Acuros XB advanced dose calculation algorithm (AXB, Varian Medical Systems, Palo Alto, CA) has been released recently and provided the advantages of speed and accuracy for dose calculation. For clinical use, it is important to investigate the dosimetric performance of AXB compared to the calculation algorithm of the previous version, Anisotropic Analytical Algorithm (AAA, Varian Medical Systems, Palo Alto, CA). Ten volumetric modulated arc therapy (VMAT) plans for each of the following cases were included: head and neck (H&N), prostate, spine, and lung. The spine and lung cases were treated with stereotactic body radiation therapy (SBRT) technique. For all cases, the dose distributions were calculated using AAA and two dose reporting modes in AXB (dose-to-water, AXB_w, and dose-to-medium, AXB_m) with same plan parameters. For dosimetric evaluation, the dose-volumetric parameters were calculated for each planning target volume (PTV) and interested normal organs. The differences between AAA and AXB were statistically calculated with paired t-test. As a general trend, AXB_w and AXB_m showed dose underestimation as compared with AAA, which did not exceed within −3.5% and −4.5%, respectively. The maximum dose of PTV calculated by AXB_w and AXB_m was tended to be overestimated with the relative dose difference ranged from 1.6% to 4.6% for all cases. The absolute mean values of the relative dose differences were 1.1±1.2% and 2.0±1.2% when comparing between AAA and AXB_w, and AAA and AXB_m, respectively. For almost dose-volumetric parameters of PTV, the relative dose differences are statistically significant while there are no statistical significance for normal tissues. Both AXB_w and AXB_m was tended to underestimate dose for PTV and normal tissues compared to AAA. For analyzing two dose reporting modes in AXB, the dose distribution calculated by AXB_w was similar to those of AAA when comparing the dose distributions between AAA and AXB_m.

KeywordsAcuros XB advanced dose calculation algorithm, Anisotropic Analytical Algorithm, Volumetric modulated arc therapy, Dose-volumetric parameter