRT) dose calculations. The method employs Monte Carlo (MC) modeling to determine the fluence modulation caused by the delivery of dynamic or multisegmental (step‐and‐shoot) MLC fields, and a conventional dose‐computation algorithm to estimate the delivered dose to a phantom or a patient. Thus, it determines the IMRT fluence prediction accuracy achievable by analytic methods in the limit that the analytic method includes all details of the MLC leaf transport and scatter. The hybrid method is validated and benchmarked by comparison with in‐phantom film dose measurements, as well as dose calculations from two in‐house, and two commercial treatment planning system analytic fluence estimation methods. All computation methods utilize the same dose algorithm to calculate dose to a phantom, varying only in the estimation of the MLC modulation of the incident photon energy fluence. Gamma analysis, with respect to measured two‐dimensional (2D) dose planes, is used to benchmark each algorithm's performance. The analyzed fields include static and dynamic test patterns, as well as fields from ten DMLC IMRT treatment plans (79 fields) and five SMLC treatment plans (29 fields). The test fields (fully closed MLC, picket fence, sliding windows of different size, and leaf‐tip profiles) cover the extremes of MLC usage during IMRT, while the patient fields represent realistic clinical conditions. Of the methods tested, the hybrid method most accurately reproduces measurements. For the hybrid method, 79 of 79 DMLC field calculations have for more than 95% of the points (per field) while for SMLC fields, 27 of 29 pass the same criteria. The analytic energy fluence estimation methods show inferior pass rates, with 76 of 79 DMLC and 24 of 29 SMLC fields having more than 95% of the test points with . Paired one‐way ANOVA tests of the gamma analysis results found that the hybrid method better predicts measurements in terms of both the fraction of points with and the average gamma for both and criteria. These results quantify the enhancement in accuracy in IMRT dose calculations when MC is used to model the MLC field modulation.