Room: Exhibit Hall
Purpose: We performed a dosimetric comparisons between the Acuros XB (AXB) and the anisotropic analytical algorithm (AAA) in RapidArc plans for high-grade glioma (HGG) which has heterogeneous region such as the skull and the air.
Methods: We analyzed 14 patients with HGG treated by RapidArc (60 Gy/30 fraction) using the AAA (ver. 11.0) at our hospital between April 2016 and January 2017. The RapidArc plans were re-optimized using the AXB (ver. 11.0) under the same conditions of dose constrains for the planning target volumes (PTVs) and organs at risk (OARs). For the newly created AXB plans, â€œdose-to-mediumâ€? was selected as dose reporting mode. The PTV60Gy was evaluated by dividing it into the skull (PTV60Gy_skull), the air (PTV60Gy_air), and the soft-tissue region (PTV60Gy_soft-tissue). The Wilcoxon signed-rank test was used for dosimetric comparison between the AAA and the AXB plans (Î±=0.05). Pearsonâ€™s moment correlation analysis was also used in order to evaluate the difference in D95% of PTV60Gy in both plans for the PTV60Gy_skull and the PTV60Gy_air.
Results: The D95% of the PTV60Gy, the PTV60Gy_skull and the PTV60Gy_soft-tissue for the AXB plans were significantly lower than those for the AAA plans in 0.9 Gy (p<0.05), 1.5 Gy (p<0.05) and 0.7 Gy (p<0.05). In contrast, the D95% of the PTV60Gy_air for the AXB plans were significantly higher than those for the AAA plans in 0.9 Gy (p<0.05). The dose of the CTV60Gy and the OARs were comparable with both plans. A correlation (R=0.50) was found in the relationship between the difference in D95% of the PTV60Gy in both plans and volume of the skull contained in the PTV60Gy.
Conclusion: In RapidArc plans for HGG, dose differences between the AAA and the AXB plans were observed, especially in the skull and the air region. Hence the calculation algorithm should be chosen carefully.