Room: AAPM ePoster Library
Modern radiation therapies such as intensity-modulated radiation therapy (IMRT) and volume modulated arc therapy (VMAT) demand from dose calculation algorithms higher accuracy and computation speed. The goal of this study was to verify the dosimetric performance of Acuros XB (AXB, Varian Medical Systems, Palo Alto, CA) in VMAT plans and compared to the calculation algorithm of the previous version, Anisotropic Analytical Algorithm (AAA, Varian Medical Systems, Palo Alto, CA).
Ninety-five complex VMAT plans for different pathologies planned using Eclipse treatment planning system (TPS). For all VMAT plans, the dose distributions were calculated using AAA and two dose reporting modes in AXB (dose-to-water, AXBw, and dose-to-medium, AXBm) with same plan parameters. For dosimetric evaluation, the dose-volumetric parameters were calculated for each planning target volume (PTV) and interested organs at risk. The differences between AAA and AXB were statistically calculated with paired t-test.
The AAA and AXBw DVHs were close and AXBm showed varied in case of prostate and head & neck, which did not exceed within 2.0%. However, the DVHs AXBw and AXBm were similar for OAR because AXBm are based on each material. The maximum planning target volume (PTV) calculated by AAA was trended to be overestimated with relative dose difference by 3.23% in lung case. The absolute mean values of the relative dose differences were 1.1±1.2% and 2.0±1.2% when comparing between AAA and AXBw, and AAA and AXBm, respectively
The dose difference between AAA and AXB are small in regions that have densities close or low to water. The AXB is more accurate than the AAA for dose predictions when air medium is involved. Our results show that dose calculated to medium by AXB can be used clinically.