Oncology Institute of Southern Switzerland, Medical Physics Unit, Bellinzona.
Radiat Oncol. 2011 Aug 26;6:103. doi: 10.1186/1748-717X-6-103.
A new algorithm for photon dose calculation, Acuros XB, has been recently introduced in the Eclipse, Varian treatment planning system, allowing, similarly to the classic Monte Carlo methods, for accurate modelling of dose deposition in media. Aim of the present study was the assessment of its behaviour in clinical cases.
Datasets from ten breast patients scanned under different breathing conditions (free breathing and deep inspiration) were used to calculate dose plans using the simple two tangential field setting, with Acuros XB (in its versions 10 and 11) and the Anisotropic Analytical Algorithm (AAA) for a 6MV beam. Acuros XB calculations were performed as dose-to-medium distributions. This feature was investigated to appraise the capability of the algorithm to distinguish between different elemental compositions in the human body: lobular vs. adipose tissue in the breast, lower (deep inspiration condition) vs. higher (free breathing condition) densities in the lung.
The analysis of the two breast structures presenting densities compatible with muscle and with adipose tissue showed an average difference in dose calculation between Acuros XB and AAA of 1.6%, with AAA predicting higher dose than Acuros XB, for the muscle tissue (the lobular breast); while the difference for adipose tissue was negligible. From histograms of the dose difference plans between AAA and Acuros XB (version 10), the dose of the lung portion inside the tangential fields presented an average difference of 0.5% in the free breathing conditions, increasing to 1.5% for the deep inspiration cases, with AAA predicting higher doses than Acuros XB. In lung tissue significant differences are found also between Acuros XB version 10 and 11 for lower density lung.
Acuros XB, differently from AAA, is capable to distinguish between the different elemental compositions of the body, and suggests the possibility to further improve the accuracy of the dose plans computed for actual treatment of patients.
最近，在 Eclipse 瓦里安治疗计划系统中引入了一种新的光子剂量计算算法 Acuros XB，它类似于经典的蒙特卡罗方法，可以准确地模拟介质中的剂量沉积。本研究的目的是评估其在临床病例中的表现。
使用来自 10 名在不同呼吸条件（自由呼吸和深吸气）下扫描的乳腺癌患者的数据集，使用 Acuros XB（版本 10 和 11）和各向异性解析算法（AAA）为 6MV 射线计算简单的两个切线野剂量计划。Acuros XB 的计算结果为剂量到介质分布。研究了这一特性，以评估该算法区分人体不同元素组成的能力：乳房中的小叶组织与脂肪组织、肺中的低密度（深吸气条件）与高密度（自由呼吸条件）。
对两种密度与肌肉和脂肪组织相容的乳房结构进行分析，发现 Acuros XB 和 AAA 之间的剂量计算平均差异为 1.6%，AAA 预测的剂量高于 Acuros XB，用于肌肉组织（小叶乳房）；而脂肪组织的差异可以忽略不计。从 AAA 和 Acuros XB（版本 10）之间的剂量差异计划直方图中可以看出，在自由呼吸条件下，切线野内肺部分的剂量平均差异为 0.5%，深吸气病例增加到 1.5%，AAA 预测的剂量高于 Acuros XB。在肺组织中，低密度肺组织中 Acuros XB 版本 10 和 11 之间也存在显著差异。
Acuros XB 与 AAA 不同，能够区分身体的不同元素组成，并表明有可能进一步提高为实际治疗患者计算的剂量计划的准确性。
