Room: ePoster Forums
Purpose: To explore dosimetric effects using normal tissue optimization (NTO) and collimator optimization dedicated to SRS in HyperARC, planned dose distribution was optimized and delivered to evaluate dose discrepancy with EBT3 film.
Methods: The calibration curves of EBT3 films were obtained in different scanning parameters such as contrast and brightness. The optimal curve was determined by evaluating the range and the linearity of optical densities corresponding to the each delivered doses from 0 Gy to 26 Gy. Moreover, the positions where the errors were detected and the percentage of dose agreement were evaluated if they were close to the expected values. The dosimetric impact using the different optimal calibration curves on dose evaluation was analyzed. The dose gradients at the different isodose levels were evaluated for HyperArc plans optimized with SRS NTO.
Results: When the optimal calibration curve was applied to evaluate delivered dose distribution of the multi-target cases in HyperArc, dose gradient from 90% to 15% of the isodose level showed little difference in dose agreement. However, the calibration curve obtained in conventional scanning parameters showed the gradient difference ofmore than 3 mm at the same dose level
Conclusion: To accurately evaluate the dose gradient and agreements in SRS by film dosimetry, application of the optimal calibration curve is significant. When the optimal calibration curve of EBT3 film was used in dose evaluation of the multi-target cases, the SRS-NTO of HyperArc showed the noticeable high agreement of thedose gradient in the delivered dose distributions.
Funding Support, Disclosures, and Conflict of Interest: This study was supoorted by Varian Medical Systems.