Experimental and Monte Carlo verification of Acuros XB calculations near low and high density heterogeneities
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 2x2x30cm3 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 10x10cm2 was used for the first two geometries and a 3x3cm2-field was used for the third. Percentage Depth Doses were measured and calculated at the beam central axis. Calculation voxel of 0.1x0.1x0.1cm3 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.