Alhakeem E, AlShaikh S, Rosenfeld A B, Zavgorodni S
Dept. of Physics & Astronomy, University of Victoria, Victoria, BC, Canada.
Centre for Medical Radiation Physics, University of Wollongong, Australia.
Med Phys. 2012 Jul;39(7Part2):4619. doi: 10.1118/1.4740086.
The purpose of this study was to examine the accuracy of AcurosXB and AAA algorithms near low and high density heterogeneities of different densities using EBT2 film, MOSFET detector "MOSkin" and Monte Carlo calculations using BEAMnrc/DOSXYZnrc. Three different interfaces were used that included a solid water phantom with 2×2×30cm rectangular air gap, rectangular steel insert, and a slab of water embedded between two slabs of lung material. 6MV photon beam with field size of 10×10cm was used for the first two geometries and a 3×3cm -field was used for the third. Percentage Depth Doses were measured and calculated at the beam central axis. Calculation voxel of 0.1×0.1×0.1cm was used by all three algorithms. For all configurations, AcurosXB and AAA agreed to within ±1.3% with MC before the inhomogeneity. The PDD measurements using MOSkin and EBT2 in water, apart from 0.2cm layer near heterogeneity, agreed with the MC within ±2.2%. Within 0.1cm before the water-air interface AcurosXB and AAA overestimated the dose by 4.7% and 1.6%, respectively. Whereas, in the 0.1cm beyond the air-water interface, AcurosXB and AAA overestimated the dose by 2.4% and 16.2% respectively. In the 0.1cm before the water-steel interface, AcurosXB overestimated the dose by 4.7% and AAA underestimated the dose by 9.5%; beyond the steel-water interface AcurosXB and AAA overestimated the dose by 3.6% and 7.7% respectively. For the lung phantom configuration, AcurosXB and AAA were in agreement with MC within 2% throughout the phantom. These results demonstrate improved performance of AcurosXB as compared to AAA in considered conditions.
本研究的目的是使用EBT2胶片、MOSFET探测器“MOSkin”以及使用BEAMnrc/DOSXYZnrc进行的蒙特卡罗计算，来检验AcurosXB和AAA算法在不同密度的低、高密度异质性附近的准确性。使用了三种不同的界面，包括带有2×2×30cm矩形气隙的固体水模体、矩形钢插件以及嵌入两块肺材料之间的水板。前两种几何结构使用场大小为10×10cm的6MV光子束，第三种使用3×3cm的场。在射束中心轴上测量并计算百分深度剂量。所有三种算法均使用0.1×0.1×0.1cm的计算体素。对于所有配置，在不均匀性之前，AcurosXB和AAA与蒙特卡罗计算结果在±1.3%以内相符。在水中使用MOSkin和EBT2进行的百分深度剂量测量，除了在异质性附近的0.2cm层外，与蒙特卡罗计算结果在±2.2%以内相符。在水 - 空气界面之前0.1cm处，AcurosXB和AAA分别将剂量高估了4.7%和1.6%。而在空气 - 水界面之后0.1cm处，AcurosXB和AAA分别将剂量高估了2.4%和16.2%。在水 - 钢界面之前0.1cm处，AcurosXB将剂量高估了4.7%，AAA将剂量低估了9.5%；在钢 - 水界面之后，AcurosXB和AAA分别将剂量高估了3.6%和7.7%。对于肺模体配置，AcurosXB和AAA在整个模体内与蒙特卡罗计算结果在2%以内相符。这些结果表明，在所考虑的条件下，与AAA相比，AcurosXB的性能有所改善。
