Halcyon<sup>TM</sup> Acuros XB vs AAA: A RapidArc Planning Comparison for Head & Neck Cancers

Abstract

The Halcyon O-ring gantry linear accelerator from Varian Medical Systems is delivered with a hardcoded beam-source model and Analytical Anisotropic Algorithm dose calculation algorithm as standard, while the Acuros XB algorithm is a purchasable option. The models in both algorithms are factory-configured and do not permit fine-tuning by the user. In this study, we compared the two algorithms for sequential boost RapidArc treatment planning of Head & Neck cancers using D98%, D95%, D50%, D2% and maximum dose to assess dose coverage of nodal and tumor planning target volumes (PTV_N and PTV_T, respectively), and cochlear D5%, parotid D20%, D50%, mean dose, and cord maximum dose to evaluate doses to organs- at-risk. The conformity index (CI), homogeneity index (HI) and total number of monitor units (MU) quantified plan quality. We found statistically significant differences in PTV_N D2%, maximum dose, HI, PTV_T D98%, D95%, D2%, Max, HI, and total MU. Statistically significant differences in Cochlear D5% and Parotid mean doses were also encountered. These differences may not necessarily be clinically significant, however. Therefore, we believe that both calculation algorithms are adequate for RapidArc planning of Head & Neck cancers.