Room: Exhibit Hall | Forum 3
Purpose: To quantify the impact of PTV volume and amount of lung surrounding the PTV on AXB (Acuros XB) dose to water (-Dw) and dose to medium (-Dm) dose calculation in lung-SBRT.
Methods: A cohort of 25 lung-SBRT patients treated with 48 Gy/4 fractions were selected. Dose computation was performed using AAA, AXB-Dw and AXB-Dm algorithms in Eclipse version 13.6. Amount of lung surrounding PTV was quantified using ring structures (1 cm and 2 cm) around PTV booleaned with the lung structureto determine overlap with lung tissue. Multiple regression was performed to determine impact of PTV volume and lung tissue surrounding PTV on AXB-Dm and AXB-Dw as estimated by the difference between AAA and AXB-Dw, -Dm for PTV V100 (%) coverage.
Results: The ANOVA results demonstrate a significant dependence of both AXB-Dw and AXB-Dm on the amount of lung tissue surrounding PTV (p < 0.05 for both 1 cm and 2 cm ring structures). The results also demonstrate no significant dependence of PTV volume on either AXB-Dw or AXB-Dm (p > 0.05). In addition, a trend of increasing lung tissue around PTV and a higher difference in AAA and AXB-Dw, -Dm for PTV V100 (%) can be observed.
Conclusion: While the impact of target size in lung-SBRT for AXB and AAA algorithms has been discussed in the literature, there has been little discussion on target location. Clinical appraisal of AXB in variety of lung-SBRT patients demonstrates that the lung tissue surrounding the target has a much stronger influence on overall dose computation compared to target volume. The results could facilitate clinical implementation of AXB in lung-SBRT, as large changes in dose coverage are expected for central targets, which in turn may influence patient outcomes.
TH- External beam- photons: treatment planning/virtual clinical studies