Validation of Varian's AAA algorithm with focus on lung treatments
Validation of Varian's AAA algorithm with focus on lung treatments
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DOI：
10.1080/02841860802287108
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发表时间：
2009-01-01
期刊：
影响因子：
3.1
通讯作者：
Hoffmann, Lone
中科院分区：
文献类型：
--
作者：
Ronde, Heidi S.;Hoffmann, Lone
导论.本研究的目的是检查各向异性分析算法（AAA）的准确性。针对AAA算法测试了均匀和非均匀介质（肺几何结构）中的各种不同射野配置。它也被测试对目前的双波束卷积（PBC）算法。材料和方法。二维（2D）剂量分布测量了各种不同的字段配置在固体水中的2D阵列的离子室。在带有Gafchromic剂量测定胶片的胸肺体模中测量选定横向切片中患者特定治疗计划的剂量分布。使用Farmer离子室检查Thorax体模中的点剂量。对于2D阵列测量和胶片测量，使用剂量为3%的伽马标准和3 mm的一致性距离（DTA）评价2D剂量分布。结果对于AAA，在均匀介质中测试的所有场均符合标准，但楔形和强度调制计划的非对称场除外，其中分别观察到5%和4%的偏差。总体而言，胸体模中AAA的测量和计算的2D剂量分布显示出良好的一致性-对于6和15 MV光子。在高剂量区域中超过80%的点符合伽马标准，尽管在低剂量和梯度下它失败了。对于PBC算法，只有30-70%的点符合伽马标准。结论AAA算法已被证明是优于上级PBC算法在异构介质中，特别是对于15 MV。对于大多数治疗计划，肺和纵隔区域的偏差低于3%。然而，该算法可能会低估脊髓的剂量高达7%。
Introduction. The objective of this study was to examine the accuracy of the Anisotropic Analytical Algorithm (AAA). A variety of different field configurations in homogeneous and in inhomogeneous media (lung geometry) was tested for the AAA algorithm. It was also tested against the present Pencil Beam Convolution (PBC) algorithm. Materials and methods. Two dimensional (2D) dose distributions were measured for a variety of different field configurations in solid water with a 2D array of ion chambers. The dose distributions of patient specific treatment plans in selected transversal slices were measured in a Thorax lung phantom with Gafchromic dosimetry films. A Farmer ion chamber was used to check point doses in the Thorax phantom. The 2D dose distributions were evaluated with a gamma criterion of 3% in dose and 3 mm distance to agreement (DTA) for the 2D array measurements and for the film measurements. Results. For AAA, all fields tested in homogeneous media fulfilled the criterion, except asymmetric fields with wedges and intensity modulated plans where deviations of 5 and 4%, respectively, were seen. Overall, the measured and calculated 2D dose distributions for AAA in the Thorax phantom showed good agreement - both for 6 and 15 MV photons. More than 80% of the points in the high dose regions met the gamma criterion, though it failed at low doses and at gradients. For the PBC algorithm only 30-70% of the points met the gamma criterion. Conclusion. The AAA algorithm has been shown to be superior to the PBC algorithm in heterogeneous media, especially for 15 MV. For most treatment plans the deviations in the lung and the mediastinum regions are below 3%. However, the algorithm may underestimate the dose to the spinal cord by up to 7%.