Zavan Rodolfo, McGeachy Philip, Madamesila Joseph, Villarreal-Barajas Jose-Eduardo, Khan Rao
Department of Medical Physics, Tom Baker Cancer Center, Calgary, AB, Canada.
Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA.
J Appl Clin Med Phys. 2018 May;19(3):32-43. doi: 10.1002/acm2.12299. Epub 2018 Mar 25.
The transport-based dose calculation algorithm Acuros XB (AXB) has been shown to accurately account for heterogeneities primarily through comparisons with Monte Carlo simulations. This study aims to provide additional experimental verification of AXB for clinically relevant flattened and unflattened beam energies in low density phantoms of the same material. Polystyrene slabs were created using a bench-top 3D printer. Six slabs were printed at varying densities from 0.23 to 0.68 g/cm , corresponding to different density humanoid tissues. The slabs were used to form different single and multilayer geometries. Dose was calculated with Eclipse™ AXB 11.0.31 for 6MV, 15MV flattened and 6FFF (flattening filter free) energies for field sizes of 2 × 2 and 5 × 5 cm . EBT3 film was inserted into the phantoms, which were irradiated. Absolute dose profiles and 2D Gamma analyses were performed for 96 dose planes. For all single slab configurations and energies, absolute dose differences between the AXB calculation and film measurements remained <3% for both fields in the high-dose region, however, larger disagreement was seen within the penumbra. For the multilayered phantom, percentage depth dose with AXB was within 5% of discrete film measurements. The Gamma index at 2%/2 mm averaged 98% in all combinations of fields, phantoms and photon energies. The transport-based dose algorithm AXB is in good agreement with the experimental measurements for small field sizes using 6MV, 6FFF and 15MV beams adjacent to various low-density heterogeneous media. This work provides preliminary experimental grounds to support the use of AXB for heterogeneous dose calculation purposes.
基于传输的剂量计算算法Acuros XB（AXB）已被证明主要通过与蒙特卡罗模拟比较来准确考虑不均匀性。本研究旨在为相同材料的低密度模体中临床相关的扁平和平坦化束能量提供AXB的额外实验验证。使用台式3D打印机制作聚苯乙烯板。以0.23至0.68 g/cm的不同密度打印了六块板，对应于不同密度的人体组织。这些板用于形成不同的单层和多层几何形状。使用Eclipse™ AXB 11.0.31计算了2×2和5×5 cm射野尺寸下6MV、15MV扁平束和6FFF（无均整器）能量的剂量。将EBT3胶片插入模体中并进行照射。对96个剂量平面进行了绝对剂量分布和二维伽马分析。对于所有单板配置和能量，在高剂量区域，AXB计算与胶片测量之间的绝对剂量差异在两个射野中均保持<3%，然而，在半影区内观察到较大差异。对于多层模体，AXB的百分深度剂量在离散胶片测量值的5%以内。在所有射野、模体和光子能量组合中，2%/2 mm的伽马指数平均为98%。基于传输的剂量算法AXB与使用6MV、6FFF和15MV束在各种低密度异质介质附近的小射野尺寸的实验测量结果吻合良好。这项工作为支持将AXB用于异质剂量计算目的提供了初步的实验依据。
