Difference in dose‐volumetric data between the analytical anisotropic algorithm, the dose‐to‐medium, and the dose‐to‐water reporting modes of the Acuros XB for lung stereotactic body radiation therapy

The purpose of this study was to evaluate the difference in dose‐volumetric data between the analytical anisotropic algorithms (AAA) and the two dose reporting modes of the Acuros XB, namely, the dose to water ( AXB −Dw) and dose to medium ( AXB −Dm) in lung stereotactic body radiotherapy (SBRT). Thirty‐eight plans were generated using the AXB −Dmin Eclipse Treatment Planning System (TPS) and then recalculated with the AXB −Dwand AAA, using identical beam setup. A dose of 50 Gy in 4 fractions was prescribed to the isocenter and the planning target volume (PTV) D95%. The isocenter was always inside the PTV. The following dose‐volumetric parameters were evaluated; D2%, D50%, D95%, and D98% for the internal target volume (ITV) and the PTV. Two‐tailed paired Student's t‐tests determined the statistical significance. Although for most of the parameters evaluated, the mean differences observed between the AAA, AXB −Dmand AXB −Dwwere statistically significant ( p < 0.05 ), absolute differences were rather small, in general less than 5% points. The maximum mean difference was observed in the ITV D50% between the AXB −Dmand the AAA and was 1.7% points under the isocenter prescription and 3.3% points under the D95 prescription. AXB −Dmproduced higher values than AXB −Dwwith differences ranging from 0.4 to 1.1% points under isocenter prescription and 0.0 to 0.7% points under the PTV D95% prescription. The differences observed under the PTV D95% prescription were larger compared to those observed for the isocenter prescription between AXB −Dmand AAA, AXB −Dmand AXB −Dw, and AXB −Dwand AAA. Although statistically significant, the mean differences between the three algorithms are within 3.3% points. PACS number(s): 87.55.x, 87.55.D‐, 87.55.dk